FM 23 81 75mm Rifle M 20 1948

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DEPARTMENT OF THE ARMY FIELD MANUAL
Е! ЕМ 23-81
This manual supersedes those portions of Training Circulars No, 25,

War Department, 1945, and No. 11, War Department, 1946, pertaining
to the 75-mm rifle,

75-mm RIFLE
M20

° MARCH 1948

Ээ RESTRICTED. DISSEMINATION OF RESTRICTED MATTER.—No
person is entitled solely by virtue of his grade or position to

f. knowledge or possession of classified matter. Such matter

is entrusted only to those individuals whose official duties
require such knowledge or possession. (See also AR 380—5.)

United States Government Printing Office
Washington : 1948

DEPARTMENT OF THE ARMY |
Washington 25, D. C., 11 March 1948 _

FM 23-81, 75-mm Rifle, M20, is published for the
information and guidance of all concerned.

[AG 300.7 (19 Dec 47)1

By ORDER OF THE SECRETARY OF THE Army:

OMAR N. BRADLEY
Chief of Staff, United States Army
OFFIGIAL:
EDWARD F. WITSELL
Major General
The Adjutant General

DISTRIBUTION:

USAF (10); AGF (40); OS Maj Comd (2);
Base Comd (2); MDW (11); Arm & Sv Bd
(2); Tech Sv (2); Sch (50) except Inf Sch
(1500); USMA (50); ROTC (1); A (ZI)
(25), (Overseas) (10); CHQ (10); D (3);
B (2); R2 5, 7; 17 (2); Bn 2, 5572122);
C 2, 5, 7, 9, 17 (1) ; Five (5) copies to each of
the following: T/O & E 7-18; 7-26; 3-36T ;
7-58T.

For explanation of distribution formula see TM

38-405.

(

CONTENTS
$ Paragraphs Page
CHAPTER 1. INTRODUCTION ............... MeL 1
CHAPTER 2. MECHANICAL TRAINING.
Section I. Disassembly and assembly ....... 4-6 4
II. Mechanical functioning .......... 7-8 10
III. Stoppages and immediate action.. 9-11 17
IV. Ammunition and fuzes ........... 12-18 22
V. Careand cleaning ............... 19-20 31
VI. Mountings eder uox. ese ese 21-22 38
VII. Fire control instruments ......... 23-31 40
VIII. Equipment, spare parts, and ac-
CeSSOTIGS VUES E T vais ves voie sa 32-33 51
CHAPTER 3. TRAINING FOR PLACING GUN IN
ACTION.
Section I. Crew drill ........ "IO ERO Soc 34-44 56
II. Battery drill ..... ELS mos ... 45-46 67
CHAPTER 4. MARKSMANSHIP.
Séctionris, "General О 47-49 69.
II. Preparatory exercises ........... 50-58 70
Tie Boresighting е «6» v 59 79
IV. Qualification courses ............ 60-64 82
À V. Safety precautions and procedure
E for firing ..... Җае Кас ‚... 65—69 91
CHAPTER 5. TECHNIQUE OF DIRECT FIRE.
Section T^ uneneralo а.е ++» 70-72, -101
II. Characteristics of fire ......... . 72-75 101
III. Range determination ...... .. 76-82 105

Section IV.
V.

VI.

VII.

VIII.

TX:

X.
XI.

CHAPTER 6.

Section 1.
II.
ПІ.

IV.

VII.
IX.

XI.

CHAPTER 7.
Section 1.

Paragraphs

Speed and lead determination .... 83-85
Target designation ............., 86-90
«Birescontrolie ое vie . 91-94
TFareicommands 0066 95-101
Range cards ueteres nere imis 102
Direct laying on landscape targets,

VU UE ose CODO T "odo adt 103-109
iDransition firing ее 110-112
ДеП firme. or «vis de Si oE АЕО 113-116
TECHNIQUE OF INDIRECT FIRE.

Сепега т о settee аен 117-118
Computation of initial data ...... 119-124
General principles of conduct of

ате ое еа е 125-135
Conduct of бге by range-bracket-

ING procedure. „шли уена е. 136-141
Conduct of fire by deflection-

bracketing procedure .......... 142-149
Conduct of the battery ......... 150-156
Prearranged fires ............... 157-159
Position defilade ................ 160-164
Extract of fire control tables....165-166
Recorders sheet ................ 167-168

Subcaliber training on landscape
targets at unknown short ranges169-175

ADVICE TO INSTRUCTORS.

(serleral зеден ала 176-179
Mechanical training ............. 180-185
Crew аги жааганы 186-187
Marksmanship 5 188-189
еа бше тендан Еле атаа 190-192

193
195

197 ( |f
198

199

201

] This manual supersedes those portions of Training Circulars
No. 25, War Department, 1945, and No. 11, War Department,
1946, pertaining to the 75-mm rifle.

CHAPTER 1
INTRODUCTION

$, RESTRICTED

1. PURPOSE AND SCOPE. a. This manual pro-
vides the unit commander with the data necessary
for the step-by-step training of gun crews equipped
with the 75-mm rifle, M20.

b. The scope of this manual includes mechanical
training, training for placing the gun in action,
marksmanship, and the techniques of direct and in-
direct fire.

2. DESCRIPTION. a. The 75-mm rifle, M20 (fig. 1),
is a recoilless portable weapon designed to be fired
from the machine gun tripod mount caliber .30,
M1917A1. It is an air cooled, single shot, breech
loading weapon using fixed ammunition. This rifle
is equipped with a manually operated breech mech-
anism and a percussion type firing mechanism.
b. Tabulated data. (1) General.

> Weight of rifle (w/sight bracket)...... Ibs 114.5
Weight of rifle complete w/mount and
siPhbracket jon dee pd d rre Ibs 167.7
Wen ethno ril sees spoke eee ere ess in 82
пепео tube, о: іп 65.1
Бейек ОН ay ИЗО in 65.1
Type of breechblock ........... Interrupted screw

Figure 1. 75-mm rifle M20 (mounted on HMG tripod).

(2) Performance.
Muzzle velocity HE and WP.......... f/s 990
Muzzle velocity HEAT .............- f/s 1000
Range (approximate maximum) :
Cartridge, HEAT, N310 (T39),

for 75-mm rifle, M20 ............ yds 7200
Cartridge, HE, M309 (T38), )

for 75-mm rifle, М20 ............ yds 6955 (
Cartridge, SMOKE, WP, M311 (T40),

fon 75-mimrifie; М0 yds 7020

c. Data pertaining to mount M1917A1. See FM
23-55.
d. Sighting equipment: (1) Unit sight, M34 (for
indirect fire), consists of—
Elevation quadrant.
2

Telescope adapter.
Elbow telescope.

Instrument light.
Carrying case.
(2) Direct fire sight, M85C, consists of—
Telescope mount.
Telescope.
Instrument light.
Carrying case.

3. PRINCIPLE OF OPERATION. The shell cas-
ing for recoilless rifle ammunition is perforated so
that the propellant gases can escape through the
perforations into the enlarged chamber of the’ tube.
The breech is so constructed that, on ignition of the
propellant charge, the resultant gases are allowed
to escape to the rear through orifices in the breech-
block, thereby eliminating recoil. The gas escape
orifices are so designed that the momentum of gas
discharge effectively counteracts the momentum of
recoil and the angular momentum induced by the
motion of the fired shell, and the rifle remains
motionless.

CHAPTER 2
MECHANICAL TRAINING

Section I. DISASSEMBLY
AND ASSEMBLY

4. GENERAL. A knowledge of the procedure of
disassembly and assembly is a prerequisite to an
understanding of functioning and stoppages, and
to an ability to perform immediate action to reduce
stoppages. The process of normal care and cleaning
also requires a knowledge of these subjects. The
following paragraphs outline a standardized, step-
by-step method of disassembly and assembly.

5. DISASSEMBLY (fig. 2). The Allen wrenches
contained in the breech handle are the only tools
needed to field strip the rifle. The preliminary
steps and the disassembly of the parts are accom-
plished in the order indicated below.

a. Disengage the breech lock, open the breech q
and check the chamber to see that it is clear. With \3
the breech in the open position, rotate the safety
and depress the trigger. Holding the trigger de-
pressed, close the breech. This places the hammer
and firing spring in the “as fired” position.

b. Remove the two breech operating handle

lousing screws on the left side of the breech
perating handle housing, and remove the lower
screw on the right side. Holding the right hand in
position to catch the closéd breech lock spring
in the event that it springs out of its seat, remove

1. Tube chamber assembly. 13. Trigger spring.
2. Vent bushing. 14. Safety.
_ 3. Breechblock 15. Sear cover.
4. Breech operating handle hous- 16. Sear.
ing screws. 17. Cam rollers.
(5. Extractor and extractor spring. 18. Breech hinge, hinge pin and
6. Breech operating handle as- hinge pin screw.
sembly. 19. Breech hinge block, shim and
7. Firing spring. screws.
8. Hammer and firing pin. 20. ) Front mounting bracket
9. Breech handle cap. 21. | and screws.
10. Closed breech lock and spring. 22. Front mounting bracket ring.
11. Trigger. 23. Telescope mount and screws.
12. Trigger pin. 24. Tube handle assembly.

Figure 2. 75-mm rifle, M20—disassembled.

the remaining screw, and remove the breech oper-
ating handle housing assembly. tl

c. Remove the closed breech lock and spring.

d. Remove the firing pin, hammer assembly, and
the firing spring from the hammer housing.

e. Remove the two cam rollers from the hammer
housing.

f. Lift out the sear cover.

g. Rotate the safety 14 turn counterclockwise,
depress the trigger, continue the counterclockwise
rotation of the safety for another 14 turn, then lift
out the trigger safety assembly, being careful not
to displace the trigger key from its recess.

h. Remove the sear.

i Rotate the breechblock to the unlocked posi-
tion and open the breech. Lift the breechblock off
the hinge.

j. Withdraw the extractor from its seat in the
hinge, and then withdraw the extractor spring.

k. Remove the cam rollers from the hinge.

1. Remove the hinge pin screw from the hinge
block and remove the hinge pin by pushing it out
of the block.

m. The weapon is now stripped for normal care
and cleaning. There are three additional ili
blies which may be undertaken, under competen
supervision, for periodic cleaning. They are:

(1) Separation of firing pin from hammer. Insert
hammer into its seat in the housing, making sure
that the square slots in the hammer engage the
cam rollers. While supporting housing with one

he spanner wrench.

(2) Removal of breechblock hinge. Rotate hinge up-
ward to uncover the hinge block screw. Using
small wrench unscrew the hinge block screw. Dis-
engage the hinge from the hinge block by remov-
ing the hinge pin.

(3) Disassembly of the trigger and safety assembly.
(a) While holding the base of the trigger, slightly pull
up and rotate the trigger safety, and allow the
trigger key to drop out of the trigger.

(b) Holding trigger safety in left hand, with the
trigger spring down, place corner of cover plate
against the end of trigger spring. Exert pressure
against the end of spring to prevent it from turn-
ing. Rotate trigger safety counterclockwise and
unscrew it from trigger spring. Withdraw trigger
safety from trigger.

(c) Hold trigger in left hand and, using the same
procedure as outlined in (b) above, remove trigger
spring from trigger.

n. The removal of tube carrying handles, the
mounting bracket, and the telescope mount may be

. accomplished, under competent supervision, by
poc or unscrewing the proper clamping or

j hand unscrew the firing pin from hammer using

olding screws.

o. The vent bushing is screwed into the rear
end of the chamber and locked in place by the
hinge pin screw which passes through the chamber
wall into a hole in the bushing. The cone and the
interrupted threads, which engage the breechblock,
are an integral part of the bushing. These parts

may be removed by ordnance maintenance person-
nei only. (

6. ASSEMBLY. Assembly is in approximately the
reverse order of disassembly.

a. Place the hinge in position so that it straddles
the hinge block, and insert the hinge pin so that
the notch in the pin faces to the rear.

b. Insert and tighten the hinge pin screw making
certain that the point on the screw enters the hole
in the vent bushing.

c. Replace the cam rollers in the hinge.

d. Insert the extractor spring into its recess in
the hinge. This spring may be inserted with the
curved surface either up or down.

e. Insert the extractor into the recess in the
hinge so that the hook is pointing away from the
hinge block.

f. Place the breechblock on the hinge making
certain that the projection on the lower end of the
extractor enters the cam slot in the breechblock.

g. Close the breech and rotate the breechblock
to the locked position.

h. Replace the sear in its slot in the breech
operating handle housing so that the tapered end
is toward the hammer housing and the bent cn
is in the trigger handle.

i. Insert the trigger and safety assembly into
the trigger handle so that the studs of the safety
become engaged in the slots in the trigger handle.
Revolve the trigger key clockwise until it is lined
up with the lugs on the safety, In order to com-

igger. Before this assembly can be fully seated
in the trigger handle, the sear recess in the base
of the trigger must be in position to receive the
bent end of the sear. When the assembly is com-
pletely seated, the safety will revolve and retain
the assembly.

»- this operation it is necessary to depress the

j. Place the sear cover, curved end up, over the
sear slot in the breech operating handle housing.

k. Replace the two cam rollers in their recesses
in the hammer housing.

1. Center the’ firing spring in the hammer hous-
ing. Place the hammer-firing pin assembly over the
firing spring with the cam rollers positioned in the
two square slots, and with the sear notch in posi-
tion to engage the sear.

Caution: Be sure that the hammer is replaced
so that the sear notch is opposite the sear. If the
hammer is replaced backwards—that is, so that
the sear notch is opposite the closed breech lock—
the closed breech lock will engage the hammer in
the cocked position when the piece is cocked.
Manual operation of the closed breech lock will
then release the hammer. This situation is ex-
tremely dangerous if the breech is closed on a live
ound, as the only way the breech may be reopened
s by disengaging the closed breech lock manually.

m. Replace the closed breech lock and spring
into their recess in the breech operating handle
assembly.

n. Holding the closed breech lock pin, place the
breech operating handle assembly against the

breechblock so that the trigger handle is on the

left. \(
о. Secure the assembly to the breechblock with `

the four breech operating handle assembly screws.
p. Replace tools in breech handle and replace
breech handle cap.
q. Test by cocking the piece and actuating the
firing mechanism.

Section II.
MECHANICAL FUNCTIONING

7. GENERAL. a. Introduction. A gun crew, to be
efficient, must be able to keep its gun in action
during combat. Therefore, in order to recognize
the causes of mechanical failures, and to reduce
the stoppages resulting therefrom, the crew must
have a working knowledge of the mechanical func-
tioning of the gun.

b. To unload. The gunner opens the breech by
rotating the breechblock clockwise (using the trig-
ger handle only) through an angle of approx-
imately 45°, and then withdraws the breech assem-
bly from the chamber. The loader grasps the
partially extracted round by hand and ejects it.

с. To load. The loader inserts a round of ammu-
nition into the chamber engaging the preengraved
rotating band with the lands and grooves of the
tube.- The loader replaces the breechblock in the
chamber and rotates it (using the breech handle
only) counterclockwise to the locked position.

d. To fire the piece. The gunner rotates the

safety clockwise (using either the index or middle
nger of the right hand) as far as it will go, and
en depresses the trigger with his thumb.

e. To clear the gun. The gunner opens the
breech; the loader checks the chamber to see that
the piece is unloaded. The piece is clear as long
as the breech is open and the chamber is empty.

8. FUNCTIONING. For purposes of instruction,
the subject of functioning is divided into three
main headings which are: opening the breech,
closing the breech, and firing the piece. Since
functioning is a cycle, it is necessary to choose
some point in the cycle from which to start. In
the paragraphs on functioning which follow it is
assumed that the piece has just been fired and
that the empty shell case is still in the chamber.
With this situation existing, successive steps in
operation of the piece are—

a. Opening the breech (fig. 3). (1) Cocking. The
cam rollers in the hammer housing hold the ham-
_ mer so that when the breech operating handle

assembly is rotated, the Һатте1 must also rotate.
The hammer is free to move horizontally back
and forth independently of the breech operating
handle assembly. When the breech operating
«handle assembly is properly positioned against

he breechblock, the cam rollers in the hinge are
lined up with the square slots in the hammer.
When the breech operating handle assembly is
rotated clockwise, the cocking cams on the ham-
mer come into contact with the cam rollers in
the hinge, and since these are immovable, the

hammer is forced to the rear against the action
of the firing spring. When the hammer has be]
cammed to the rear approximately one-half inch; /
the sear notch has moved into position so that
the sear can be cammed to the right by the cam-
ming action of the oblique hole in the base of the
trigger against the bent end of the sear. This
camming action is actuated by the trigger spring
which has a tendency to draw the base of the
trigger up. The sear then enters the sear notch,
and engages the hammer in the cocked position.
When the breechblock has been rotated clockwise
through approximately 45°, the piece has been
cocked.

(2) Unlocking. When the breechblock has rotated
clockwise through approximately 45°, the inter-
rupted screws on the breechblock become disen-
gaged or unscrewed from their locking Surfaces
in the chamber, and the breech is unlocked.
Rotation is stopped when the right arm of the
breech operating handle assembly comes in con-
tact with the built-up portion of the hinge.

Note.—There are two unlocking actions. One is as described
immediately above; the other is the disengaging of the closed
breech lock from the hinge as described in c(1) below.

(3) Extraction. When the breechblock is in the
closed and lock position, the hook of the extractor,
is positioned in front of and below the rim of the
shell case. As the breech is rotated to the open posi-
tion, the extractor is cammed upward by the cam-
ming action of the cam slot in the rear face of the
breechblock against the large end of the extractor
pin. This action so positions the extractor hook that

when the breechblock is swung to the rear, the
ook engages the rim of the cartridge case, with-
rawing it about two inches from the chamber
before the hook is swung out of position by the
downward movement.

(4) Breech lock open. The action of locking the
breechblock, so that it may not be rotated while
in the open position, is performed by the extractor
arm. When the breech is open the extractor arm
is forced into a recess in the rear of the breech-
block by the action of the extractor spring, thereby
locking the breechblock to the hinge. The purpose
of this action is to insure that when the breech-
block is placed into the chamber the threads оп
the breechblock will not burr against their locking
surfaces im the chamber.

b. Closing the breech. (1) Action of the breech
lock open. When the breechblock is closed the hook of
the extractor first comes into contact with the rim
of the shell case, or with the cone if the piece is
not loaded, and is cammed away from the center
of the breechblock against the action of the ex-
tractor spring. This camming action forces the
arm of the extractor out of the recess in the rear
of the breechblock, and thereby breaks the con-
nection between the breechblock and the hinge,
so that the breechblock is free to be rotated coun-
terclockwise to the locked position.

(2) Action of the extractor. When the breechblock
is fitted into the chamber, the extractor hook comes
into contact with the rim of the shell case and
is momentarily cammed to the side of the case.
When the breechblock is fully seated, the extrac-

tor hook snaps into position in front of the rim
of the shell case and remains there until the”
counterclockwise rotation of the breechblock is
begun, at which time it is cammed downward by
the action of the cam slot in the rear face of the
breechblock acting against the large end of the
extractor pin.

(3) Locking. When the breech is rotated counter-
clockwise the interrupted screws on the breech-
block engage with their locking surfaces in the
chamber. When this rotation is complete the cut-
away portion of the breech lock cam on the ham-
mer is in position to receive the small end of the
closed breech lock. The small end of the closed
breech lock is then forced into the cutaway portion
of the closed breech lock cam by the action of the
closed breech lock spring. When the closed breech
lock is in this position, the shoulder of the lock
bridges the gap between the breech operating
handle assembly and the hinge, thereby preventing
rotation of the breechblock. By moving the closed
breech lock pin to the right, the breech can be
unlocked without actuating the firing mechanism.

c. Firing the piece. (1) Action of the firing mech-
anism (fig. 3). The safety is a sleeve with slots in it.
' The slots are so arranged that the rotation of the
safety alines the longitudinal slot with the trigger
key so that the trigger may be depressed. As the
trigger is depressed, the oblique hole (sear recess)
in the base of the trigger acts as a cam against
the bent end of the sear, camming the sear away
from the hammer. As the sear becomes disengaged
from the sear notch in the hammer, the hammer

f the firing spring. (Rotation of the safety puts
a tension on the trigger spring which tends to
return the safety to its original position. Depres-
sion of the trigger also puts a tension on the
trigger spring which tends to return the trigger
to its original position. When the trigger is drawn
up to the firing position the sear is cammed to
the right. The trigger and safety do not return
to their firing positions until the piece is recocked
because the sear cannot be cammed to the firing
position unless the sear notch is in position to
receive the tapered end of the sear.) As the ham-
mer goes forward, the closed breech lock cam on
the hammer cams the closed breech lock to the
right, disengaging the shoulder of the closed
breech lock from its recess in the hinge, thus un-
locking the block so that it is free to be rotated
to the open position. The firing spring drives the
hammer firing pin assembly forward so that the
firing pin strikes the primer with sufficient force
to detonate it, and the piece is fired. SEE

(2) Action of the gases. When the propellant charge
is detonated, a chemical reaction transforms the
solid powder into a mass of hot gases which

y ruptures or burns its way through the

>: pin assembly moves forward under the action

‘raft paper container within the shell case, and
escapes through the perforations. The gases expand
in all directions with equal force. The force exerted
against the end of the projectile sends it through
the tube. The force exerted in the opposite direc-
tion sends the gases through the gas escape orifices
in the breechblock. The escape orifices are so

. 15

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-. adjusted in size and shape that the forward and
earward thrusts acting on the tube chamber as-

М embly neutralize each other. The orifices аге also
canted so that the gases are given a twisting
motion to the rear. The resulting rotational thrust
on the tube is equal and opposite to the rotational
thrust caused by the action of the projectile against
the rifling of the tube.

Section III. STOPPAGES AND
IMMEDIATE ACTION

9. DEFINITIONS. a. A stoppage is any uninten-
tional cessation of fire.

b. Immediate action is the unhesitating proced-
ure used for the prompt elimination of common
stoppages.

10. STOPPAGES. a. Prevention of stoppages.
With a knowledge of functioning and care and clean-
ing the gunner can eliminate stoppages, to a large
extent, by taking proper care of his piece and by
performing detailed inspections from time to time.
Prevention is the best remedy for all stoppages.

b. Causes of stoppages. Listed below are com-
mon stoppages and their usual causes. Although
not considered stoppages in the literal sense of

Q- word, two common malfunctions, forward
movement and recoil, have been included at the
end of the list. (See (6) (а) and (b) below.)

(1) Failure to fire. (a) Defective ammunition.

(b) Broken firing pin.

(d) Carbon on firing pin shoulders.

(e) Carbon in firing pin recess.

(f) Breech not fully locked. A

(g) Trigger frozen. ,

(h) Incorrect assembly of hammer.

(2) Failure to cock. (a) Weak, broken, or discon-
nected trigger spring.

(b) Insufficient rotation of breechblock.

(3) Failure of breech to open. (a) Closed breech
lock engaged with hinge (piece not fired).

(b) Incomplete rotation of breechblock.

(4) Failure to extract. (a) Broken or missing ex-
tractor spring.

(b) Broken extractor hook.

(5) Failure of breech to close and lock. (a) Broken
or missing extractor spring allowing premature rota-
tion of breechblock.

(b) Extractor frozen in position, allowing prema-
ture rotation of breechblock.

(d) Preengraved rotating band burred causing im-
proper positioning of round in chamber. f

(e) Fouling in throat of tube causing TEA
positioning of round in chamber.

(f) Fouling of breechblock. threads or locking
surfaces.

(g) Misalinement of threads because of shifted
hinge block.

hen fired — obstruction in gas escape orifices.

4 (6) General malfunction of operation. (a) Recoil

(b) Forward movement when fired — gas escape
orifices too large. (To be corrected by ordnance
maintenance personnel only.)

11. REDUCTION OF STOPPAGES.

a. Immediate action.

Gun fails to fire

No. 1 releases pressure on trigger and calls “Misfire.”
No. 2 examines breech lock pin to determine whether

hammer has fallen.

If hammer fell, No. 2
waits 30 seconds then
recocks by rotating
breech operating
handle assembly.

No. 1 fires.

Piece still fails to fire.

If primer dented,
No. 2 reloads with
у” round.

If primer is not dented,
No. 2 tests firing mecha-
nism with breech open.
Replaces defective part.

If hammer did not fall

No. 2, using stick or other
object, forces closed breech
lock pin away from hammer
housing, opens breech, un-
loads. Holding breechblock
in relative firing position
with breech open, No.2 tests
firing mechanism,

If trigger depresses prop-
erly, firing spring or sear
is broken, Replace firing
spring or sear.

If trigger cannot be depressed,
trigger is improperly assembled
or there is obstruction in
trigger handle. Check trigger
assembly and handle. Replace
defective parts or reassemble.

lined in a above does not place the gun in action,
the gunner must inspect the working parts of the
gun to locate and reduce the stoppage. Table below
lists less common stoppages and actions by which
the stoppage can be reduced.

b. Uncommon stoppages. If the procedure out- 4

Stoppage Indication Action

Gun fails to} Closed breech | No. 2 attempts to recock mak-

cock. lock pin fe- ing sure breech operating
mains in handle assembly is rotated
unlocked clockwise as far as it will go.

position.
Gun still fails | Closed breech | No. 2 removes breech operat-
to cock, lock pin re- ing handle assembly and
mainsin checks assembly of hammer,
unlocked checks cam rollers, sear, and
position, trigger spring. Replaces de-

fective part or reassembles.

Breech fails to | Breech fails | №. 2 calls for No. 1 to remove
open, to open. hand from trigger handle.
No. 2 then checks closed

breech lock pin. If hammer

has not fallen, he proceeds

as in paragraph 10a above.

If hammer has fallen, No. 2

checks to see if breech op-

erating handle assembly has

turned far enough to disen-

gage breechblock screw

from locking surfaces ii

chamber.
Gun fails {о | No. 2 cannot | No. 2 examines extractor hook,
extract. grasp empty tests the extractor for free-
shell case. dom of movement, strength

of spring; replaces defective
part or cleans out foreign
matter,

Stoppage Indication Action

eech fails to | Breech fails to| No. 2 checks breechblock for

close and | to close and premature rotation. Checks
lock. lock. extractor for freedom of

movement; checks to see if
extractor is alined with ex-
tractor clearance cut; cor-
rects extractor deficiencies
by replacement or reassem-
bly. If extractor is correct,
No. 2 checks to see that am-
munition is seated properly;
checks fouling in throat of
tube and on threads of
breechblock and locking sur-
face; cleans out fouling. If

there is no fouling, No. 2

checks hinge block for prop-
er position; if shifted, gun

must be repaired by higher
echelon.

Malfunction: | Gun recoils No. 2 removes obstruction
gun recoils. when fired. from gas escape orifices.
(Note. New guns sometimes
recoil slightly when first
fired. When this is the case,
recoil can be partially coun-
terbalanced or taken up by
reversing the tripod so that
the trail leg is to the rear.
Erosion of the vent bushing
during normal firing will
then balance the gun, after
which the tripod should be
returned to its original posi-
tion. Caution must be ob-

served to see that back blast

does not undermine the trail
leg when tripod is reversed).

Malfunction: | Gun moves Vent bushing must be replaced
gun moves| forward by ordnance maintenance
forward| when fired. personnel.
when fired.

Section IV. AMMUNITION
AND FUZES

12. GENERAL. Ammunition for the 75-mm rifle,
M20, is issued in the form of complete, fixed rounds
(fig. 4). The round consists of a primer and propel-
ling charge in a perforated case which is crimped
rigidly to the projectile. The term “fixed” used in
connection with ammunition signifies that the pro-
pelling charge is not adjustable and that the round
is loaded into the weapon as a unit. The case is
crimped rigidly to the projectile because the round

1. High explosive. 5. Inert.

2. High explosive antitank, 6. Individual metal container.
3. Smoke, WP. 7. Individual fiber container.
4. Target practice. 8. Packing box.

Figure 4. Ammunition for the 75-mm rifle, M20.

nust be rotated in the chamber so that the pre-
pees rotating band can be fitted into the lands

nd grooves of the tube. Because of the preengrav-
ing on the rotating band, a lower chamber pres- .
sure is required to propel the round. The propellant
is contained within the casing by a thin tube of
Kraft paper. This paper is only 0.004" thick; there-
fore, caution must be observed in handling the
round to prevent rupture of this tube. Because
of the incomplete protection against moisture af-
forded by the paper, added precautions must be
taken to assure that the ammunition is kept dry.
Each round comes packed in a waterproof, hermet-
ically sealed container and should not be un-
packed until ready for use. Each round weighs
about 22 pounds. Each round in its individual
container weighs 27 pounds. Two rounds in their
wooden crate weigh 78 to 80 pounds.

13. TYPES (fig. 4). Depending upon the type of
projecticle, ammunition for this rifle is classified
as high explosive (HE), high explosive antitank
(HEAT), white phosphorus (WP), inert (IN),
and target practice (TP).

14. HIGH EXPLOSIVE. a. The HE projectile is
a comparatively thin walled projectile containing
» high explosive bursting charge. It is used princi-

ally for fragmentation or mining effects. It-has
a total weight of 14.4 pounds and contains a charge
of 1.4 pounds of TNT. It comes equipped with a
point detonating, PD M48A2 or М51А4 fuze,
either of which may be set for instantaneous (SQ)
or delayed (DELAY) detonation (fig. 5).

igure 5, Fuse PD M48A2 and M5144 for HE round,
75-тт rifle, M20,

‘ Note. The only difference between the two fuzes is the

ster charge.

ttings are made by turning a setting screw
in the side of the fuze. Setting positions marked
“DELAY” and “SQ” (superquick) are stamped
on the side of the fuze ogive (F). The setting
device is an eccentrically positioned plunger (J)
and plunger spring (K) the functioning of which
is regulated by a setting sleeve (I). The head of
the sleeve is slotted to facilitate turning when
adjusting the setting.

b. When the slot in the sleeve head is alined
with the “SQ” line, the sleeve, which is thicker
on one side than on the other, is turned so that
it does not interfere with movement of the plunger.
The plunger is free, therefore, to move outward
under centrifugal force, and thereby open the pas-
sage (G) from the head of the fuze to the booster
charge. Superquick detonation occurs when the
nose of the fuze strikes an object. The head of the
fuze (A) is crushed and the firing pin (D), which
is supported by a gilding metal cup (C), is driven
into the detonator (E) setting it off. The flash
from the detonator passes down the tube (G),
which connects the superquick action (B) to the
ody (H), and into the booster.

c. When the slot in the setting sleeve is alined
with the “DELAY” line the thick side of the
sleeve is in position to stop any outward move-
ment of the plunger, and even though the super-
quick action functions normally on impact, the
detonator flash never gets past the plunger into
the booster. On impact the delay action (L) comes

E 25

pins (Q) to recede outward, thereby leaving th
delay action mechanism free to move forward.
Centrifugal force also causes the plunger pin lock
(P) to place an arm against the inner end of each
plunger pin so that the pins are prevented from
returning to the unarmed position. On impact,
inertia causes the delay action plunger to move
forward driving the primer (N) against the firing
pin (M). The primer ignites the black powder
delay pellet (O) which in turn detonates the relay
charge (R). No action takes place upon firing until
sufficient rotational speed has been established to
overcome the resistance of springs and set back
force on the safety devices. Bore-safe superquick
action is provided by the plunger (J). Bore-safe
delay action is provided by the M20 booster for the
M48A2 fuze, and by the M21A2 booster for the
М51А4 fuze.

into play. Centrifugal force causes the ng nd

15. HIGH EXPLOSIVE ANTITANK. a. The

armor penetrating ability of a normal projectile

depends upon its weight, velocity at time of im-

pact, and angle of impact. Since muzzle velocities
| have been greatly reduced in this weapon, it is |
|| necessary to employ a shaped or hollow charge
| in order to secure armor penetration. The HEA

projectile employs such a charge. The projectile
weighs 13.1 pounds. The fuze for the projectile
is the base detonating BD M62AL (fig. 6) for which
there is no setting of delay.

b. The firing pin (K) is held in the unarmed
position in the percussion plunger by spring-held |

фей '21ї4 шш-с;

safety pins (L) which release the firing pin under
the action of centrifugal force. The percussio
plunger assembly will not arm at 1,700 revolution’
or less per minute. The slider assembly (E) is
normally positioned under spring pressure in its
recess in the fuze body so that the slider charge
(F) of the slider is out of alinement with the
other explosive elements. When sufficient centrif- +
ugal force has been set up, the slider overcomes
the resistance of the spring and moves outward,
bringing the slider charge (F) into alinement.
The slider will not arm at 2,400 revolutions or
less per minute, but must arm at 3,600 revolutions
per minute. Upon firing, and after sufficient rota-
tional force has been created, the firing pin and
slider move into the armed position. However the
percussion plunger assembly (J) is held to the rea:
during the flight of the projectile by the restrain-
ing spring (I). Upon impact, the plunger over-
comes the resistance of the springs and carrie:
the firing pin forward against the primer (H)
initiating the action of the explosive train (G)
through the booster lead (D). The booster pelle:
(B) in its turn causes detonation of the shel
bursting charge.

16. SMOKE. The smoke, WP, projectile (vein)
15.1 pounds) is used for screening smoke, ince:
diary action, limited antipersonnel action, spotting
round, or any combination of these. The filer i:
white phosphorus. The projectile has a thin wall
tubular casing, called the burster, which extend:
nearly the length of the filler cavity, and whic!

e M57 for ИР" round, 75-mm rifle, M20.

Figure 7. Fuz

contains a detonator relay chain and a burster
charge of high explosive to rupture the shell an

disperse the chemical contents. The fuze M5

(fig. 7) is essentially the M48A2 fuze modified to
a single action superquick type by omitting the
delay element, and is of the same size, shape, and
weight. There is no setting sleeve on the centrif-
ugal interrupter.

17. TARGET PRACTICE. The target practice
projectile weighs 14.4 pounds. It is made of cast
iron and has the same dimensions, weight, and
center of gravity as the HE projectile. It contains
a black powder spotting charge and is equipped
with the M51A4 fuze (fig. 5).

18. INERT. The inert projectile contains no ex-
plosive charge. It is plastic loaded to bring it up
to the weight of the HE projectile (14.4 pounds).
It is equipped with the dummy fuze M73.

Section V. CARE AND CLEANING

19. GENERAL CARE. Dirt and grit, accumulated
in traveling or from blast of the piece in firing,
form cutting compounds. Powder fouling settles
between. and on operating parts and attracts ША
ture, prevents proper operation of moving parts,
and hastens the formation of rust. Dirt, grit, and
powder fouling should be cleaned from all parts at
frequent intervals, depending upon use and service.
If rust should accumulate, its removal from bear-
ing surfaces requires special care in order that

hould be used for this purpose. The use of coarse

abrasives is strictly forbidden. When the weapons
ate not in use they should be properly oiled and
covered.

yos are not unduly increased. Crocus cloth

20. PREVENTIVE MAINTENANCE SCHED-
ULES. a. Before firing. (1) Remove and disassem-
ble the breechblock group and wipe all components
thoroughly dry.

(2) Thoroughly clean the bore and chamber of
all dirt and oil.

(3) Assemble the gun and wipe outer surfaces
with a clean, dry rag.

b. After firing. The procedures outlined below
are to be followed immediately after firing and are
to be repeated each day for three consecutive
days, or until there is no longer evidence of sweat-
ing. The materials and the cleaning and preserving
procedures to be used for recoilless weapons’
bores are indicated in order of preference below.

ГА

(1) Rifle bore cleaner. (a) Thoroughly clean the
bore with rifle bore cleaner each day for two days
after firing, making sure that all surfaces are well

)y:us Do not wipe dry.

(b) On the third day after firing, clean the bore
with rifle bore cleaner. If the piece is to be fired
within the next 24 hours, do not wipe dry until
just before firing. If the piece will not be fired
within the next 24 hours, wipe dry and coat with
the prescribed oil.

the tube has cooled to the point where it can be touched wit
the bare hand. Bore cleaner is an excellent rust preventive fo

Note. The bore should not be cleaned with bore cleaner a
periods of from 24 to 48 hours.

(c) Following the third day after firing, renew the
oil film daily. Every fifth day, clean with rifle bore
cleaner, wipe dry and oil.

(2) Soda ash. (a) Prepare a solution of 1⁄4 pound
soda ash to each gallon of warm water. In tem-
peratures below 32? F., and if the tube to be
cleaned is cold, add the type and amount of anti-
freeze prescribed in 'TM 9-850.

(b) Immediately after firing and on three consecu-
tive days thereafter, thoroughly clean the bore
with the soda ash solution. Rinse with clear warm
water and wipe dry. Coat with the prescribed oil.

(c) When the piece is not being fired, renew the
oil film daily. Every fifth day clean the bore with
dry cleaning solvent, wipe dry, and oil.

(3) Soap. (a) Use castile or issue soap. Prepare a
sponging solution by shaving 1 pound of soap into
4 gallons of water. If possible, warm the water to
facilitate dissolving the soap. In temperatures be-
low 32° F., and if the tube to be cleaned is cold,
add the type and amount of antifreeze prescribed
in TM 9-850.

(b) Follow the same cleaning, drying, and oiling
procedure prescribed for soda ash solution.

Caution: When issue soap is used, the bore must
be thoroughly rinsed after cleaning as the soap
may contain a free caustic which will cause cor-
rosion if not completely removed.

(4) Hot water. (a) As a temporary measure after

swabbing with quantities of hot water. This meth-

us the bore may be cleaned while still hot by

od will be used only when rifle bore cleaner,
soda ash, or soap is not available. After cleaning
with hot water extreme care must be taken to
dry the bore thoroughly. A coating of oil will be
applied immediately' thereafter to prevent rust.

(b) Swabbing with hot water may not remove all
of the primer salts or powder residue. It is most
important, therefore, that the bore be cleaned as
soon as possible in accordance with (1), (2), or
(3) above.

c. Chamber. The method and materials used for
cleaning the bore will be used for cleaning the
chamber. However, the bore brush is impractical
for cleaning the chamber and an improvised burlap
swab on a stick should be used.

d. Breech. The breech mechanism must be dis-
assembled, all parts cleaned and oiled, and reas-
sembled at each cleaning. Rifle bore cleaner, pref-
erably, or commercial dry cleaning solvent may
be used to clean the parts.

e. Oiling. For temperatures above 0° F., oil,
lubricating, preservative, medium, should be used
or oiling all parts; for temperatures below 0° F.,
il, lubricating, preservative, special, should be
used. See War Department Lubrication Order
9-304, Rifle, 57-mm, M18.

f. Care in the field and during combat. The same
procedures for care and „cleaning should be fol-
lowed in the field and during combat as are pre-

scribed above where the materials and the time
are available. Shortage of prescribed materials will 4
have to be dealt with by substitute measures. Í
Where none of the materials listed above are avail-
able, swabbing the bore with dampened rags fol-
lowed by thorough drying and swabbing with oily
rags will serve as an emergency measure. It must
be remembered that this treatment is a temporary
measure only, and that at the first opportunity
the weapon should be cared for as described in a
through e above.. In the event lubricants prescribed
in e above are not available the lubricants listed
below may be used as emergency substitutes :

Preservative lubricating oil (light).

Lubricating oil for aircraft instruments and
machine guns.

Engine oil, SAE 10 (above 32° F.).

g. Operation under unusual conditions. The pro-
cedures for the mechanical operation of the rifle _
are the same for operation under either usual or
unusual climatic conditions. In addition to the
|| normal preventive maintenance service specified

throughout this manual, special care in cleaning
and lubrication should be observed where extremes
| of temperatures, humidity, and atmospheric con-
| ditions are present. Proper cleaning and anctonin
|

not only insure proper operation and functioning
| but also guard against excessive wear of the work-
ing parts and deterioration of the matériel.

| (1) Cleaning in cold climates. (a) In temperatures
| below freezing, it is necessary that the working
parts of the rifle be kept absolutely free from mois-

ture. Take special care to remove excessive oil
n the working parts because it will congeal to
uch an extent as to cause sluggish operation and
functioning, or complete failure. This applies, in
particular, to the small spring-operated parts in
the breech mechanism and trigger group.

(b) Protect rifles not in use with the proper covers
to prevent frosting.

(c) Allow rifles taken into heated buildings to
come to the temperature of the building before
cleaning. Immediately after they reach room tem-
perature, disassemble to the extent outlined in
paragraph 5. Thoroughly wipe all moisture from
all parts as well as the bore and chamber to
prevent rusting. Then thoroughly clean by one of
the methods outlined above and lubricate as out-
lined.

(2) Cleaning in hot climates. (a) In hot climates,
the thin film of oil necessary for operation and
preservation will be quickly dissipated. Inspect
rifles frequently, paying particular attention to
unexposed surfaces such as the bore and chamber,
springs and spring seats, firing pin, and like places
where corrosion might occur and not be quickly
noticed. When necessary renew a film of the
oil prescribed above. Keep screws and pins lightly
be: to prevent rust from attacking them and
"freezing" them in place.

(5b) Protect rifles not in use with the proper covers.

(c) Perspiration from the hands is a contributing
factor to rusting because it contains acid. After
handling, wipe dry and restore the oil film.

(3) Cleaning under excessively sandy or dusty
conditions. (a) In localities where dust and sand
storms are prevalent, carefully protect the rifles
with proper covers. Dust and sand will enter the |
mechanism and bore and stick on lubricated sur-
faces, forming a gummy paste which may clog the
rifle and cause malfunction. This paste will also
act as an abrasive and will cause undue wear of 7
|| the moving parts of the rifle. 7

(b) Under such conditions thoroughly clean and
lubricate the rifles as often as necessary.

(c) Disassemble to the extent outlined in para-
graph 5. Clean by one of the methods outlined |
above. Lubricate with the oil specified. Apply the
oil to moving parts and contacting surfaces only.
The film of oil will be as light as possible for
proper functioning of the rifle. `

(4) Cleaning in excessively moist or salty atmos-
phere. Salt air is conducive to quick rusting as the
salt has a tendency to destroy the rust-preventive
qualities of the oil. When operating the rifle under
these conditions, treat it in a manher similar to
that prescribed for operation in hot climates.

h. Demolition to prevent enemy use. (1) The de-
struction of the matériel, when subject to capture
ог abandonment in the combat zone, will be under-:
taken by the using arm only on authority dele-
gated by the division or higher commander, as {
command function, when such action is deemed
necessary as a final resort to keep the matériel
from reaching enemy hands. The barrel assembly
and breech mechanism are the most vital parts of
this rifle. Next in importance are the mount and

gun book. Adequate destruction of this matériel
neans damaging it in such a way that the enemy

y: restore it to usable condition in the combat
zone by fepair or cannibalization. Adequate de-
struction requires that—

(a) Enough parts essential to the operation of the

matériel must be damaged.
=

(b) Parts must be damaged beyond repair in the

combat zone.

V (c) The same parts must be destroyed on all ma-

tériel, so that the enemy cannot make up one
"operating unit by assembling parts from several
„partly destroyed units.

(2) To demolish the rifle proceed as follows: >”

(a) Detach all optical sights. If evacuation is pos-
sible, carry the sights; if evacuation is not possible,
thoroughly smash the sights.

(b) Depress muzzle. Open breech. Using incendiary

. grenade M14, pull safety pin, but continue to hold
the grenade safety handle in safe position. Aline
grenade with open breech. Release safety handle
and insert grenade into the chamber. Stand clear
to the side at least 15 yards. The intense heat of
the burning incendiary grenade will damage the
chamber and molten iron will pour through the
bore and render it unserviceable.

Caution: De sure to use an incendiary grenade
and Not a fragmentation or offensive grenade.

(c) For information on demolition of ammunition,
refer to TM 9-1901. For information on demolition
Of mounts and fire control equipment refer to

FM 23-55.

Section VI. MOUNTINGS

21. TRIPOD M1917A1. The 75-mm rifle, M20, al
designed to be mounted on the Browning machine
gun tripod M1917A1 (for description see FM
23-55). Two mounting brackets are assembled on
the piece. The rear mounting bracket is at the
junction of the tube and chamber. The. front
mounting bracket is a circular removable bracket
which is clamped and tightened on the tube by
Wi means of screws. The position of the front mount-
ing bracket can be adjusted to fit the mounting
| brackets of the gun to the tripod. The gun pintle

is attached to the rear mounting bracket, and the
front mounting bracket fits over the elevating
screw head. The gun is mounted on the tripod
| with the trail leg and longer arm of the cradle to
| the front (fig. 1).

22. OTHER MOUNTINGS. Although the rifle is '
|| normally to be mounted on standard ordnance
mounts, it may be mounted on any mount that will
| take a pintle. Successful and efficient firing has
been accomplished with the gun mounted on the
|| light machine gun tripod М2 (fig. 8), and on the
pedestal and dashboard mounts of the 14-ton truck

| (fig. 9). When firing from the %4-ton truck, d
must be taken that the back blast does not damage
any part of the vehicle. The use of improvised
| mounts can be dangerous; hence the need for suf-
| ficient clearance and safety precautions must be

| emphasized.

| 38

Figure 8. 75-mm rifle, M20, mounted on light machine gun
tripod.

10406861 5

Figure 9. 75-mm rifle, M20, mounted on t-ton truck,
dashboard mount.

Section VII. FIRE CONTROL
INSTRUMENTS {

23. GENERAL. Since the 75-mm rifle M20 is capa
ble of delivering both direct and indirect fire, it is
equipped with two sights. The telescopic sight
M85C is used for direct fire for ranges up to and
including 2,100 yards. The telescopic sight M34 is
used for direct fire for ranges over 2,100. yards
and for all indirect fire.

24. SIGHT М85С. The sight M85C (fig. 10) is a
short tube telescope provided with a sunshade and
rubber eyeshield. The telescope is a fixed focus,
three-power instrument having a field of view of
119 30'. The reticle pattern (fig. 11) consists of a

Figure 10, Sight M85C for 75-mm rifle, M20.

7676064
75-НЕ. AT T39

Figure 11. Sight reticle, sight M85C.

series of broken horizontal lines and a broken
vertical line. The cross hair at the top of the pattern
represents zero deflection and zero elevation. Fach
vertical line segment and each space between
the segments represents a change in range of 100
ards. Each horizontal line segment and each space
between the segments represents an angular lead
of 5 mils. There is a dovetail slot, with a window,
on the side of the telescope. To this may be fixed
the night lighting device. The open sight which
has been built on top of the telescope is used for
quick alinement of the sight on the target.

25. SIGHT M34. The sight M34 (fig. 12) consists
essentially of three parts.

a. The lower part is the elevation quadrant
T13E1 which furnishes the means for laying the
piece in elevation. Rotating the elevation knob
elevates or depresses the angle of sighting. The
amount of elevation is registered in mils on a scale
and micrometer. The elevation scale is graduated
in 100-mil increments from minus 200 to plus 1,600,
every even graduation being numbered. The eleva-
tion micrometer is divided into two semicircles,
each graduated from 0 to 100 mils, in 2-mil incre-
ments, every fifth graduation being numbered. One
complete rotation of the micrometer will indicate
a change in elevation of 200 mils on the elevation
scale. When the longitudinal bubble is centered,
the rifle is elevated to the angle indicated on the
scale.

b. The telescope adapter M9 is the center part
of the sight. It contains the mechanism and scales
for laying the piece in direction. It has an azimuth
scale which is graduated in 100-mil increments in
two semicircles from 0 to 3,200 mils each. Every
fourth graduation is numbered. The deflection
micrometer is graduated from 0 to 100 mils in
l-mil increments, each tenth- graduation being
numbered. Azimuth or deflection is set on the scale
and micrometer by turning the azimuth worm
knob. For rapid motion in azimuth, the internal
worm and worm gear can be disengaged by push-
ing outward on the azimuth worm knob. The
adapter also contains the cross level bubble. An
open sight has been built as an integral part of

Figure 12. M34 for 75-mm rifle, M20.

the adapter and is used for quick alinement of
the sight on the target or aiming point.

c. The top part of the sight is the elbow tele-
scope M62, which is a three-power, fixed focus
instrument having a field of view of 12? 12'. The
reticle pattern consists of a vertical and a hori-

zontal line which cross at the reticle center. The
telescope is attached to the adapter in such a h
ner that, by loosening the elevation clamping
screw, the telescope can be elevated or depressed
independently of the elevating mechanism; and
by loosening the telescope clamping screw, the
telescope can be rotated about the axis of the
horizontal arm of the scope. A dovetail bracket
housing a window, on the side of the telescope,
is provided for attaching the night lighting device.

26. LENSATIC COMPASS. The lensatic compass
is standard for fire control use with the 75-mm
rifle, M20. The prismatic compass may be used
but the watch compass is unsuitable for such use.
For description and operation of the lensatic com-
pass, see FM 23-90.

27. BINOCULAR. For nomenclature, operation,
and maintenance, see TM 9-575.

28. PLOTTING BOARD N10. a. General. Com-
plete data on description and operation of the M10
ij plotting board can be found in FM 23-55.

||| b. Use. The M10 plotting board is used by per-
| sonnel of the 75-mm rifle platoon to facilitate fig-
uring of initial fire data for the 75-mm rifle, M20,
as follows: E
M (1) When the ranges involved are greater than
Il can be accommodated on the board by use of the
half value scale, any point on the disc may be
used as the OP. In such cases, ranges for plotting
OT and OG are measured parallel to the index
line with the disc set for the required azimuth.

||!
| 44

ata for GT are then obtained as usual. The

nge scale may be doubled or quadrupled, thus

ermitting use of the plotting board for longer
ranges without selecting a different point to be
used as the OP.

(2) To find fire data from a gridded map, obtain
from the map the coordinates of the OP, the gun
position, and the target. On the plotting board,
with the disc set at zero, and using the grid system
of the plotting board with any convenient grid
intersection as a common point of origin, plot co-
ordinates as read from the map on the disc.
Azimuth and range are then read as above.
Azimuths obtained will be grid azimuths, subject
to the usual correction for conversion to magnetic
azimuths.

(3) When ungridded maps or aerial photos only
are available, with north and either yard scale or
representative fraction indicated, proceed as fol-
lows: On map or photograph at a convenient
position draw in north-south and east-west lines,
their intersection to serve as point of origin for
coordinates. Coordinates of a point are obtained
by measuring its lateral offset from the north-south
line, and its vertical offset from the east-west line.
Ш a graphic yard scale is available, it is used for

easuring. Resulting coordinates are applied. di-
rectly to the grid system of the plotting board,
as above, and resulting ranges read in yards there-
on. If no graphic scale is available but the repre-
Sentative fraction is known, measurements are
made on the map or photo in inches and applied
to plotting board grid system accordingly. Result-

ing azimuths will be correct, but resulting range.
wil be in the scale of the plotting d
(v to 1000 yards or xoi) and must be converte;

to scale of the map or aerial photo by applying the
ratio between the denominator of indicated repre.
sentative fraction and that of the plotting board,
Thus, if range on the plotting board is 1500 yard;
(1.5”), and representative fraction of the phot

24000
3 20002 1500, o:

ur actual range is
24000’
1000 yards.
29. GUNNER’S QUADRANT М1 (fig. 13).

a. General. The gunner’s quadrant M1 is used i:
laying for elevation and for leveling the gun during
tests and adjustments.

or map is

Figure 13. Gunner's quadrant M1,

aped frame to which is pivoted an arm carrying

level. Notches on the frame engaging with a
plunger in the arm permit rapid setting of the
arm to elevations from 0 to 800 mils. Separate
scale and micrometer indications on opposite sides
of the quadrant are used to obtain elevation
readings.

c. Operation. (1) To lay the piece at a given
elevation, set the scale and micrometer at the
required angle and place the corresponding refer-
ence surface on the quadrant seat of the gun.
Elevate the gun slightly above the center position
of the leveling bubble, then depress it until the
bubble is centered.

(2) To measure the elevation of the gun, place
the proper reference surfaces of the quadrant on
the leveling plates, parallel to the bore, with the
associated arrow pointing in the direction of fire.
(Black arrow and black figures are for readings
from zero to 800 mils; red arrows and red figures
are for readings from 800 to 1,600 mils.) Set the,
micrometer at zero. Disengage the plunger from
the notches in the frame, lift the arm, and lower
it slowly until the bubble is seen to pass through
he central point of the level. Allow the plunger
o engage with the notches and turn the microm-
eter until the bubble is accurately centered. Face
the side of the quadrant which bears the arrow in
use, and read the scale and micrometer indica-
tions. A note engraved below the micrometer in-
dicates whether the red or black micrometer figures
‘ire to be read. The scale is divided into 10-mil

Y Description. This quadrant includes a sector
a

graduations. The micrometer is divided into 1-mi|
graduations up to 10. The elevation of the gu
in mils is equal to the sum of the scale and microm!
eter readings. Remove the quadrant from the gun
before firing.

(3) To measure depression angles, proceed a:
above, but with the line of fire arrow pointed in
the reverse direction.

d. Test and adjustment. No adjustment of the
quadrant by the using arm is permitted. The zer
position may be verified (end-for-end) by setting
the scale and micrometer at zero elevation, elevat.
ing or depressing the gun to center the bubble
then turning the quadrant end-for-end. If the bub.
ble does not remain centered, rotate the microm.
eter until it is centered. Note the reading on the
micrometer. Apply one half of the reading to the
micrometer and re-level the tube. This reading
may be used as zero

30. AIMING CIRCLE M.. i-or compete aescrip:
tion of this instrument see FM 23-90.

31. CARE AND PRESERVATION. a. General
(1) Fire control and sighting instruments will no
stand rough handling or abuse; inaccuracy or mal
functioning results from such mistreatment.

(2) Instruments are kept as dry as possible
they are not put in their carrying cases when wet

(3) When not in use, instruments are kept i:
carrying cases provided or in the condition indi
cated for traveling.

(4) Any instruments which give incorrect read

ings and/or fail to function properly after the

uthorized tests and adjustments have been made
): turned іп for repair by ordnance personnel.
Only those adjustments expressly authorized are
performed by using personnel. The turning of
screws or other parts not essential to the use of
the instrument is expressly forbidden.

(5) No painting of fire control equipment by
using personnel is permitted.

(6) Many worm drives have “throwout” mech-
anisms to permit rapid motion through large
angles. When using these mechanisms, the throw-
out lever must be fully depressed to prevent injury
to the worm and gear teeth,

(7) When using a tripod with adjustable legs,
the legs must be clamped tightly to prevent the
possibility of collapse. —

(8) When setting up tripods on sloping terrain,
two legs are placed on the downhill side to provide
maximum stability.

(9) Exposed moving parts should be oiled occa-
sionally with a small quantity of neutral oil. In-
terior parts are oiled by ordnance personnel. Any

excess lubricant that seeps from the mechanisms
is wiped off to prevent accumulation of dust and
arit.

(10) Optical instruments must not be pointed
directly at the sun.

. (11) Compass needles and dials must always be
clamped in position when not in use.

(12) Forced rotation of any of the knobs beyond

their limits must be avoided.

(13) The clamps on the aiming circle legs must
be turned outward to prevent damage to the verti-
cal support of the aiming circle when legs ar

folded.

b. Optical parts. (1) To obtain satisfactory
vision, the exposed surfaces of the lenses and other
parts should be kept clean and dry. Corrosion and
etching on glass surfaces, which greatly interfere
with the good optical qualities of the instrument,
can be prevented or minimized by keeping the
glass clean and dry.

(2) Under no condition will polishing liquids,
pastes, or abrasives be used for polishing lenses
and windows.

(3) To remove dust, the glass is brushed lightly
with a clean camel’s-hair brush; the brush is then
rapped against a hard surface to knock out the
small particles of dust that cling to the hairs. This
operation is repeated until all dust is removed.
With some instruments an additional brush with
coarse bristles is provided for cleaning mechanical
parts. Each brush is used only for the purpose
intended.

(4) Particular care will be exercised to keep
optical parts free from oil and grease. Lenses or
windows are not wiped with the fingers. To re-
move oil or grease from optical surfaces, ethyl
alcohol is applied with a clean camel’s-hair brush
afterward the surfaces are rubbed gently with clean
lens paper. If alcohol is not available, breathe heav-
ily on the glass and wipe with a clean lens paper.
This operation is repeated several times until the
lens is clean.

(5) When the temperature of the parts is lower

an that of the surrounding air, moisture may
i on the optical parts of the instrument. This
‘moisture, if not excessive, can be removed by
placing the instrument in a warm place. Heat
from strongly concentrated sources should not be
applied directly, as it may cause unequal expansion
of parts, thereby resulting in breakage or dis-
tortion of optical parts, and causing inaccuracies ,
in observation.

Section VIII. EQUIPMENT, SPARE
PARTS, AND ACCESSORIES

32. EQUIPMENT, SUBCALIBER. a. General.
Subcaliber equipment component parts are—

(1) Subcaliber device, 75-mm, complete.

(2) Firing pin, subcaliber, 75-mm.

(3) Firing pin bushing, 75-mm.

b. Description. The subcailber deviee (figs. 14
and 15) consists of a 75-mm drill cartridge T8
or 75-mm inert cartridge T38 with fuse, primer,
and igniter removed. In the base of the cartridge
case is mounted the barrel bushing. Tht projectile
is drilled through the center of the base to receive
Ep carbine barrel and barrel extension tube (essen-

ally a pipe threaded at both ends). Over the
forward portion of the barrel extension tube is fit-
ted the head space adjustment nose, which is held
in place by the barrel locking nut. The subcaliber
firing pin is the same as a normal firing pin except

that the striker has been turned down from 346”

| Figure 14. Subcaliber device assembled.

Figure 15. Subcaliber device disassembled.

to 4,4”. The firing pin bushing fits in the firing pin
| aperture and over the firing pin.

| с. Installation. Remove firing pin from hammer
| and replace with subcaliber firing pin (fig. 16).
JM Remove extractor. Assemble the rifle. Open the
al breech and insert firing pin bushing in firing pin
| aperture. Insert the subcaliber device into the

breech, match the preengraved rotating band, and
If fully seat. The device is positioned in the tube by
| the preengraved rotating band and neck of the
cartridge casing. To remove the subcaliber device,
TM unload in the same manner as service ammunition.

| d. Operation. Loading, firing and extraction;
MI Carbine cartridges are loaded by hand into thd
breech of the subcaliber device. Care must be
taken in closing the breech since the extractor
| has been removed. This allows rotation of the
Il breechblock on the hinge while in the open posi-
| tion. Undue roughness and carelessness will result
|

Figure 16. Hammer, subcaliber firing pin, and bushing.

in burring and jamming of locking surfaces. After
the breech is closed the trigger is actuated; this
causes the firing pin to move forward, guided by
the firing pin bushing, and strike the primer of
the carbine cartridge. As the propellant gases leave
the muzzle of the carbine barrel they tend to
“burble” ahead of the projectile causing inaccuracy.
The gas escape slots allow these propellant gases
to escape sidewise, thereby allowing the projectile
to travel accurately.

e. Extraction. Extraction of the carbine cartridge
hould be accomplished by use of a screw driver.
his method requires approximately the same
amount of time for extraction as that necessary
for a service round thereby simulating service
firing.

f. Targeting. The rifle will be targeted prior to
range firing. This is accomplished as follows:

(1) Fire five rounds at 1000 inches to obtain :

group.

(2) Without disturbing the lay of the A
adjust the sight so that the desired sight picture
is obtained on the center of the group.

(3) Check the sight setting by firing five more
rounds.

(4) After targeting has been completed, do not
remove the device from the chamber until com-
pletion of firing, unless necessary for headspace
adjustment.

g. Head space adjustment. Head space must be
properly adjusted prior to and during all firing.
To adjust:

(1) Loosen barrel locking nut.

(2) Turn the head space adjustment nose, screw-
ing the barrel in the barrel bushing until the pro-
jection on the breech is flush with the base of the
75-mm cartridge casing.

(3) During firing, head space will change due to
induced torque; therefore it must be checked
continuously.

(4) Caution must be observed to keep the breech

operating handle assembly screws tight, or loose
head space will occur.

(5) Ruptured cartridges should be removed only
by a carbine ruptured cartridge extractor. If the
breech is difficult to close, tight head space may
exist and cause rupturing of cartridges.

h. Care and cleaning. The device should be
cleaned after each firing and three days thereafter.

3 unit should be disassembled for cleaning. For
s of care and cleaning see paragraphs 19

ADDITIONAL EQUIPMENT. For informa-
1 on other equipment, spare parts, and artillery
book, see TM 9-314 and ORD 7, ORD 8,
id ORD 9, respectively, SNL C74.

CHAPTER 3

TRAINING FOR PLACING GUN

Section I. CREW DRILL

34. GENERAL. a. The object of crew drill is t
give the section complete confidence in its abilit
as a team to put its gun into action with precisio:
and speed.

b. The attainment of precision is the first ste;
in developing an expert section. This is achieve
only by strict adherence to prescribed trainin;
procedure. After the desired degree of proficienc;
in precision has been attained, the next phases—
teamwork and speed—are undertaken.

c. Teamwork is assured by rotation of dutie
during drill so that each section member, by prac
tice, becomes expertly acquainted with the dutie
of every other member, particularly with the mor:
detailed actions of Nos. 1, 2, and 4. Continuity o
action is made certain by this phase of training.

d. Practice for speed is instituted as the las
phase of instruction in crew drill. Care must b
taken during this phase to insure that precisio:
and teamwork are not sacrificed for speed.

ORGANIZATION AND EQUIPMENT FOR
EW DRILL (fig. 17). a. Normally, the section
ill use only one of its two organic weapons for

crew drill. The section leader is armed with an
M1 rifle and carries binoculars, compass, gunner’s
quadrant, firing tables, and the sights.

b. No. 1 is the gunner. He is armed with a pistol
and carries the tripod and cradle.

c. No. 2 is the loader. He is armed with a pistol
and assists in carrying the tube. He wears a light
pack and carries one thermite grenade.

d. No. 3 is a gunner’s assistant. He is armed
with a pistol and assists in carrying the tube. He
wears a light pack and carries one thermite
grenade.

e. No. 4 is a gunner’s assistant. He is armed
with a pistol and assists in carrying the tube. He
wears a light pack and carries one thermite
grenade.

f. No. 5 is an ammunition bearer. He is armed
with a carbine and assists in carrying the tube up
to the gun position whence he reverts to carrying
ammunition. He wears a light pack and carries
one thermite grenade.

. g. Nos. б, 7, and 8 are ammunition bearers.
bv are armed with the carbine and carry pack
oards with two rounds of ammunition. No. 8,
in addition, carries the rammer staff and waste
for swabbing out the bore. They each carry two
fragmentation grenades.

h. No. 9 is the vehicle driver (34-ton truck with
l-ton trailer). He is armed with an M1 rifle.

Figure 17. 75-mm rifle section with equipment.

36. DUTIES OF SECTION MEMBERS. a. Sec
tion leader (observer). The section leader is i:
direct command of the gun and its equipment in
cluding the vehicle. He conducts the section i:
accordance with the orders and instructions o
his platoon leader or of the commander of th
unit to which he is attached according to th
dictates of the terrain and the situation. He is re
sponsible for the care and maintenance of th
gun and its equipment. In combat he is responsibl.
for the accomplishment of the section mission
He controls and conducts the fire of the gun an
is responsible for its proper concealment. He keep:
the platoon leader informed of the status of ammu
nition supply and maintains ammunition suppl
by timely orders to the ammunition bearers.

b. No. 1 (gunner.) No. 1 lays and fires the g:
and acts as section leader in the latter's absence
He is careful to coordinate his actions with No. 2

c. No. 2 (loader). No. 2 is responsible for com
plying with the fire commands insofar as the load
ing of the gun with the proper type of ammunitio!
is concerned. He coordinates his movements an

ns of the section are manned, he is the gunner

the second gun.

d. No. 3 (gunner’s assistant). No. 3 takes up a
position to the left of the gun for close-in defense.
When the situation requires, he may carry ammu-
nition from the vehicle to the gun. If both guns
are manned, he is the loader of the first gun.

e. No. 4 (gunner’s assistant). No. 4 directs the
ammunition bearers in the placement of their am-
munition. It is his duty to select the proper type
of ammunition, prepare it for firing and hand it
to No. 2. If both guns are manned, he is the loader
of the second gun.

f. Nos. 5, 6, 7, and 8 (ammunition bearers). At
the direction of the section leader, Nos. 5, 6, 7, and
8 carry ammunition from the vehicle or section
dump to the gun. Otherwise, they take up posi-
tions in defense of the gun — No. 5 to the left,
and Nos. 6, 7, and 8 to the right.

g. No. 9 (vehicle driver). No. 9 is responsible
for driver maintenance of his vehicle and for its
concealment and camouflage when halted.

j: at the gun with No. 1. In the event both

37. SUPPLEMENTARY GUN AND AMMUNI-
ION CARRIES. a. Using light machine gun
ipod. Although the light machine gun tripod is
ot normally part of the section equipment, it still

тау be used as a mount from which to fire the
gun. When it is so used it may be left attached
to the gun for carrying, or No. 1 may be required
to carry it. In either case, No. 1 can carry two
rounds of ammunition.

b. Two-man carry. Two men can carry the tul,
for short distances. The carry is facilitated by
taching two long wooden rods parallel to the tub;
in such a manner that the rods can be supporte:
on the shoulders of the carriers. Nos. 2 and ;
initially carry the tube, and Nos. 4 and 5 forn
the relief team. In this method, two addition;
men are free to carry ammunition.

с. Three-man carry. By attaching a cross ba;
and/or by the use of slings, the gun may be car
ried for short distances employing three men. Nos
2, 3, and 4 carry the tube, and No. 5 is a relie
member. The cross bar is affixed to the breech —
end, and the carriers carry either by hand or by
slings strapped over their shoulders. The Мг!
man carries the muzzle end in a sling which ma:
be held in the hand or strapped over the shoulder
This method allows one more man to carr)
ammunition.

d. Emergency carry. With either the light or
heavy machine gun tripods in use, Nos. 2, 3, 4,
and 5 may carry two rounds of ammunition fo:
short distances.

38. TO FORM THE SECTION. At the command |
FORM FOR CREW DRILL, the members oí
the section fall in at attention in a column of two
behind the section leader (fig. 18). To clarify thei
positions for crew drill the sergeant command: `
CALL OFF. Upon that command the section call:
off from left to right and from front to rear; for
example, the first man in the left file is No. 1, the
first man іп the right file is No. 2, the second |
man in the left file is No. 3, etc. |

Figure 18. 75-mm rifle section at FORM FOR
CREW DRILL,

39. TO POST THE SECTION. At the соттап
POSTS, all section members move forward a
double time to positions directly behind thei
equipment which is laid out in order (fig. 19) on
the drill ground.

Figure 19. 75-mm rifle section at POSTS,

40. ТО EXAMINE EQUIPMENT BEFORE
DRILL. a. At the command EXAMINE UM
MENT BEFORE DRILL, given while the men
are still at posts, individuals examine equipment in
the following manner:

(1) Section leader. (a) Determines that he has the
proper firing tables.

(b) Checks binoculars for broken parts and clean
enses.

(d) Checks compass to see that it is not broken
and that the needle is still on pivot.

(e) Checks sights.

(2) No. 1. (a) Checks traversing and elevating
handwheels and centers them.

(b) Checks clamping and jamming handles.

(3) No. 2. (a) Checks chamber and breech to de-
fermine that the chamber is clear and that the breech
mechanism is in firing condition.

(b) Checks for Allen wrenches in breech handle.

(4) Nos. 6, 7, and 8. (a) Check to see that all
ammunition is properly secured.

(b) Check to see that all straps are properly ad-
justed for carrying.

(d) No. 8 checks cleaning materials and rammer
staff,

(5) No. 2. Moves to the No. б, 7, and & positions,
checks type of ammunition being carried and its loca-
tion on the various ammunition bearers.

b. When all equipment has been thoroughly and
properly checked, the following commands are
given from rear to front:

(1) No. 8 reports CORRECT.

(2) No. 7 reports CORRECT.

(3) No. 6 reports AMMUNITION CORRECT.

(4) No. 2 reports CORRECT.

(5) No. 1 reports GUN AND AMMUNITION
CORRECT.

(6) The section leader reports ALL CORRECT,

41. TO SECURE EQUIPMENT. The section
leader gives the command SECURE EQUIP-
MENT and faces in the direction of march. No. 1
picks up the tripod and cradle and places himself
behind the section leader. No. 2 takes his position
at the right tube handle. No. 3 takes his position
at the left tube handle. No. 4 takes his position
at the breech handle. No. 5 takes his position zt
the trigger handle. Nos. 2, 3, 4, and 5 lift the
tube. Nos. 6, 7, and 8 sling ammunition and take
their positions in column behind the gun. The
section leader then signals and commands FOL-
LOW ME.

42. TO PLACE THE GUN IN ACTION. The
section leader designates, by pointing, the direction
of fire and the position upon which the gun is to
be mounted, and commands ACTION. He then
moves to the left front of the position designated
for mounting the gun, where he can observe the
target and control the firing of the gun. Moving

. to the left, No. 1 receives the sight from the sec-

tion leader. As No. 1 moves to the left, Nos. 2,
3, 4, and 5 place the tube on the tripod; No. 5
lowers the pintle latch lever, depresses the trigger,
and opens the breech; No. 2 removes the elevating
pin from its carrying recess, and when the gun has

peen correctly positioned, he places it through the
ront mounting bracket; No. 3 stamps the left leg
A into the ground; No. 2 stamps in the right
leg; Nos. 3 and 5 move to the left front of the
gun and take up security stations in defense of
the gun. In the meantime No. 1 has placed the
sight on the gun, locked it in place, and taken up
his firing position on the left of the gun. No. 2
takes up his position at the gun where he can
best service the piece. Sitting, kneeling on one or
two knees, or squatting, are all satisfactory posi-
tions. In the kneeling position, the knee nearest
the breech should be on the ground. No. 2 checks
the Боге for any obstructions, and reports CLEAR
to indicate to the gunner that the bore is clear.
Nos. 6, 7, and 8 bring up their pack loads of
ammunition and place them in a semicircle as
directed by No. 4. No. 8 places the rammer staff
and waste near No. 4 where he can easily reach it.
They then take up .security stations to the right
of the gun, No. 8 to the right front, No. 7 to the
right oblique, and No. 6 to the right flank. No. 9
is the vehicle driver and will not normally leave
his vehicle. The gun is now ready to fire. Upon
receiving the fire command, all elements of which
are repeated by No. 1, No. 4 draws the type of
P ammunition designated from its container and
passes it to No. 2. No. 2 inserts it in the chamber,
mates the preengraved rotating band with the
lands and grooves in the tube, and seats the round
firmly. He then closes the breech and taps the
gunner’s hand to indicate that the gun is ready
to fire. No. 1 lays the gun on the designated target,

takes the correct sight picture, places his hand
above the chamber, and waits for the tap from
No. 2 indicating that the gun is ready. On receipt
of the tap he rotates the safety and depresses the
trigger. After the round has been fired, No. 1 opens
the breech. No. 2 grabs the base of the expended
round with his left hand and throws it to the
rear, away from the gun position.

43. TO TAKE THE GUN OUT OF ACTION.
The section leader commands OUT OF ACTION.
At this command No. 2 clears the gun, closes the
breech, removes the elevating pin and replaces it
in the carrying recess. No. 1 removes the sight and
hands it to the section leader. Nos. 2, 3, 4, and 5
take their places beside the gun. No. 5 lifts the
pintle latch lever. Nos. 2, 3, 4, and 5 pick up the
tube and move to the rear. No. 1 swings the tripod
to his shoulders. Nos. 6, 7, and 8 pick up their
pack boards and fall in behind the tube. No. 8
also picks up the rammer staff and waste. The
section is again ready to move out under the direc-
tion of the section leader.

44. TO CHANGE NUMBERS AND DUTIES
DURING CREW DRILL. The section leader com-
mands FALL OUT ONE, TWO, etc. At this
command, No. 2 moves to the position of No. 1 and
calls out ONE. Each succeeding number will move
up one number and call out his new number. No.
1 moves to the position of No. 8. This rotation of
duties should be continued until each member
of the section is proficient in the duties of all eight

at the command is not given during the time
hat the tube is being carried, since it is difficult
to change over at that time.

= of the section. Caution must be observed

Section II. BATTERY DRILL

45. GENERAL. a. The object of battery drill is to
train the platoon to emplace guns in battery and
to apply indirect laying data promptly and ac-
curately.

b. The battery may consist of two or more guns.
The usual unit which executes battery fire is the
platoon.

с. The meanings of terms are given in para-

graph 120.

46. CONDUCT OF BATTERY DRILL. a. Gun
positions are indicated to the section leaders and
the guns emplaced pointing in the anticipated gen-
eral direction of fire.
b. All guns are laid parallel by any of the means
outlined in chapter 5.
с. After guns are properly laid for direction and
m deflections determined, a series of simulated
lissions are fired.
d. The following fire commands indicate how
Such an exercise may be conducted.
(1) BATTERY ADJUST
SMOKE
BASE DEFLECTION

NUMBER THREE ONE ROUND
ONE TWO SIX
FIRE |
(2) RIGHT ONE ZERO
ONE THREE EIGHT
FIRE
(3) HE
ONE THREE TWO
FIRE
(4 BATTERY RIGHT
ONE TWO NINE
FIRE
(5 NUMBER ONE: RIGHT SIX, ADD
FOUR
NUMBER TWO: RIGHT THREE
NUMBER FOUR: DROP TWO
ON NUMBER THREE CLOSE SIX
BATTERY
ONE ROUND
ONE TWO EIGHT
FIRE
(6) CEASE FIRING, END OF MISSION
ON NUMBER THREE OPEN SIX
RECORD NEW BASE DEFLECTION
e. Upon completion of this exercise, additiona
simulated firing should be conducted.
f. Initial drill of this type should emphasize pre-
cision. Speed will be attained through practice.

CHAPTER 4
MARKSMANSHIP

1 — А

Section І. GENERAL

47. PURPOSE. The purpose of this chapter is to
provide thorough and uniform methods of train-
ing individuals to deliver prompt and accurate di-
rect fire during combat on stationary ór moving
targets. Courses of instruction and rules and reg-
ulations for the conduct of marksmanship training
are included.

48. FUNDAMENTALS. To be capable of deliver-
ing prompt and accurate fire on stationary or mov-
ing targets, the soldier must be thoroughly trained
in the following fundamentals:
a. Correct sighting and aiming.
b. Correct positions.
€. Correct trigger manipulation.
1 d. Knowledge of range estimation.
е. Knowledge of speed estimation.
f. Knowledge of lead estimation.
g. Tracking exercises.

49. PRIOR TRAINING. The soldier should be
proficient in mechanical training and should be

thoroughly familiar with the operation and use o
the rifle accessories. |

Section II. PREPARATORY
EXERCISES

50. GENERAL. a. The purpose of preparatory
exercises is to teach the soldier the essentials of
marksmanship, and to develop fixed and correct
habits of marksmanship before he begins range
practice. A thorough, carefully supervised course
in preparatory exercises will conserve time and
ammunition during range practice and will incul-
cate in the individual automatic procedures to elim-
inate accidents.

b. Preparatory exercises are divided into eight
steps. These steps should be taught in the sequence
listed below:

(1) Sighting and aiming exercises.

(2) Position exercises.

(3) Trigger manipulation exercises.

(4) Range estimation exercises.

(5) Speed estimation exercises.

(6) Lead estimation exercises.

(7) Tracking exercises.

(8) Examination.

51. SIGHTING AND AIMING EXERCISES. a.
Sighting and Aiming with sight M85C. (Direct fire
up to 2,100 yards.) For description of sight M85C,
see paragraph 24.

(1) Aiming for range. Exercises should be con-

ercise should not involve tracking. The gunner
"s required to set the correct sight picture for every
100 yards of range (fig. 20).

(2) Aiming with leads. The distance by which a
target is led is measured from the point of aim,
and is equal to the distance the target will travel
between the time the projectile leaves the rifle and
the time its trajectory crosses the path of the
target. This distance is known as lead and varies
with the speed and path of the target. Five mils
is taken as the unit and is equal to one lead. Three

Fk on stationary 1000" “A” rifle targets. The

7676064
75-МЕ. AT. T39

l
-8---)---6
pre ry
b EAR CEN
ip S IUS

Figure 20. Correct range sight picture, tank 200 yards.

leads (15 mils) are used for each 10 mph that t
target is moving when the path of the target

at an angle of 45° or greater to the line of fir
When the path of the target is at an angle le;
than 45? to the line of fire, half this number ,
leads should be used. Exercises are conduct.
which require the gunner to set appropriate le;
markings on a caliber .22 — .30 “А” subcalib.
target (1000"). The target remains stationary :
a range of 200 yards, but is assumed to be movin
right or left at various angles and speeds (fig. 21)

76064
75- "t. AT. T39

Figure 21. Correct lead sight picture, tank right to left,
3 leads 200 yards.

(3) Aiming for range and leads. Range and lead
e combined automatically within the telescope
a series of horizontal lines extending to the
fant and left from center at 200-yard intervals. :
For targets requiring leads at ranges other than
those etched on the reticle, interpolation is neces-
sary: Select the appropriate range and lead points
on the telescope reticle and project them to an
imaginary point of intersection. This aiming point
is laid on the center of the target. Each gunner
is required to lay the rifle on the target (cal. .22 —
30 “A” subcaliber 1000") at various ranges and
leads. The target remains stationary with an

767606
75-Mt. AT. T39

Figure 22. Correct lead to sight picture, tank left to rignt,
3 leads, 500 yards.

assumed direction and speed being specified in ea,
case. Ranges and leads requiring interpolati,
should be included. At least one period of traini
will be devoted to use of the lighted reticle |
accustom all men to sighting and aiming with t}
telescope during the hours of limited visibili
(fig. 22).

b. Sighting and aiming with the M34 sight. Т}
M34 sight is used for direct fire for ranges ov.
2,100 yards.

(1) Aiming for range. (a) In using the indire
fire sight for direct fire, the sight must be fir.
adjusted for vertical parallelism. This is discusse
under boresighting, paragraph 59. When this oper:
tion has been performed, the M34 sight may b
used for direct fire. Estimate the range to th
target; set this range on the scale of the elevatio:
quadrant in mils (use firing table); and raise th
tube until the cross hair on the telescope is lai
on the center of the target (fig. 23).

Figure 23. M34, sight reticle and tank.
74

(b) Exercises should be conducted at any range

using а stationary 1000” “A” rifle target with
) assumed range over 2,100 yards.

(c) It is not to be construed that the M34 sight
cannot be used for ranges under 2,100 yards. A
direct fire sight (M85C) is furnished for this pur-
pose and can be used more rapidly since leads
and ranges are combined automatically on the tele-
scope reticle. However, the M34 sight may be used
if desired.

(2) Aiming with leads using M34 sight for direct
fire. (a) Leads may be set off on the sight using the
same rule as for direct fire given above. These
leads may be applied to the M34 sight by setting
the desired number of leads in mils on the scale
of the deflection quadrant.

(b) Exercises should be included in marksmanship
training which require the gunner to set various
Jeads on a stationary target with range, speed, and
direction of movement assumed.

(3) Aiming for range and leads. A combination of
exercises as given in (1)(b) and (2)(b) above
should be conducted until the gunner has reached
the desired efficiency in sighting at stationary
targets with assumed ranges, speeds, and direc-
tions. A 1000” “A” rifle target may be used -at
any range.

c. Sighting and aiming with M34 sight for in-
direct fire. For description of the sight, see para-
graph 25.

(1) Aiming for range. When firing indirect fire,
the range element of the fire command is given

in mils. This conversion is readily available in a
firing table. For example: the elevation in mil;
required for 3,000 yards is 177.3 mils. To aim anf
rifle for this range, set 100 mils on the elevation
scale. This is accomplished when the first gradua-
tion above “0” is opposite the index of the eleva-
tion scale. By turning the elevation micrometer
until 76 mils is opposite the index of the microm.
eter scale, we have set an elevation of 176 mils
on the elevation scale and micrometer. Since the
micrometer is graduated in 2-mil increments, we
must interpolate the half-way mark between 76
and 78 mils on the elevation micrometer scale
to obtain a reading of 77 mils. The .3 mil is
dropped since it is less than one-half mil. To com-
plete the operation and produce the desired eleva-
tion of the tube, manipulate the elevation hand-
wheel and cradle and raise the tube until the
bubble in the longitudinal level is centered.

(2) Aiming for direction. When aiming for direc-
tion using the indirect fire sight, the initial direc-
tion is given as a base deflection for each gun
when the battery is put in position to fire. There-
after, changes in direction are given as references
left or right so many mils from base deflection.
When the change is left, add the change in mils
to the base deflection; when the change is right,
subtract the change in mils from the base deflec-
tion. The keyword “LARS” (left, add: right, sub-
tract) will assist in remembering whether to add
or subtract changes in deflection. For example:
the command is BASE DEFLECTION, RIGHT
40. The gunner subtracts 40 mils from his base

deflection and sets this reading on the azimuth
cale and azimuth micrometer. He then moves

e tube until the vertical cross hair of the tele-
scope reticle is on the left edge of the aiming
stake. It is not necessary to check the cross level
bubble. However, when placing the gun in posi-
tion, every effort should be made to level the dial
and center the cross level bubble. Thereafter, un-
1655 the tube cants to an extreme angle, the cross
level bubble is not checked.

52. POSITIONS. Instruction in positions includes
positions for the gunner and assistant gunner when
firing at stationary or moving targets. For posi-
tions during firing, see paragraph 42.

53. TRIGGER MANIPULATION. The gunner
grasps the trigger handle with his right hand,
thumb on the trigger, forefinger or middle finger
rotating the trigger safety; and with a smooth
steady rearward pressure on the trigger, fires the
piece. Care must be taken not to throw the rifle '
off the target or aiming point while rotating the
trigger safety or depressing the trigger. The cor-
rect sight picture must be held while firing.

| RANGE ESTIMATION. Accurate range esti-

ation is essential to obtaining hits with a min-
imum expenditure of time and ammunition. Esti-
mation of the range to targets, stationary and
moving, should be stressed until the desired pro-
ficiency is attained. For methods of training in
range estimation see paragraph 79.

55. SPEED ESTIMATION. a. Speed estimatio,
is an essential phase of preliminary marksmansh;
training. The firer must base the number of leac
upon his estimation of the speed of the targe
Constant practice in estimating the speeds of moy
ing targets is the only method by which the i;
dividual can acquire accuracy in speed estimatio;
Training must include the use of many target
at various ranges, speeds, and directions of move
ment.

b. Exercises in speed estimation should be cor
ducted in the form of an examination with target
moving according to a prearranged plan. Initiall
the section is shown by demonstration the appea:
ance of different targets moving at announce
speeds and ranges. Each man is then require
to estimate the speed of targets moving at variou
ranges in various directions.

56. LEAD ESTIMATION EXERCISES. Exe
cises are conducted with targets moving at vario:
ranges, speeds and directions. Based upon observ:
tion of the target, the individual computes t!
necessary leads in accordance with the method :
lead determination as given in paragraph 85.

57. TRACKING EXERCISES. When the gunn
has become proficient in the previous steps |
marksmanship, training in tracking moving targe
should be conducted on 1000" ranges with pred
termined speeds and ranges. Training should |
continuous, progressing to vehicles, tanks, et
moving first at predetermined ranges and spee

and moving finally at undetermined ranges and
speeds. Sufficient exercises should be conducted to
bring the gunner to a high level of proficiency.

58. EXAMINATION. Before range practice is be-
gun each man should be examined to see that he
has attained the desired proficiency. The type of
examination need not be the same for all individ-
uals. An oral applicatory examination at the close
of each phase of marksmanship, followed by a
general review of all phases on the completion of
marksmanship training, should be satisfactory.

Section III. BORESIGHTING

59. BORESIGHTING. a. Sight M85C. To bore-
sight the rifle with this sight it is necessary to
make the axis of the bore (extended) intersect the
line of site at some distant point, preferably a
point beyond the range to any likely target. On
the muzzle end of the gun there are four notches
90° apart. If threads are stretched across alternate
notches, the intersection of the threads defines the
axis of the bore at the muzzle end. If the breech
Operating handle assembly is removed from the
breechblock, the fiing pin aperture defines the
axis of the bore at the breech end when the breech
Is closed. (The cut-off base of an empty shell case
Twith the primer punched out can be inserted into
_ the cone, and the primer aperture used in place
of the firing pin aperture.) By elevating and tra-
| Versing the piece, the axis of the bore can then
_ be aimed at the aiming point. To place the reticle

cross on the same aiming point it is necessary
to loosen the elevation and deflection worm lock-
ing nuts (fig. 24). When these are loose, the
elevation and deflection worms on the telescope
mount can be turned with a screw driver to adjust
the position of the reticle cross with respect to
the aiming point. When the reticle cross and the
axis of the bore are on the same aiming point, the
piece is boresighted.

b. Sight M34. (1) Adjustment of the elevation
quadrant. If the elevation quadrant is in adjustment,

| TELESCOPE CLAMPING LEVER
[DOVETAIL SLOT

MOUNTING BRACKE'
TELESCOPE HOLDER PRAES.

INSTRUMENT
LIGHT CLAMP AZIMUTH CLAMP NUT -

beam а Lat aliut mia la -Ж tS.

Figure 24. Sight bracket showing locking nuts and worms.

the tube will be elevated to the number of mils
jndicated on the elevation scale and micrometer
when the longitudinal bubble is leveled. To test
the adjustment, set the scale and micrometer of
the gunner’s quadrant to zero, place the quadrant
on the gun and by means of the elevating mech-
anism on the gun, level the bubble on the gunner’s .
quadrant. Level the longitudinal bubble on the
elevation quadrant of sight M34 by means of the
elevation micrometer knob on the sight. The eleva-
tion and micrometer scale should then read zero.
If they do not, they must be made to read zero
as follows: loosen the screw in each end of
the scale and shift the scale until it reads zero;
tighten the screws. Loosen the three small screws
in the end of the elevating knob and while holding
the knob to prevent it from moving, shift the
licrometer scale to read zero; tighten the screws.
Check the settings with the level bubble to make
sure that the elevation micrometer knob did not
turn when the screws were being tightened.
(2) Adjustment of cross level. If adjustment of the
cross level is necessary it must be made by ord-
nance personnel.

(3) Adjustment of deflection scale and micrometer.
(a) Aim the axis of the bore at an aiming point.

(b) Look through the telescope and, using the
azimuth worm knob, bring the vertical line of the
Teticle to bear exactly on the aiming point. The
azimuth scale and micrometer should then read

| Zero. If they do not, they must be made to read
Zero as follows: Loosen the four screws in the
damping ring and slip the scale until it reads

81
E

zero; tighten the screws. Loosen the large clamp- ,
ing nut in the end of the micrometer knob, and
while holding the knob to prevent it from turning,
slip the micrometer scale to read zero; tighten
the clamping nut. Check the readings and the
alinement on the target to see that the knob did
not turn while the clamping nut was being
tightened.

(4) Adjustment for vertical parallelism. If it is de-
sired to use the elbow telescope for direct fire, the
line of sight must be adjusted for vertical parallel-
ism. To make this adjustment, loosen the elevating
clamping nut and elevate or depress the telescope
until the cross hair of the reticle falls on the aim-
ing point.

Section IV. QUALIFICATION
COURSES

60. GENERAL. a. Personnel who are to fire for
qualification should have completed training in
the following subjects:

(1) Mechanical training. (a) Nomenclature, dis-
assembly and assembly.

(b) Care and cleaning.

(d) Stoppages and immediate action.

(e) Fire control instruments.

(f) Boresighting (with both direct and indirect
sight).

(2) Crew drill.

(3) Preliminary marksmanship. (a) Sighting and
aiming.

(b) Trigger manipulation.

(d) Fire commands.

Qualification courses for the 75-mm rifle con-
of the following:

(1) Course A—1000” subcaliber, mid-range sub-
aliber, and service firing. Course А is for use at
S, camps, and stations where range facilities
rmit the firing of service ammunition in accord-
nce with the provisions of AR 750-10.

(2) Course B — 1000" subcaliber and mid-range
u bealiber firing. Course B is for use where range
cilities prohibit the firing of service ammunition.
(3) Course C — 1000" subcaliber firing. Course C
s for use where range facilities include only indoor
anges or miniature outdoor ranges.

2 Instruction practice is not limited to the firing
ables found in paragraph 6le. Time, facilities, and
ammunition allowances will determine the amount
f firing.

d. The fundamentals emphasized in the quali-
cation courses are:

р Rapid and accurate delivery of the initial

E: round.
(3) Rapid determination of speed, lead, and

61. COURSE A. a. General. General instructio;
practice consists of firing tables I and III twic
and tables II and IV three times. Record practic,
consists of firing tables I, II, III, IV, and V ong
(see e below).
b. Equipment.
1— 75—mm rifle, complete with sight MSS
and mounted on MG tripod M1917A1.

Firing Point For Recoilless Rifle
5 I

ETTE

O+ Ow

FENCE OR ROPE

ENCLOSURE

Ay a ALTERNATE POSITION IF

i TOWER IS AVAILABLE
LEGEND: Ò GUNNER
О Loaner
X COACH (SCORING OFFICER FOR RECORD PRACTIC
& FEEDER ( WITH RED FLAG)
ô OFFIGER CONDUCTING FIRING

Figure 25. Range organization.

1 — Screw driver per rifle.

Boresighting equipment.

Stop watch.

Firing tables.

с. Conditions. (1) Organization of the range is
im accordance with the provisions of paragraph
69 and AR 750-10.

(2) Rifles are emplaced with tools nearby in
accordance with operational diagram (fig. 25).

to zero his rifle. Five rounds of caliber .30 carbine
pall ammunition are fired at 1000" target “A”
ile). Using an assumed range of 700 yards, the

Table I. 1000" subcaliber stationary target

"Rounds Time Target Score Remarks

ES. No limit .RifleA.....20 ^ Four 1000" “A”

(rifle) targets are
EL... No limit .Rifle A.....20 placed on a ma-
chine gun target

Rates ie No limit .Rifle A.....20 frame at least 12”
: apart laterally and
COME Nolimit .Rifle A.....20 6" vertically, form-

ing a rectangle.

Total: 80

Table II. 1000" subcaliber moving target

Speed Time

No. rounds Inches/ exposed, Lead 9mm Remarks
sec (sec) "C
e ICE S ТО AD Д: ОЗЕ 1002. DOR
РАР dede LASCIO 41527227 72: О ТОКЕ.
20 16:6: ЗІ е Tes IO Pto, К
Darcie AA ners АНЕ ssa ID ev 10....R to L
De semis А DAs redes 2I devise ASAD 10 L to R
2D bes РАЕН PAL Боос 2:59» ОККО) L
12 Total “60

(1) Target is 1000” “A” (rifle) target.

(2) Commands by officer in charge of firing.

(a) Preliminary commands:

LAY ON AIMING STAKE (in center of

target run).

ONE ROUND, SUBCALIBER, LOAD.
(All guns lay on aiming stake and load one

round.)

(b) Fire command:
MOVING TARGET
SUBCALIBER
LEFT (RIGHT) FRONT

TOP (CENTER or BOTTOM) TANK

SEVEN HUNDRED
ONE LEAD
FIRE

‘able III. Known distance, subcaliber stationary target

Maximum

Remarks
Score

rounds Range Target

105. ....All See below. т... 1...0: Targeting
allowance.

hd
7 5......200 Prone “Е” M-1917 25
complete.

285......300 Prone “F? M-1917 25 All firing on
1 this table

Г complete. К
is done
5......400 Kneeling “E” M-1917 25 with trac-
complete. er ammu-
nition,
Total: 75

Scoring: Targets will be scored by personnel in the pits at the 200,
10, and 400 yard lines. Scoring personnel in the pits should have
lephone communication with the firing point. If the facilities described
* are not available, a known distance rifle range with “E” targets
е substituted,

Table IV. Subcaliber moving target

Lead Speed ыы Remarks

ERES. uses 1 c 10 mph. ....... EEA L to R

^ Ыы... Ma ODN к a 2071 TENROS

EN OOA АО доора 205 Kan sie .L to R

0 CEPIT TICU Тор s «0 AOSS ..R to Е
Total: "80

cal with table II. Tracer ammunition is used in this table. When
used, scoring is accomplished by observation of strike of tracer
er. When a towed target is substituted, the target will be
td rather than scored by observation from the firing line,

Table V. Service firing, known distance

ounds Range Target x он
Ван 400 yds....55 gal. drum............20
‚г 800 yds 3’ x 5’ log barrier.......20
Total: 40

Jote. The first round fired at either range does not count for score,
r it is a Їйї or not. The gunner is credited with ten points for
first hit he receives after the first round fired. He ceases fire after
hit and receives five points for each unexpended round of the
al four rounds.

(3) Ammunition. Target practice ammunition
uld be used. Inert ammunition is an authorized

stitute.

COURSE B. a. Course B will consist of tables
I III, and IV.
. Instruction practice and record practice for

tables indicated will be fired as outlined in
se A.

‚ Equipment, conditions, and procedure will be
tlined in Course A.

COURSE C. a. Course C will consist of tables
nd II.

D. Instruction practice and record practice for
tables indicated will be fired as outlined in
Irse A (see sample score card in fig. 27).

» Equipment, conditions, and procedure will be
outlined in Course A.

£9

INDIVIDUAL SCORE CARD |
QUALIFICATION COURSE
75-mm RIFLE

(Name) (Grade) (Serial No.) (Organization)

Firing Phase

Ist 2nd 3rd
Instruc- | Instruc-| Instruc-
tion tion tion
Practice | Practice | Practice

Record
Practice

Scorer's
Initials

TABLE I
TABLE II
TABLE III
TABLE IV
TABLE V

TOTAL

QUALIFICATION

Certified Correct

Figure 27. Sample score card.

í 4. QUALIFICATION SCORES*. a. Course A.

БЕ рег nb dian cs eee tasa NR 260-335
est Class: Gunner's. 0, ees tere eid tis 240-259
end ClassGunner). os... sees oo 190-239
папа еайын. 189 or below
_ b. Course B.
Бере ЕЕ Лл Л: 230-295
Iste Glassy Gunner: о.о: 212-229
2nd Class Gunner ........ eee. 160-211
Arig tialified’s ооо 159 or below
c. Course C.
Epere ia o aala ide aene de ntes 125-140
Ist. Glass» Gunnera 3292 УА 110-124
And Glass. Günner о 80-109
inqualified ОССЕ ve set ro si ees 79 or below.

Section V. SAFETY PRECAUTIONS AND
PROCEDURE FOR FIRING

5. GENERAL. a. Because of the danger to per-
nnel, resulting from the back blast of recoilless
yeapons, extreme care must be exercised in all
hases of instruction. From the earliest stages of
raining this danger must be emphasized. Any crew
Till, position exercises, tracking exercises, or sub-
aliber firing must be conducted as though actual
ervice ammunition were being fired.

‘Organization commanders should, prior to range practice, assure
mmselves that the qualification scores agree with the latest published
ulations, and should make changes in this manual in pencil to agree
With such regulations.

EE-DANGER AREA

=-CAUTION AREA

Figure 28. Diagram showing danger area in rear of
75-mm rifle, M-20.

b. The danger zone (fig. 28) is triangular shaped,
extends approximately 75 feet to the rear of the
point of emplacement, and covers a space of 25
feet on either side of the axis of the emplaced
rifle at it widest point. No personnel should face
the weapon within 125 feet of the rear of its
breech because of danger of flying particles thrown
up by the blast action.

c. It is dangerous to operating personnel to fire
the weapon from closely confined spaces, such
as dugouts or foxholes, because of the concussion
from the backblast. The weapons can be fire
from semiconfined spaces, such as the rooms o
buildings, without danger, provided the room i:
large, with sufficient openings to allow rapid escapi
of the powder gases. Firing can be accomplishe
from any semiconfined space provided there is a:

` 92

opening directly behind the breech through which
he back blast can pass. Firing from rooms wherein
here is a wall too close to the breech will result
n damage to the wall and discomfort to the operat-
mg personnel even when there are sufficient out-
jets for the gases to escape.

'd. Most conventional type weapon emplacements
are unsuitable for this weapon. Any emplacement
wh ere there is an obstruction too near the breech
js unsuitable because the obstruction will tend
to deflect the concussion toward the operating
personnel. Most suitable types of emplacements
are those which leave the gun exposed, or semi-
exposed, with no obstruction behind the breech,
and provide for cover for the operating personnel
on either side of the gun. (For details of emplace-
ents see FM 5-15.)

. All firing is controlled by definite fire com-
ands.

f. During the initial phases of instruction firing,
e officer conducting firing may, at his discretion,
duce the speed of the target and the number of
founds fired in each run. The object of this proced-
(Ше is to increase confidence and place emphasis
9n manipulation and accuracy.

h. During instruction firing only, moving target
ng may be preceded by one or more dry runs.

"led by the unit commander, is responsible for —

(1) Assignment, coordination, and supervision of
the firing line to emphasize safe and smooth opera
tion of all firing. (

(2) Issuance of fire commands and general in.
structions to the firing line.

(3) Enforcement of safety precautions pre-
scribed in AR 750-10 and this manual.

(4) Organization of the range.

b. Company commander. The’ company com.
mander is responsible for the efficiency of the
marksmanship training in his organization and
for the conduct of its firing.

c. Scoring officers. (1) Scoring officers are de-
tailed to supervise record practice firing. Officers
for this duty will be detailed from organizations
other than the one firing. They will familiarize
themselves thoroughly with their duties and with
firing procedure prior to the date of record prac-
tice firing.
^ (2) Scoring officers will perform the following
specific duties:

(a) Check dimensions of the targets, aiming sil-
houettes, and scoring spaces.

(b) Inspect each target before firing to insure that
it contains no unpasted shot holes.

(d) See that firing is being conducted in accord
ance with the prescribed procedure.

(e) Check time of exposure on moving target rur:
and render a decision in the event of irregularities.

(f) Verify and render decisions on all misfires
nd malfunctions at the guns under his jurisdiction.
(g) Render a decision in the event of breakage

stoppage in any of the range apparatus.

(h) Score targets on each exercise fired and record
the score.

Р d. Coaches. During all preparatory training
practice a coach will be present at each gun to
instruct and assist the gunner. No coach will be
present at the gun for record firing. The specific
duties of the coach are as follows:

(1) Require each gunner and loader to observe
all pertinent individual and general safety precau-
tions, and insure compliance with instructions per-
taining to the service of the piece.

(2) See that the proper number of rounds is
present at the piece for each exercise.

(3) Supervise generally the work at the gun and
make sure that the commands are executed prop-
erly. Repeat orders and instructions where neces-
to insure correct understanding and timely
execution.

(4) Report all misfires, malfunctions, or dis-
сгерапсіеѕ to the officer conducting firing.

(5) Score the targets and critique the firing.

е. Loader. (1) The primary duty of the loader
S to serve the piece during all firing exercises.
During instruction practice he may also act as
assistant coach. During record firing he will not
©оасһ or instruct the gunner in any way.

(2) The specific duties of the loader are as
follows:

(a) Load the rifle in accordance with the com.
mands of the officer conducting firing.

(b) Tap the gunner and report “up” when thé
weapon is loaded and he is completely clear of th.
breech.

(d) Repeat all orders to unload, cease firing, and
clear gun.

(e) Announce to the gunner the number of rounds
to be fired on each exercise when required.

f. Feeder. (1) The feeder controls the movement
of personnel to and from the firing line and allows
no movement behind the line of guns except under
the direction of the officer conducting firing.

(2) The specific duties of the feeder are a:
follows:

(a) To allow no personnel to move to or from
the firing line except when all breeches are open and
personnel are standing free of the gun.

(b) After completion of firing by each order, to
send subsequent orders to the guns on command
of the officer conducting firing. |

(c) To raise a red flag at the end of the firing line
except when all breeches are open, all personnel
are clear of the guns, and instructions are receive
from the officer conducting firing.

(d) To permit no personnel to move behind the
guns while the red flag is raised.

67. ORGANIZATION. a. Organization of the fir
ing line is in accordance with figure 25.

— b. Duties of personnel are as outlined in para-
eraph 66.

(с. No personnel are allowed at any time to
enter the fenced or roped off enclosure*except those
actually required on the firing line.

d. No personnel may enter or leave the firing
line and no movement between guns will be al-
lowed when the red flag is raised.

e. Prior to any firing each gun will be carefully
checked by an officer to insure that it is in firing
condition.

68. INSTRUCTION PRACTICE FIRING. a.
General. (1) Before firing, the officer in charge of
firing gives a description of the range and an-
nounces specific instructions pertaining to firing
procedure.

(2) Guns are numbered from right to left.

(3) The coach, loader, and gunner take posi-
tions at the gun. The gunner tests the firing, elevat-
ing and traversing mechanisms; the loader secures
the necessary ammunition.

(4) When all guns are prepared for firing and
the safety regulations checked, the officer conduct-
ing firing gives the fire command.

(5) At the completion of an exercise the officer
conducting firing commands: CEASE FIRING.
"he loader rapidly unloads the gun, all personnel
Stand clear of the gun, and the loader then signals

b. Stationary target firing. An example of the

sequence of a fire command is as follows: FIRE
MISSION, SUBCALIBER, FRONT, TARGET,
SEVEN HUNDRED. When all guns have sig-
nalled “Ready,” the officer conducting firing com-
mands: FIRE. Each gunner fires as directed until
his ammunition is used up or until the command,

CEASE FIRING is given.

c. Moving target firing. An example of the se-
quence of a fire command is as follows: GUN ON
AIMING STAKE, LOAD. When all guns have
signalled “Ready,” a subsequent fire command is
given as follows: MOVING TARGET, SUB-
CALIBER, LEFT FRONT, TANK, SEVEN
_ HUNDRED, TWO LEADS, FIRE. When the
target has completed its run, the command CEASE
FIRING is given. The same type of sequence is
used for the return run.

d. Record practice firing. (1) The same proced-
ure as that. prescribed for instruction practice firing
will, except as noted below, be employed for record
firing.

(2) Each man will complete the prescribed in-
struction practice firing for the course specified
prior to record practice firing.

(3) As a rule, record practice firing will not
be executed on the same day that any portion of
instruction practice is fired. However, when the
time allotted is very limited, the unit commander
may authorize record practice firing on the same
day.

(4) Before firing any exercise for record, the
gunner wil be given a reasonable length of time

yo check the condition of his gun, sight, and am-
iunition.

(5) The gunner will be required {о boresight
r target his own weapon prior to any record

- 6) The target speed or allotted time will be
given each gunner prior to firing.

(7) In record practice firing, when a misfire,
stoppage, or malfunction occurs, the gunner or
loader will hold up his hand and call, “Stoppage.”
Thereafter, neither the loader nor gunner will
touch the gun until so instructed by the scoring
officer who will examine the gun.

(8) If a misfire, stoppage, or malfunction occurs
‘ough no fault of the gunner, the score will be
disregarded and the gunner permitted to refire the
exercise.

(9) Decisions to disregard scores or to authorize
réfiring of portions of the course rest with the
coring officer.

10) If a misfire or malfunction is manifestly
the fault of the gunner, he will not be permitted
refire the portion of the course affected.

9. SCORING AN INDIVIDUAL FOR QUALI-

fired by him will count as a part of the exercise.
c. The gunner who fires at the wrong target
ОГ scoring space will be given credit only for those

hits which strike the proper target or scorin,
space.

d. A hit will be scored for each bullet hole four
in a target or scoring space, except that no mo;
than the prescribed number of shots will |
counted. In moving target firing wherein a tani
is used, observation of tracer strike on the tar
will count as a hit. In field service firing, observ;
tion of strike on the target will count as a hi
'The target need not be marked.

e. For 1000" firing, the name of the gunner wil
be placed on each target before firing. Ехсер
under the supervision of the scoring officer, n
person will handle any target until it has bee
scored.

f. A bullet hole which touches the line of :
scoring space will be classed as a hit.

g. For moving target firing, ammunition no
fired during the time of exposure of the targe
will be forfeited.

h. Holes made by ricocheting bullets, rocks, o
other foreign matter will not be counted.

i Each individual entry for record practice wi!
be made on the score card in ink or indelible penc
and will be authenticated by the scoring officer
Erasures are not permitted. Alterations will |
made only by the scoring officer, and such alter:
tions will be authenticated by that officer.

100

1] CHAPTER 5
TECHNIQUE OF DIRECT FIRE

Section І. GENERAL

70. DEFINITIONS. The operation involved in the
application of effective fire on a target is called
"technique of fire." The operation involved in
pointing a gun for direction and elevation by direct-
ing the line of sighting on a target visible to the
gunner is called "direct laying." Since the primary
mission of this weapon is direct fire at point
targets, the technique of direct fire is particularly
important.

71. SCOPE. Direct laying involves a knowledge
of. the subjects listed below:

"a. Characteristics of fire.

Б. Range, speed, and lead determination.

с. Target designation.

а Fire control.

—e. Fire commands.
Т Range cards.
Section II. CHARACTERISTICS OF FIRE

72. TRAJECTORY. The trajectory is the imagi-
nary line traced by the projectile from the gun to

101

the point of impact. The 75-mm rifle M20 is classe,
as a flat trajectory weapon, but because of t|

action of the air resistance and the force of gravi

on the projectile the trajectory is actually a сигу
The angle of fall is greater than the angle of eleva]
tion and the projectile reaches its maximun
ordinate (highest point) closer to the point oj
impact than to the gun (fig. 29). A tangent ty
the trajectory at the point of impact is called thg
line of impact. The angle between the line oj
impact and the ground at the point of impact ij
called the angle of impact. |

GUN LEVEL: POINT
RANGE ——

Figure 29. Elements of trajectory.

102

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73. DISPERSION PATTERN. Factors such af
difference in weight and composition of propellant,
differences in weight of projectiles and varying
atmospheric conditions cause dispersion of the
points of impact of projectiles fired under other.
wise similar conditions. A number of rounds fired
at the same elevation and deflection form a definite
pattern in the impact area. This pattern is roughly
elliptical in shape with its longer axis along the
line of fire (fig. 30). In other words, the shots
are scattered more in range than in deflection.
The density of the shots is greater at the center
of the pattern than toward the edges.

74. RANGE PROBABLE ERROR. It has been
found through experiment that if enough shots at
the same elevation and deflection are fired, half
will fall beyond the center of impact and half will
fall short of it. In figure 30, the line AB has been
drawn through the center of impact, perpendicular
to the line of site. The line CD has been con-
structed parallel to AB so that the number of
shots between AB and CD is the same as the
number in the remainder of the right half of the
dispersion pattern. The area ABCD will therefore
contain 25 per cent of the shots fired. The length
(in the direction of fire) of the 25 per cent zone
represents one range probable error because this
error is exceeded as frequently as it is not ex-
ceeded. If lines are drawn parallel to AB at dis-
tances of one probable error from the center о!
impact, the small areas thus created will contain
percentages of total shots fired approximately a:

104

own in figure 30. Eight probable errors (four
either side of the center of impact) will cover
» dispersion pattern. The value in yards of a
ge probable error, which value varies directly
the range from the gun to the center of
is given in Firing Table 75-BB-1

ig from a direct fire position will be very
ted, in which case it becomes vitally important
arrive at the correct range determination at
earliest possible moment. Practice in determin-
ng ranges by most of the methods explained in
8 following paragraphs will usually improve

b. Estimating distance by eye.

с. Obtaining the range from other units.

105

d. Firing the gun.
e. Measuring the range on the ground.

78. TAKING RANGE FROM A MAP. The ac.
curacy of this method will depend on the skill oj
the person reading the map and the accuracy o;
the map itself. The distance gun-target is measure;
on the map and, by means of the map scale, the
measured distance is converted into yards of range

79. ESTIMATING DISTANCE BY EYE. a. Esti.
mating range by eye is the quickest method. The
degree of accuracy depends on the observer and
on his training and experience. In many cases it
will be the only possible means whereby range:
can be determined. Accuracy can be attained
through exercises which require the student to
observe a measured 100-yard marked distance from
various angles and from various ranges. After h:
has attained a mental picture of what 100 yards
looks like from these various angles and ranges,
he is required to estimate an unknown distance.
He does this by applying successively his mental
100-yard “yardstick” to the range to be estimated.
For ranges over 500 yards the observer should
pick out a point which is half way, estimate thy
distance to the half way point, and multiply tnl
answer by two.

b. Objects appear closer or farther away with
different conditions of light and terrain. The effec
of these conditions on the appearance of the 100-
yard unit of measure is, however, negligible
Whenever the appearance of objects is used as 4

106

basis for range estimation, the observer must make
allowance for the effects noted below:

(1) Objects seem nearer—

_ (a) When the object is in a bright light.

- (b) When the color of the object contrasts sharply
with the color of the background.

- (d) When looking from a height downward.

— (e) In the clear atmosphere of high altitudes.

- (f) When looking over a depression, most of which

- (2) Objects seem more distant when—

| (a) Looking over a depression all of which is
visible.
(b) There is poor light or fog.

80. OBTAINING RANGE FROM OTHER
UNITS. Often a unit being relieved from a com-
bat position will have range cards, along with other
information, to be turned over to the relieving
unit. Other units of the same organization may
have the desired information. This source of in-
formation is usually reliable, especially if the
other unit has tested it.

81. FIRING THE GUN. The gunner fires at the
estimated range and, by observation, he adjusts
until he brings fire to bear on the target. He then
reads the range from the sight reticle.

107

82. MEASURING THE RANGE ON THE
GROUND. This method presupposes that the
situation will permit the observer to traverse the
ground. If this situation exists, the observer may
pace off the range, or measure it with tape or
speedometer.

Section IV.
SPEED AND LEAD DETERMINATION

83. GENERAL. Speed and lead determination are
very closely allied since the observer cannot arrive
at the correct lead estimation without first having
correctly estimated the speed.

84. SPEED DETERMINATION. Constant prac-
tice in estimating speeds of vehicles is the only
method by which the squad can acquire accuracy in:
speed estimation. It is unlikely that the members
of the squad will have any instruments with which
to measure the speed of moving targets. Their
success in arriving at reasonably correct estimates
will be in direct proportion to the amount of their
training and experience.

85. LEAD DETERMINATION. a. The distance
by which a target is led is equal to the distance
the target will travel between the time the projectile
leaves the gun and the time its trajectory crosses
the path of the target. The telescope with which
this gun is equipped provides measurement of
angular leads. Leads, therefore, will vary with the

108

ot with range. А
"p. It has been found that the ballistic qualities
f this weapon are such that three angular leads
should be allowed for each 10 mph of speed that:
the target is moving perpendicular to the line of
sighting. The angle at which the target is moving
will alter the number of leads to be taken as follows:
for targets traveling at an angle of 45° or less to
he line of sighting, use half the leads determined
for the estimated speed; for targets traveling
directly toward or away from the gun, no lateral
leads are necessary.

V and direction of movement of the target, but

Section V. TARGET DESIGNATION

86. PRELIMINARY TRAINING. As a prelimi-

ary to practical work in target designation, the
members of the 75-mm rifle crew must have a
Knowledge of the military and topographical terms
employed in designating targets; for example, crest,
hill, draw, cut, ridge, cross-roads, right, left, flank,
| and column. They should also be instructed in the
meaning and use of such terms as horizontal,
yertical, above, below, rectangle, square, triangle,
nil, yard, and pace. Finally, a thorough course in
isual training and range estimation should be
iven. The crew member must be taught to use his
€yes and retain mental pictures of what he sees,

87. METHODS OF DESIGNATING TARGETS.
Vargets can be designated by—
Oral designation.

109

Firing the gun.

Laying the gun.
The choice of method will be dependent somewhat
on the expediency required by the situation.

88. ORAL DESIGNATION. a. General. By this
method the target designation element is given
orally; however, arm signals and pointing, where
applicable, take the place of or supplement the
spoken word. The essential parts of an oral designa-
tion are announced in the following sequence:

Direction.

Description of target.

Range.

b. Direction. Wherever practicable, the direction
should be given simply by pointing, using only such
words as may be necessary. 'Front" is understood
as the direction in which the muzzle points, and
directions varying therefrom by successive angles
of 45° are: designated as “right (left) front," “right
(left) flank," "right (left) rear," and "rear." The
clock system of indicating direction may also be
used. In this system the observer imagines himself
standing in the center of a clock dial. Front will
then be twelve o'clock ; rear, six o'clock; right flank,
3 o'clock; left flank, 9 o'clock; etc. (fig. 31). One of
the best methods of designating very obscure
targets is to use successive reference points. A
clearly distinguishable reference is first designated.
Rapid recognition of such references is facilitated
by previous indication of certain landmarks within
the sector of fire, together with an understanding

110

GRSERVER,

REAR

jure 31. Diagram of clock system of indicating direction.

the descriptive terms to be applied to designate
landmark. The gunner is then led step by step
the target by naming successive reference points
il his line of sighting is brought on the target.

Description of target. Usually a word or two
sufficient to describe the target; for example:
chine gun, tank, pillbox. If reference points are
luded in the order, the word “Target” E
descriptive words.

. Range. The range is announced by the com-
nd RANGE followed by a statement of the yard-
such as EIGHT HUNDRED. In the fire com-
nd the word RANGE is omitted and the range
announced simply as EIGHT HUNDRED.

111

89. FIRING THE GUN. Designating a target }
firing the gun is a quick, sure, апд. simple metho
however, its use may prematurely disclose the gu,
position. The person designating the target actual],
fires the gun.

90. LAYING THE GUN. Laying the gun on.
target is another quick, sure, and simple metho
and does not prematurely give away the gun posi
tion. The person designating the target may actually
lay the gun himself to give the gunner his direction,
He completes the designation orally.

Section VI. FIRE CONTROL

91. GENERAL. a. Fire control implies the ability
of the leader to open fire at the instant he desires]
adjust the fire of his gun or guns upon the target,
shift it from» one target to another, regulate it;
rate, and cease fire at will. He must be able to do
all of these things promptly if the fire is to b:
effective. Lack of proper fire control results in
loss of surprise effect, premature disclosure 0!
position, application of fire on unimportant targets,
loss of time in securing adjustment, and wastag
of ammunition.

b. Fire control is founded primarily on thorough
discipline and technical training. There must bí
sufficient flexibility to provide for adequate decern:
tralization in order to compensate for the difficulties
encountered in firing guns from widely separate!
positions.

112

2 CHAIN OF FIRE CONTROL. The commander
onsible for the employment of the guns issues
orders relative to their use direct to the platoon
er. The platoon leader in turn gives fire com-
nds to his section leaders, and they in turn
municate their own commands to their gunners.
lecause of such factors as noise, semi-isolation of

ng compartments, limited vision, and fleeting
ortunity, fire control must be based on simple
hods to insure effective execution and the
agement of new and unexpected targets which
ear after the unit becomes engaged.

93. ADJUSTMENT OF FIRE. Normally for
s less than 1,000 yards, direct readings for
deflection, and estimated range corrections neces-
sary to bring the burst to the target will be

|! supervision of the squad leader, make his
m corrections and apply them to the weapon
without command. The squad leader will issue
Subsequent commands, when, in his estimation,
speed or effectiveness of.fire can be enhanced by
) doing. For ranges in excess of 1,000 yards
е squad leader issues subsequent commands
Sing the bracketing method of adjustment for
nge, and direct reading for deflection, unless his
owledge of the terrain indicates that the method
itlined for a range of less than 1,000 yards will
more expeditiously place fire on the target.

94 OVERHEAD FIRE. a. Overhead fire is fire
lelivered over the heads of friendly troops. The

113

75-mm rifle M20 is capable of delivering this ty,
of fire provided it is clamped and in a stabi
stationary position.

b. Overhead fire must pass a safe, carefully deter
mined distance above the friendly troops ove,
whose heads it is to be delivered; that is, th,
minimum clearance or safety angle must |,
_accurately established. The minimum clearance fo,
ranges up to 1,000 yards is determined as follow;
(fig. 32):

Gunner's Rule

(1) Lay the gun on the target with the correc
sight setting to hit the target.

(2) Without disturbing the lay of the piece, sigh:
down the reticle scale to the 1,200-yard graduatio:
and fix the point where the line of sighting strike:
the ground. If friendly troops are at ог. beyon¢
this point, it is unsafe to fire. Overhead fire can be
delivered until friendly troops reach this point.

Figure 32. Application of gunner's rule.

114

"The above method will insure ample troop
rance at all ranges up to 1,000 yards. It will
nsure that troops will be far enough from the
st area to avoid shell fragments. Where a
ere accurate determination for closer support is
sired, consult paragraph 165.

1 For determination of safety factors for ranges
vr 1,000 yards, computation of mask and troop
garances must be made by the method described
paragraph 157 or by use of table VII.

Section VII. FIRE COMMANDS

-ENERAL. a. Fire commands are orders which
ey all the information necessary for the com-
ement, conduct, suspension and cessation of
and activities incident thereto.

Fire commands must be given clearly, forcibly,
a speed which may be received and applied
out confusion. Much time is lost when a crew
Iber has to ask for a repetition of part of the
nand. The use of standard commands elimi-
s misunderstanding.

TYPES. Direct fire commands are of two
5: initial fire commands and subsequent fire

NITIAL FIRE COMMANDS. Initial fire com-
ds for direct laying of the weapon must contain,

Where applicable, the elements listed below:
а The alert.
Type of ammunition.

115

Fuze.

. Direction.

Target description.
Range.

. Leads.

. Command to open fire.

rom о aa

98. ELEMENTS. a. The alert. The alert is alw;
the first element of the initial fire command.
consists of the command FIRE MISSION in |
case of a stationary target, or the command MOVIY
TARGET in the case of a moving target. The ak
puts the gun crew in readiness to execute a f
command with the least practicable delay.
b. Types of ammunition. Ammunition is des;

nated in the fire command as—

HE (High explosive)

HEAT (High explosive, antitank)

SMOKE (Smoke)

TP (Target practice)

INERT
This element is announced immediately after th
alert. As soon as it is announced, No. four wit!

draws the proper type of ammunition from |

individual container and prepares it for loading i
the piece.

c. Fuze. The high explosive and target ргасії
rounds have fuzes which may be set for superqui(
(SQ) or delay action. The rounds are original!
packed so that the fuzes are set for superqui
action. To obtain delayed action it is necessary !

116

city DELAY in the fire command. If this
ment is left out of the command the projectile
be fired with the fuze set for superquick action.
(T, SMOKE, and INERT rounds have no fuze
ags. When using any of these types of ammu-
n, it is not necessary to mention the fuze
nent in the fire command.

1. Direction. Direction is generally given orally,

y pointing, or by a combination of these two
ods. It is sometimes pointed out, in connection
h target designation, by laying or firing the
Target description. A target should be
ribed as quickly and simply as is consistent
1 clarity. Where the target is obscure, it may
necessary to lead the gunner to the target by
ms of successive reference points.

Range. Range in yards, having been estimated

Leads. This element has application only in
case of moving targets. Leads are announced in
bers of five mil angular leads, as: THREE

Command to open fire. This element is given
FIRE, or in the event a short delay becomes

er time by the command FIRE.

EXAMPLES OF INITIAL FIRE COM-
NDS. a. (1) FIRE MISSION.

117

(4) MACHINE GUN.

(5) SIX FIVE ZERO,

(6) FIRE.

b. (1) FIRE MISSION.

(2) HE.

(3) DELAY.

(4) LEFT FRONT.
‚ (8 REFERENCE: HEDGE; RIGHT CO}
NER OF HEDGE, PINE TREE; BASE 0;
PINE TREE, TARGET, MACHINE GUN.

(6) EIGHT HUNDRED,

(7) 3 ROUNDS, FIRE.

c. (1) MOVING TARGET.

(2) HEAT.

(3) TWELVE O'CLOCK.

(4) TANK.

(5) SEVEN HUNDRED.

(6) THREE LEADS.

(7) FIRE.

100. NUMBERS. Numbers are announced as illu
trated below:

10 One zero.

25 'Two five.

300 Three hundred.
1400 One four hundred.
6000 Six thousand.
3925 "Three nine two five.
4050 Four zero five zero.

118

01. SUBSEQUENT FIRE COMMANDS. a. Sub-
sequent fire commands contain only such data as
re to be changed, except that the command for
range and the command FIRE must be repeated
sach time. Corrections or changes in range are
announced as ADD FIVE ZERO or DROP ONE
ZERO. Changes iņ deflection are announced as
ИСНТ TWO FIVE or LEFT ONE ZERO.
hanges in leads are announced as ONE MORE or
)NE LESS.

b. In order to correct an error in the fire com-
запа, the person giving the command calls out
ORRECTION, and immediately thereafter issues
he corrected version.

Section VIII. RANGE CARDS

02. RANGE CARDS. a. A range card (fig. 33)
'a diagrammatic or panoramic sketch showing the
sition of the gun, magnetic north, and ranges
nd azimuths to prominent terrain features and
robable targets. By reference to ranges to nearby
bjects, it enables the gun crew to determine
uickly and accurately the range to any target in
he sector. The squad leader also can lay the gun
or night firing on predetermined target positions,
y using the tripod dial or aiming stake. If the
lembers of the gun crew become casualties, the
ange card permits the replacement crew to deliver
fective fire on likely targets.

b. Range cards may be constructed as follows:
(1) Place a dot in the approximate center of a

119

Figure 33. Range card. (

piece of blank paper to represent the position of
the gun.

(2) Draw a straight line through the dot to
represent magnetic north, and label the line.

(3) Determine the range and measure the azi-

120

in mils to prominent terrain features to be
wn on the card.

{) Using a protractor and a convenient scale,
in the terrain features, labeling each.

3) Draw straight lines from the gun position
je terrain features and label each line with rànge
ad azimuth.

Section IX. DIRECT LAYING ON
LANDSCAPE TARGETS, 1000”

"SCOPE AND IMPORTANCE. a. Upon satis-
ory completion of the qualification course, the
ler may practice what he has learned by firing
andscape targets.

he advantages of landscape target firing are—
) It permits close supervision of all members
he firing unit.

2) It clearly and quickly demonstrates the
lication and effect of fire.

8) It can be conducted indoors when lack of
lities or weather conditions make this desirable.
4) It emphasizes target designation and fire
trol,

- DESCRIPTION. A landscape target is a
Oramic picture of a landscape. It is so drawn
t all or nearly all of the salient features are
ognizable at a distance of 1000 inches. The
ndard target is the Series A target of five sheets
black and white.

121

105. PREPARATION OF TARGETS. a. Moy,
ing. The sheets are mounted on frames made ,
by 2 inch lumber. The frames are 24 by 60 inc
and are covered with target cloth tacked to y
edges.

b. Range indicators. To permit proper designat,
of targets, assumed ranges must be used on 1а
scape targets. Small cards with appropriate nu;
bers representing yards of range are tacked alo;
one or both edges of a series of panels (fig. 3
The gunner zeros his rifle at a given range, a
must be cautioned that the range announced ;
any target designation is for the sole purpose,
designating the target; the sight setting necessa
to zero rifles must not be changed.

c. Direction cards. In order to provide the dire
tion element in oral target designation, small сагі
marked "front," “right front," “left front," “rig
flank," “left flank" are tacked above the appropria:
panels of the landscape series.

d. Scoring devices. (1) Scoring the exercise teni
to create competition between individuals or se
tions and enables the instructor to grade the
relative proficiency. For a point target, а scorir,
device conforming in size to the 50 percent and 7
percent shot groups can be made from wire, cell
loid, plywood, or similar material (fig. 35). T
scoring space can be outlined on the target
pencil before the target is shown to the sectio
leaders. This procedure prevents section leader
from misunderstanding the limits of the designat
target. Upon completion of firing, the entire sectio
is shown the target and the results of the firing.

122

123

‘s40}DIIpUt UONIIAID PUD 26uD4 YIN 12640} advISpUnT “PE 24901]

no
NT

: Figure 35. Scoring device 1000" range.

(2) Although shot groups take the form of a ver-
tical ellipse, the 50 percent and 75 percent zones should
be shown by the devices as rectangles. This is for
convenience in their preparation. At 1,000 inches the
50 percent zone is a rectangle 114 inches high by 1
inch wide. The 75 percent zone is a rectangle 21 |
inches high by 2 inches wide. The target is at the
center of the inner rectangle or 50 percent zone.

124

06. ZEROING OF RIFLES. Rifles are zeroed in
е same manner as outlined in paragraph 614,
sing an assumed range of 700 yards. At a distance
1,000 inches, changes of one mil elevation and
indage, respectively, will move the strike of the
ullet 1 inch in the desired direction.

97. FIRING PROCEDURE. The following se-
fence is used in conducting firing exercises:

a. All members of the section except the section
ader face to the rear.

b. The instructor takes the section leader to the
anels and points out the target to him. They
turn to the firing line, and the section leader
akes charge of the section and orders the gunner
d assistant gunner to resume their firing posi-

c. The section leader designates the target orally.
leference to panels to indicate direction should
ot be allowed in the designation. The section
ader completes his fire command with the com-
рапа, FIRE. Each gunner is allowed 10 rounds.

d. When the gunner has completed firing, the
ection leader commands: CEASE FIRING,
SLEAR RIFLE. He checks to see that this is
one. The target is then examined and scored.
|е. The instructor holds a short critique after
ach exercise.

f. For section competition, each member of the
ection is given a target; his score is computed and
ded to the score of other members of the squad.
Zombined individual scores indicate the score for
he section.

125

108. SCORING. The sum of the value of the hit
within the two zones is the score for the exercise
For convenience ‘of scoring and comparison, 100 ix
fixed as the maximum score. Any method of scor.
ing and of distribution of ammunition among mem.
bers of the section may be used. For example:

a. Number of rounds fired, 50. E
b. Value of each hit in 50 percent zone, 2.

c. Value of each hit in the area of the 75 percent
zone outside the 50 percent zone, 1.

109. EXERCISES. a. Number 1. (1) Purpose. To
teach target designation and to show the effect of
concentrated fire.

(2) Method. The platoon (section) leader directs
the fire of his platoon (section) at a point E"
indicated to him by the instructor.

b. Number 2. (1) Purpose. To teach Ee
designation and the division of the platoon (section)
fire between two points.

(2) Method. 'The instructor indicates two point
targets to the platoon (section) leader, giving the
nature of each. The platoon (section) leader applies
the fire of his platoon (section) on the two targets
in proportions indicated by the nature of each. The
scoring will be as for concentrated fire on each
target, the two scores being combined in total
for the score of the exercise.

c. Number 3. (1) Purpose. To teach target
designation and fire control in diverting part of the
fire of the platoon (or section with 2 guns in action)
to a suddenly appearing target.

126

2) Method. The instructor indicates a target to
platoon (section) leader. The platoon (section)
er applies the fire of one or more guns to this
et. After firing has commenced, the instructor
cates and gives the mature of a point target
he flank. He then directs the platoon (section)
er to shift one or more guns from the first to
> second target. The method of scoring is to
] the value of hits on both targets.

Section X. TRANSITION FIRING

PURPOSE AND SCOPE. This phase of train-
gives the individual gunner practice in search-
areas, estimating ranges, and firing rapidly and
irately. It emphasizes the necessity for con-
ed application of the principles stressed in
jer marksmanship training, and prepares him
field firing exercises which follow later.

- RANGES, PERSONNEL, AND PROCE-
RE. a. Ranges. The ranges are constructed to
vide targets as outlined in the firing table
уу. For protection of the pit detail, individual
n pits of the foxhole type should be used. To
trol the raising and lowering of targets, com-
lication between the firing points and pits is
ary. Targets are fastened to poles of suffi-
it length to permit exposure of the target from
pit without endangering the personnel in the
. The number of lanes constructed will depend
n the number of persons to fire.

‚ Personnel One officer is required at each

127

firing point to control the firing. Pit details w
consist of one or two men per target, with
telephone orderly at the firing point to transn,
Scores and orders for control of targets.

c. Procedure. After the command LOAD, t
officer in charge of firing gives the signal for t}
raising of targets. Unless hit, all targets гета;
up until the signal to withdraw them is give,
When all targets are withdrawn the target operat;
scores the targets and reports the score to t|
firing line. A coach at each firing point record
the score. Since a hit is indicated by the lowerin
of the target, no extra credit is given for more tha
one hit on a target. However, if two targets ar
hit by one bullet, both targets are scored.

112. FIRING TABLE. Firing will be conducte
in accordance with table VI.

Table VI. Firing Table

No. of Maximum
rounds Type target Range score
Ker Prone "F" M- unknown (0—200 5
1917 complete. yards)
З Prone “Е” M- unknown (0-300 5
1917 complete. yards)
dev qe Kneeling “E” unknown (300- 5
M-1917 com- 500 yards)
plete.
dimus. Kneeling “E” unknown (300— 5
M-1917 com- 500 yards)
plete. 20
Score for rounds not fired— 8
Possible score 28

128

a. Carbine tracer ammunition will be used.
— b. Time allowance; 3 minutes for entire table.
с. Gunner will be allowed 3 rounds to hit each
arget. If he does not get a hit in 3 rounds, he
proceeds to the next target. He will be scored 5
points for each target hit and will be given a credit
of one point for each round not fired per target,
providing the target is hit. No credit will be given
for rounds not expended per target if the target
js not hit. It is not necessary that all targets be
hit to receive credit for unexpended rounds on
targets that were hit with less than 3 rounds.

d. Target scoring will be done by operators in

е. Fifteen points is a satisfactory score for this
exercise.

Section XI. FIELD FIRING

13. PURPOSE AND SCOPE. The purpose of
held firing is to demonstrate individual and crew
proficiency in all phases of combat for the section
a id platoon. The unit is conducted through a
series of exercises which, as nearly as possible,
simulate battlefield conditions. The situation for
each exercise will be given by the instructor who
will act as umpire. The tactical commanders will
lirect and control their units in the actions
required. At the completion of each exercise, a
ritique will be held by the umpire.

14. EXERCISES. The terrain should be varied for
ch exercise, if possible, so that the unit will be

129

presented with a new situation for each exercise.
The following exercises are given as guides for
the preparation of such training.

a. No. 1 (direct fire). (1) Purpose. (a) For the
section leaders. Practice in control of their units in
order to engage properly various types of targets.

(b) For the members of the section. Application of
the factors which govern the selection of positions,
the use of individual cover and concealment am-
munition supply, and technique of fire.

(2) Unit. One section.

(3) Situation. The section is located in an assembly
area and is issued ammunition. The section leader
is given pertinent portions of an operation order,
to include position areas, target areas and sectors
of fire, and the location of friendly troops.

(4) Method. (a) The section leader selects his route
of approach, his gun position, and issues the neces-
sary orders to place the gun in position. When a
target is indicated, the section leader issues his
fire command, opens fire, and adjusts his fire. Fire
for effect is not a part of these exercises. As soon
as the fire has been adjusted, the duties of the
crew are rotated and a new target is designated.
The section leader must be prepared at any time
to displace forward, move to an alternate position,
or withdraw to a covered area. Selection of the
proper type of ammunition will be the responsibility
of the section leader.

(b) Some possible types of targets are—

1. Camouflaged cave type fortification with
natural camouflage. Cave opening to be
2 feet by 1 foot. Range 400-600 yards.

130

2. Mock tank or tank chassis. Range 600-800
yards.

3. Camouflaged log and earth pill- “box.
Range 800-1000 yards.

4. Pill box requiring section leader to smoke
the apertures. Range 400-500 yards.

b. No. 2 (indirect бге). (1) Purpose. (a) For the
aders. Reconnaissance and selection of positions,
putes of approach, observation posts, and control
f units.

(b) For the members of the unit. Same as exercise
ml.

(2) Unit.:75-mm rifle platoon.

(3) Situation. The unit is located in an assembly
ea and is issued ammunition. The section leader
given pertinent portions of an operation order,
include position areas, target areas, sectors of
е, and the location of friendly troops.

(4) Method. (a) The unit leader proceeds in the
me manner as that outlined in exercise No. 1; how-
rer, the situation should be presented so that
direct fire is indicated.

(b) The targets selected for this exercise should be
"such a nature that point target or limited area
e is clearly indicated.

. AMMUNITION. The exercises are designed
service ammunition; however, where range
bilities are limited, subcaliber ammunition may be
ed. Where subcaliber ammunition is used, the
Ction leader should be required to specify what
е of ammunition he would use were he firing

131

service ammunition. Also when subcaliber ammunj,
tion is used, the ranges of targets suggested (
paragraph 114a (4) (b) must be modified to les;
than 500 yards in order to observe the tracer strike.

116. CRITIQUE. At the completion of each exercise
the instructor should conduct a critique covering
the following points (care should be taken by the
officer conducting the critique to avoid confusing
effectiveness of fire with over-all unit performance):
Reconnaissance.

. Actions and orders of unit leaders.
Suitability of observation posts.

. Suitability of firing positions.
Suitability of alternate positions.
Use of cover and concealment.

g. Technique of fire.

h. Ammunition resupply plans.

i. Proper employment of types of ammunition.

mean op

132

CHAPTER 6
TECHNIQUE OF INDIRECT FIRE

Section I. GENERAL

117. PURPOSE AND SCOPE. Although the 75-

im rifle was designed primarily as a direct fire
eapon and will normally function in this role,
asions may arise which indicate the desirability
using the weapon in partial or complete defilade.
his chapter discusses the means by which such
e is effected. For more detailed description of
is subject matter see FM 6-40.

8. ORGANIZATION FOR INDIRECT FIRE.
xcept in position defilade firing, in which case the
server issues commands direct to the gunners,
ganization for indirect fire normally consists ofÍ—
a. An observer who sends back corrections in
rds to the battery. The observer is usually the
atoon leader or platoon sergeant, although any-
e trained in observation methods may act in
is capacity.

. A fire direction center which translates the
erver's corrections into fire commands and
sues them to the gunners. The fire direction
nter is usually made up of one or both section
aders and a radio or telephone operator.

133

Section II. COMPUTATION OF INITIAL DATA

119. PREPARATION OF DATA. Normally ud
observer designates the location of the target by
one of the means outlined in paragraph 132. Th.
fire direction center then prepares the initial data for
laying the guns. However, at times it may be neces.
sary for the observer to prepare his initial data,
When initial data are determined by the observer,
he must send them to the gun position in the
form of fire commands (see par. 155).

120. TERMINOLOGY. The definitions, abbrevia-
tions, and terms listed below are used in the
preparation of firing data.

a. Direct laying. The piece is laid by sighting
on the target.

b. Indirect laying. The piece is laid by sighting
on a point other than the target.

c. Firing angle (A). The clockwise horizontal
angle from the target to the aiming point (see fig.
36).

d. Deflection. The setting of the sight which
corresponds to the firing angle. An increase of
deflection moves the plane of fire to the left, a
decrease moves it to the right.

e. Measured angle (M). The horizontal angid
(vertex at the observation post) from the target
to an aiming point, base point, or other points
(fig. 36).

f. Target offset (T). The horizontal angle (vertex
at the target) between the piece and the observa-
tion post (fig. 36).

134

LU PAG
(

С AIMING. POINT

g. Aiming point offset (P). The horizontal angle
(vertex at the aiming point) between the piece
and the observation post (fig. 36).

h. Range (R). Distance in thousands of yards
from G to T.

i. Observed range (r). Distance in thousands of
yards from O to T.

j. Base deflection (BD). The deflection on the
sight when the gun tube is directed at the base
point and the line of sighting is directed at the
aiming point.

k. Base point (BP). A well-defined point in the
target area used as a point of reference from which
range and direction adjustments of artillery fire are
made. The location of the base point relative to
the weapons is known.

121. OBSERVER PREPARATION OF INITIAL
DATA. When the observer is required to prepare
the initial data (par. 119) the methods discussed in
the succeeding paragraphs may be employed.

122. COMPUTING DIRECTION. a. Hasty
method. When the observer selects an OP on or
near the line GT, he can direct the gunner to lay
on the OP by the following command: AIMING
POINT, OP, DEFLECTION ZERO, LAY ON
ME. When this operation has been completed,
the gun will be pointed in the general direction of
fire. )

b. Alidade method (fig. 37). The observer sights
on the gun with an alidade consisting of a pencil

136

-— B.

О
ALIDADE HIEN

ү:

ure 37. Alidade method of determining initial direction.

a straight edge. Without altering the position
e alidade, he measures the deviation (A) be-
еп the direction to the target and the direction
which the alidade points. He multiplies this
lation by the deflection correction factor r/R
btain the approximate value of angle B. He then
mands, AIMING POINT, OP; DEFLEC-
N RIGHT (LEFT)————; LAY ON ME.
Parallel line method. The observer estimates
shortest distance from the observation post
he line GT. He selects an object on the ground

137

to the front, on the same side of the line GT anq
at the same distance from this line as he is locate,
With a compass he determines the magnetic azi
muth of the selected object. This is the azimuth
of the line GT.

d. Rapid plotting method. A diagram may b.
drawn to scale, either on a sheet of paper or on а
map or overlay. From this diagram range anq
deflection may be read directly (fig. 38).

e. Compass and mil method. The compass and
mil method is used only when the angle T is les;

vA STEPS
4 I.MEASURE AZIMUTH O TO T
/ T | 2.MEASURE OR COMPUTE
/ DISTANCE O TO T
/ 3.MEASURE OR ESTIMATE
/ DISTANCE O TO G
А 4MEASURE L TOG
ie id 5.PLOT TO SCALE
/ 6.MEASURE “Т AND DISTANCE
GT
7.AZIMUTH б T EQUALS
AZIMUTH ОТ LESS VT

Figure 38. Rapid plotting diagram.

138

than 400 mils. The observer at the observation
post proceeds as follows:

- (1) Reads the azimuth of the line OT.

(2) Estimates the distance OT and at the same
time estimates the shortest distance from his posi-
tion to the line GT.

(3) Using the mil formula, he finds the angle T
and adds or subtracts it from the azimuth OT. If
the gun is on the left of the observer, he adds; if
the gun is on the right, he subtracts. The result
is the azimuth on which the gun should be laid.
Note. A convenient method for teaching observers to know

quickly whether angle T should be added or subtracted is to
se the word "GLARS" (gun left, add; right, subtract).

4 xample (gun right of observer) :
Azimuth OT ..... Ж РИИ РУКУУ A nite 1,800 mils.

Range ОША ite ch tree аз дис vetet ere IET d E 1,500 yards.
Shortést distance from O to line GT............ 300 yards.
.300

Is = 200 mils = angle T

Determine the azimuth of the line GT by subtracting 200
mils from 1800 mils.
The azimuth GT is 1600 mils.

f. M-10 plotting board. Direction, range, and
angle of site can all be determined using the M-10
lotting board. (For operation see paragraph 28
and FM 23-55.)

23. COMPUTING ANGLE OF SITE. When
pproximate initial firing data are used, the angle
f site may be estimated, or may be assumed to
e zero. However, when more accurate computation
5 desired, the observer may employ a contoured

139

map, an M-10 plotting board, or may compute it
by the use of an instrument, such as the aiming
circle and application of the mil relation formula,
In this latter method, the observer computes the
difference in elevation between the OP and the
gun, the OP and the target, and thus between the
gun and target. With this difference in elevation
he can find the angle of site of the line GT.

124. ELEVATION. (a) The range GT is deter-
mined from maps, by estimation, from friendly
troops, by rapid plotting, or from the M-10 plotting
board. The angle of elevation for this range is
found in the firing tables.

b. The angle of site and the elevation for the
range are added together algebraically and the
resulting quantity is known as the quadrant eleva-
tion. The quadrant elevation is placed on the sight
or the gunner's quadrant.

Section III. GENERAL PRINCIPALS OF
CONDUCT OF FIRE

125. GENERAL. This section is concerned with the
computation of factors, initial fire requests, and
general principles of observer conduct of fire. The
fundamental principle underlying observer conduct
of an adjustment is that all bursts should remain on
or near the OT line. For this purpose two proce-
dures are employed. These are the range-bracketing
and the deflection-bracketing procedures, each of
which will be discussed in later sections of this
chapter.

140

126. SENSINGS. One positive sensing is sufficient
to establish a limit of a bracket. Sensing must be
made promptly, except when it is necessary to
take advantage of drifting smoke. Sensing must be
based on what the observer sees while it is before
his eyes, not on what he recollects. Except for
terrain sensings, range or deflection sensings on
bursts wide of the target should be made with
caution. When sensings are made on drifting smoke
or on shadows, the direction of the wind and the
position of the sun must be considered.

127. BRACKETING. It is better to overestimate
the necessary correctibns than to underestimate
them, because in this way a bracket is more readily
‘obtained. The controlling element is that element
(either range or deflection) which is more difficult
fo sense. Range is the controlling element in range
bracketing procedure (target offset of 500 mils or
less) and deflection is the controlling element in
deflection bracketing procedure (target offset
greater than 500 mils).

128. KEEPING BURSTS ON LINE. a. If a range
change is made from a line shot, a corresponding
deflection change is necessary to keep the burst on
the OT line; conversely, if a deflection change is
made from a line shot, a corresponding range
change is required. S is the deflection shift in yards
Vhich keeps the burst on the OT line when the
ange is changed 100 yards (fig. 39).

b. When sensings are obtained, small deviations
Which might be caused by dispersion or by minor

141

Figure 39. The factor “S”.

142

regularities of the ground are ignored. Larger
eviations which might hamper future sensings are
jrrected to place bursts on the OT line.

20. DETERMINATION OF DEFLECTION
(ACTOR “5”. The deflection factor “5”, in yards,
jay be determined by—

a. Estimation and subsequent correction e firing.
b. Computation using the formula S = 1/10 T
if T is less than 600 mils).

c. Use of ranging rounds.

. EMPLOYMENT OF RANGING ROUNDS.
Ranging rounds consist of two rounds fired as
apidly as possible from the adjusting piece, the
rst round where ordered by the observer, and the
cond round at a range 400 yards greater. The
server proceeds as follows:

(1) He notes the line established by the two
nging rounds and visualizes the gun-target line.
(2) He measures the deviation (in mils) between
Irsts and converts this deviation (fig. 40) to yards
y means of the mil relation formula. Example:
Estimated range to 1st burst...... 1,500 yards.
Measured deviation in mils....... 100

Deviation in yards. ............. W

W = RM = 1.5 x 100 = 150 yards.

(3) If the observed deviation is 200 yards or
Ss the observer divides it by 4 (the distance
ween ranging rounds in hundreds of yards) to
tain the S factor.

143

(4) If the observed deviation is greater than 200
yards, the value of S is no longer equal to approx
mately one-fourth the value of the observed devia.
tion. Instead, the observer uses the following table
of approximate values in order to obtain a usable S,

For an observed

deviation of — Use an S of—
(yards) (yards)
25011 bee du uer ehe diei ЕЛЫ sre EAS 80
ЗОО dei oc IRIS ies t ttm Ema 100
АНЕ were, rer бабае E 200

For larger values of S a precise determination i;

not required.

Figure 40. Observed deviation in ranging rounds.

144

(5) If the observed deviation between ranging
rounds i is 200 yards or less, range is the controlling
Jement, and the observer uses range bracketing
procedure. If the observed deviation is greater than
200 yards, deflection is the controlling element and
he observer uses deflection bracketing procedure.
b. When the observer desires ranging rounds
jred, he includes in his initial fire message FIRE
ANGING ROUNDS. Corrections are based on
he first of the two ranging rounds.

31. CORRECTIONS AND TERMS. Listed below
Fe corrections and terms normally used by the
bserver. Any additional information that would
sist in bringing desired fire on the target may be
transmitted.

a. Left (Right) (so many yards). To correct the

eflection.
. Converged (so many yards) sheaf. To obtain
converged sheaf (or a sheaf of any desired width).
с. Converge on No. two (or other piece). To
tain a sheaf converged on the desired piece.
. Up (Down) (so many yards). To correct for
ifferences in altitude in the target area in the
itial fire message.
e. Add (Drop) (so many yards). To increase
lecrease) the range.
f. Repeat range. To obtain fire with no change in
hy element of the firing date.
g. Salvo right (left). To obtain battery salvos
ginning with the right (left) piece.

145

h. Fire for effect. To indicate that the adjust.
ment is satisfactory and that the unit is to fire fo
effect. |

i. Special corrections. To indicate that individu;
corrections for lateral distribution and variation;
in range between pieces is necessary.

j. Correction. A term used in a fire message to
indicate that an error in data has been announced
and that corrected data will follow; any change in
firing data to bring the center of impact or burst
closer to the target.

k. Lost (followed by correction to obtain obser.
vation). To indicate that the last round or volley
was not observed.

1. Cease firing, end of mission. To terminate
firing on a target.

m. Cease firing. To interrupt firing for any
reason.

132. INITIAL FIRE REQUEST. The initial fire
request sent by the observer to the fire direction
center includes the following elements in the. se
quence indicated:

Identification of the observer.

Warning order.

Location of target.

Nature of target.

Type of adjustment.

Type of ammunition.

Control.

a. Identification of the observer. The observer,

146

den necessary, identifies himself, usually by use
йа code word.

> Warning order. The observer sends FIRE
SSION to alert the fire direction center.

с. Location of target. The location of the target
jy be given in one of the following ways:

By giving a shift in yards from a point, the
on of which is known by the fire direction

МАТЕО ТО BE 2OYDS — \
ME "ALTITUDE OF BASEPOINT.

Ure 41. Designating the location of the target with respect
а known point. The observer sent to FDC: FROM BASE
INT, LEFT 400, UP 30, ADD 600 (to assure bracketing
Me target between the known point and the initial round.)

147

Known point, deflection, altitude, range. For „
ample: FROM BASE POINT, LEFT ‘FO
HUNDRED, UP THREE ZERO, ADD S
HUNDRED. The deflection and range correcti,,?
should be large enough to assure the bracketing |
the target between the known point and the init,
round. Normally the altitude element is omitti]
However, where differences in altitude between ;
known point and target would cause a large chan,
in angle of site, this element is included.

(2) By giving coordinates referring to a ma
photo map, or vertical or oblique photo. |

(3) By means of a geographic direction a
distance from a known point, as: FROM CR 2)
NORTH 400, EAST 500; or FROM CR 9j
NORTHEAST 600.

(4) By commanding a marking round from whi
he can shift to his target. Examples:

MARK BASE POINT.
MARK CHECK POINT NO. 3.
MARK CENTER OF SECTOR.

d..Nature of target. A brief description of th
target is used to give information of the importan
of the target and to indicate the best manner
attack. |
I

e. Type of adjustment. The designation of ty
of adjustment may include special sheaf or rang
spread desired, or any other special requiremet
If salvo fire is desired, the observer sends SALVE
RIGHT (LEFT). If no specific type of fire !
designated, single gun adjustment will be use

148

justment by single gun will be the normal

Types of ammunition. The observer designates
type of projectile and fuze desired. Choice of
jectile and fuze depends on type of target and
et sought. If no specific types of ammunition
designated, He with fuze superquick will be

; Control. The observer’s designation of control
consist of one of the following:

1) WILL ADJUST. This indicates that the
racy of the observer’s location of the target is
that an adjustment is considered necessary
that the observer can adjust fire. If observation
jifficult or intermittent, the observer precedes
EL ADJUST by AT MY COMMAND. In
event, the observer transmits FIRE after
ipt of READY from the fire direction center,
when he is in a position to observe. This
cedure remains in effect until a subsequent
ection is followed by the command WHEN
ADY.

2) FIRE FOR EFFECT. When transmitted as
t of the initial fire message, this indicates that
observer considers his location of the target
ре accurate, no adjustment necessary, and sur-
e fire desirable. He observes the initial fire for
st and, if necessary, sends appropriate correc-
S to increase the effect of subsequent fire on
target.

3) CANNOT OBSERVE. This indicates that the
erver will be unable to adjust the fire.

149

h. Examples of initial fire messages:
(1) FIRE MISSION
MARK BASE POINT
TROOPS
WILL ADJUST
(2) FIRE MISSION
FROM BASE POINT
RIGHT FOUR HUNDRED
UP FIVE ZERO
ADD SIX HUNDRED
THREE MACHINE GUNS
WILL ADJUST
(3) FOX OBOE BAKER
FIRE MISSION
JIG MIKE 9763
INFANTRY IN FOXHOLES
HE FUZE DELAY
AT MY COMMAND
WILL ADJUST
(4) FIRE MISSION
(42.7-93.6)
INFANTRY IN OPEN
HE FUZE DELAY
FIRE FOR EFFECT

133. INFORMATION SENT TO OBSERVER.
If a target is to be fired upon, the fire directio
center furnishes the following information to th
observer:

150

| Example
(1) Adjusting piece......... No. 3
(2) Projectile and fuze...... HE DELAY

(3) Concentration No. CONCENTRA-
assigned. TION NO. 30
(4) Time of opening бге... ҮНЕМ READY

b. If the mission cannot be fired, the observer is
otified WILL NOT FIRE, along with the reason
r not firing.

с. The observer is informed ON THE WAY as
ich round is fired during adjustment. He is notified

hen fire for effect has been completed; for ex-
nplee ROUNDS COMPLETE.

SUBSEQUENT CORRECTIONS. a. Any
ement of subsequent corrections, other than the
)orrection for range, may be omitted if no change
| that element is desired. If some element is to
e corrected, but range is not, the observer sends
le correction for that element followed by RE-
EAT RANGE. If it is desired to fire with the
ime data as the last rounds, the observer sends
EPEAT RANGE.

b. Subsequent corrections are given in the follow-
ig sequence:

(1) Deflection correction.

2) Distribution correction.

(3) Change in any special requirements (for
ample, to change from single gun to salvo fire, or
om salvo to volley fire).

(4) Change in number of rounds to be fired.

151

(5) Change in ammunition (for example, to
change from fuze superquick to fuze delay). |
(6) Range correction.

135. CORRECTION OF ERRORS. If the observe;
has transmitted his initial fire request and finds
that he has made an error in one of the elements
contained therein, he sends CORRECTION fol-
lowed only by the information pertaining to the
element which is in error. If an element is omitted,
the observer sends that element to the fire direction
center as a separate transmission.

Section IV. CONDUCT OF FIRE BY
RANGE-BRACKETING PROCEDURE

136. GENERAL. Range-bracketing procedure is
employed when the observed deviation between
ranging rounds is 200 yards or less.

137. RANGE BOUNDS. Aíter a round has been
sensed positively, the first range bound is made
large enough to bracket the target. Initial range
changes are made in hundreds of yards. Normally,
when firing at observed ranges over 2,000 ж
the initial range correction should not be less than
400 yards to establish the bracket.

138. ADJUSTMENT. a. The object of adjustment
is to enclose the target within a range bracket of
suitable depth, with deflection correct, or to obtain |
target hits. This is accomplished by successively

152

fitting the initial bracket. Fire for effect is not
jerally called for until a bracket of 100 yards
Jess is split.

>. Ranging rounds. The observer may order the
ng of ranging rounds to assist in the computation
һе S and to determine the type of bracketing to
employed.
2 To get on the line. When a burst cannot be
sed positively for range because of its deviation
m the OT line, the amount of the deviation is
ermined, in yards, and a deflection correction,
jal to that amount is made to place the next
fst on the OT line..

1. To stay on the line. When a line shot is
lained, shift of one S is made for each 100-yard
inge in range in order to keep the burst on the
"line. When a burst off the OT line is sensed
itively for range, the observer's deflection cor-
tion combines a shift to bring the Off line burst
the line, and a shift to stay on the line when
? range is changed.

). FIRE FOR EFFECT. a. Starting fire for
lect. Fire for effect is started when a suitable
acket is split, a target hit is obtained, or a salvo
ackets the target for range. If all pieces of the
ttery are calibrated (par. 156) they may be
ought into fire for effect when the base piece has
in adjusted. If they have not been calibrated, it
advisable to adjust the other guns by means of
tery salvos before commencing fire for effect.
fire for effect was accurate but insufficient the
server may command REPEAT RANGE,

153

REPEAT FIRE FOR EFFECT. The observer са,
and should make corrections while fire for effec;
being delivered.

Observer to FDC (initial RANGING BURSY

fire request) :
FIRE MISSION,
MARK BASE POINT,
FIRE RANGING ROUNDS,
WILL ADJUST.

FDC to Observer:
RANGING ROUNDS,
FUZE QUICK,

BASE POINT,
WHEN READY ....
ON THE WAY.

Remarks: OT distance from тар = 2,000 yards. With field glasses
observer measures 40 mils between ranging rounds. Observed de
= 80 yards (40 x 2). S = 20 yards (80/4). Guns to right rea
Range-bracketing to be used. No range sensing obtained. First rangin
round is 80 mils right of OT line. Observer determines shift of 14
yards (80 x 2) necessary to bring burst to OT line.

Observer to FDC:
LEFT 160,
REPEAT RANGE,

FDC to Observer:
ON THE WAY

Remarks: Small deviation is ignored. Observer decides that 200- yari
range change should give a range bracket.

Figure 42. Illustrative examples.

154

Observer to FDC:
RIGHT 40
ADD 200.

FDC to Observer:
ON THE WAY

IA to FDC:
LEFT 20,
DROP 100

[9
крс to Observer:

ON THE WAY

server to FDC:
LEFT 10,

з ROUNDS

DROP 50.

FIRE FOR EFFECT

Server to FDC:

CEASE FIRING,
END OF MISSION

Figure 42. Illustrative examples—Continued

Е 155

b. Report of observer. Upon completion of fir,
for effect the observer sends CEASE FIRING
END OF MISSION (if fire has been effective anq
sufficient) and reports the effect which has bee
obtained; for example, INFANTRY DISPERSED,

140. Employment. a. Employ range-bracketing pro.
cedure when the observed deviation between rang.
ing rounds is 200 yards or less (target offset of 500
mils or less).

b. Bring bursts to the OT line by making appro-
priate deflection corrections.

c. Keep bursts on the OT line by shifting deflec-
tion one S for each 100-yard range change.

141. PRECISION FIRE. a. Adjustment. The object
of adjustment is to determine the trial range. The
trial range is the range for the center of a 100-yard
(or l-fork) range bracket, or a range giving a
target hit.

b. Fire for effect. (1) Start fire for effect at the
trial range, and with a deflection correction which
will place the burst on the OT line. The rounds
are fired singly or in half-groups of three.

(2) Based on positive sensings, the deflection is
changed L4 5 or 10 yards, whichever is greater,
until a deflection bracket is obtained. Thereafter,
the bracket is split until the deflection is correct.
Deflection is correct when a target hit is obtained,
when a 10-yard deflection bracket is split, or when
deflection over and deflection short are obtained with
the same deflection setting.

156

(3) Obtain and report to the fire-direction center
, group of six usable range sensings.

c. Types of registration. (1) SIX ROUND REG-
STRATION. This is the type normally used. The
djusted elevation is computed by fire-direction
center as follows:

(a) If the first three rounds fired for effect are
И in the same sense and the observer has made the
ppropriate range change and has fired three more
punds, all six rounds are considered to have been
red at the mean of the two elevation used.

(b) With an equal number of overs and shorts,
e adjusted elevation is the elevation at which the
roup was fired.

(c) With unequal numbers of overs and shorts,
he difference between the number of overs and
horts (neglecting target hits) is determined. Apply
e formula:

[Difference in number of overs and ae XF

| 2 X number of rounds fired К
nd add (subtract) the result to (from) the elevation
ised (or mean elevation).

Note. If there were more overs than shorts, subtract; if
here were more shorts than overs, add.

(d) Adjusted elevation is taken to the nearest
nil. The fork used for the computation corresponds
to the elevation at which the group was fired.

Section V. CONDUCT OF FIRE BY
DEFLECTION-BRACKETING PROCEDURE

42. DEFLECTION. When the observer is con-
siderably to one side of the GT line, he can deter-

157

mine the range error more accurately than he саһ
the deflection error. Deflection, therefore, become
the controlling factor and the observer will use the
deflection-bracketing procedure described below for
adjusting on the target. This procedure is employeq
when the observed deviation between ranging
rounds is greater than 200 yards.

143. DEFLECTION BOUNDS. After a round has
been sensed positively, the first deflection bound is
made large enough to bracket the target. That is, a
bold enough change is made for the second round to
insure that a bracket is established. Normally a
deflection correction for the initial bracket should
not be less than two S’s, or greater than 400 yards,

144. COMPUTATION OF RANGE FACTOR (4).
a. In deflection bracketing, bursts are brought to
the OT line by range changes. To facilitate bringing
off line bursts to the OT line, a range factor (d)
in mils is employed. by the observer. This factor is
the angular deviation from the OT line caused by a
100-yard range change. The measured deviation oí
off line bursts is divided by this *d" to determine
the number of 100-yard range bounds necessary
to bring the bursts to the OT line. To determine
this factor the observer measures the deviation in
mils between ranging rounds and divides this angle
by 4. When the observer is so close to the target
that the use of angle measuring instruments is
impracticable, he is able to estimate the amount
. of range change necessary in this case, His estima-

158

n of range error is facilitated by the use of a
ardstick” established by ranging rounds or by
or firing in the vicinity of his target.

>» The value of "d" may be determined also,
pproximately, by computation, using the formula:
d — 1/10T (if T is less than 600 mils)

4 ADJUSTMENT. a. The object of adjustment
fo enclose the target within a deflection bracket
suitable width, with range correct, or to obtain
get hits. This is accomplished by successively
itting the initial bracket.

7. Ranging rounds. Ranging rounds are normally
ployed to determine the S and d factors.

„ To get on the line. When a burst cannot be
ised positively for deflection because of its devia-
n from the OT line, the amount of deviation is
asured in mils, and a range correction to place
e next burst on the line is determined by dividing
e deviation by d and multiplying by 100. For
ample: The observer senses deflection doubtful
0 mils right of the OT line); the d is 20; the
ece is on the right. The range change to place
e next burst on the line is 80/20 x 100 — 400
irds. The observer sends: ADD 400. It may be
cessary to bracket the line with range changes to
cure line shots. Because of dispersion and irregu-
ground, it often may be difficult to obtain
ccessive line shots. Minor deviations should be
nored unless it is impossible to obtain sensings.
d. To stay on the line. (1) When a line shot is

159

obtained, a range change of 100 yards is made A
each S deflection change in order to keep the by
on the OT line. When a burst off the OT d
sensed positively for deflection, the observe;
range correction combines (a), the range chang
to bring the off line burst to the line, and (b), th
range change to stay on the line when the deflecti,,
is changed. If the observer discovers that his ,
factor is in error, he makes the necessary correctio;
at any time during the adjustment.

(2) When a deflection bracket is obtained, it ;
split. Thereafter, bursts are kept on or near th
OT line by splitting the range bracket betwee.
sensed rounds. If positive sensings cannot |
obtained from bursts not on the OT line, th
observer must modify the range bracket to brin
off line bursts to the line, and then split the resuli
ing bracket. An example of the procedure employe
in keeping bursts on the OT line is as follow:
During adjustment a line shot has been obtaine
and the observer sensed deflection short; he decide
to shift the deflection 2 S's. S is 70; the piece is o
the right. He commands RIGHT 140, ADD 20
The next burst is to the left of the OT line, bu
he obtains a sensing of deflection over. With th
use of the range factors, he determines that
correction of DROP 40 would place the last bur:
on the OT line; therefore, he would consider hi
range bracket to be 160 yards instead of 200 yard:
and his next correction should be LEFT 70 DRO
120 (DROP 40 to get on the line, DROP 80 to spl
his effective range bracket of 160 yards). Thi
correction should place the next burst on or ver

160

near the OT line. The brackets are narrowed until
the bursts are brought within effective bursting
radius of the target, or until the target is hit.

146. FIRE FOR EFFECT. a. Starting fire for
effect. Fire for effect is started when a deflection
bracket of 100 yards is split, or when target hits
are obtained, or a salvo brackets the target for

b. Report of observer. Upon completion of fire
for effect, the observer reports as in range-bracket-
ng procedure.

17. EMPLOYMENT. a. Employ deflection-brack-
Bing procedure when the observed deviation
etween ranging rounds is greater than 200 yards
target offset greater than 500 mils).

b. Bring bursts to the OT line by making appro-
iate range corrections.

c. Keep bursts on the OT line by making a 100-
yard range change for each 1-S deflection shift.

48. PRECISION FIRE. a. Adjustment. The object
Ё adjustment is to determine the trial deflection.
"he trial deflection is a deflection giving a target
hit, or a deflection for the center of a 1-S bracket,
or a deflection for the center of a bracket of 80
yards or less when S is greater than 80 yards.

b. Fire for effect. (1) Start fire for effect at the
ial deflection, and with a range correction which
vill place the bursts on the OT line. The rounds
re fired singly or in half-groups of three. `

161

(2) Based upon positive deflection sensings, im-
-prove the deflection until it is correct. Deflection
is correct when a target hit is obtained, when a
10-yard deflection bracket is split, or when deflection
over and deflection short are obtained with the same
deflection setting.

(3) Obtain and report to fire-direction center a
group of six usable range sensings.

149. FLANK OBSERVATION. As the OT line
approaches the perpendicular to the GT line, the
observer must modify the procedure described
above for staying on the line. The true value of S
increases very rapidly as the observer's position
approaches the flank of the target; for example,
when the observer approaches to within 300 mils
of the perpendicular to the GT line, the value of S
has increased to approximately 340 yards. Based
upon firing, the observer may find it necessary to
make very small changes (or no change at all) in
range to keep burst on the OT line when a deflec-
‘tion shift is made.

Section VI. CONDUCT OF THE BATTERY

150. GENERAL. This section is concerned with
the various duties, operations, and requirements
pertaining to the firing battery.

151. INITIAL LAYING. The executive (usually
the platoon sergeant) lays the battery parallel
initially and whenever he is ordered to record base
deflection.

162

2. LAYING THE BATTERY PARALLEL. a.
tic compass. The pieces are pointed in the
eral direction of fire. The battery executive
jjaces the compass on a stake or other support
@ steady it and commands: AIMING POINT,
THIS INSTRUMENT. The gunner, upon locating
die position of the compass, reports: “Aiming point
dentified." He then turns the elbow telescope in
he direction of the compass. The executive meas-
wes the azimuth to the sight. He subtracts the
wimuth on which the guns are to be laid from the
imuth which he has measured (adding 6400 if
cessary). The remainder (minus 3200 if neces-
sry) is placed on the sight. Without moving the

ht, the tube is rotated until the sight is referred
to the compass, at which time the gunner reports:

o. 1, Ready.” The executive then commands:
MING POINT. : REFER, MARK BASE
ЕТ. ЕСТІОМ. Without disturbing the tube, the
ht is referred to the designated aiming point,
d the base deflection recorded. This process may
tepeated for each of the pieces of the battery or
the remaining guns may be laid reciprocally.

р. Using aiming circle. The executive sets up
aiming circle away from magnetic metals and at
place where it can be used as an aiming point for
pieces. He then— 4

(1) Subtracts from the declination constant plus
{#00 if necessary, the azimuth on ‘which the battery
to be laid.

2) Sets the remainder on the azimuth and
crometer scales of the aiming circle.

163

(3) Release and center the compass needle usin,
the lower motion. The 0-3200 line of the instr
ment is now directed to the announced azimuth.

(4) Reads the deflection to each gun with th,
upper motion and commands: AIMING POINT
THIS INSTRUMENT: DEFLECTION No. 1.
No. 2__, etc. (The gunner of each piece repeats this
deflection and sets it on his sight. He then move
the tube so that the sight is referred to the aiming
circle and repeats: “No. 1, ready for recheck.” This
process is repeated until the error has been reduce
to one mil or less).

(5) Commands: AIMING POINT.
FER: RECORD BASE DEFLECTION.

c. Reciprocal laying. When one gun has been
laid in the proper direction by any method, the
remaining guns of the battery may be laid on the
same azimuth as follows: At the command ON
NUMBER LAY PARALLEL, the gunner
of the specified’ gun turns his sight right or left,
without disturbing the lay of the piece, until the
vertical cross hair of his sight bisects the objective
lens of the sight on the gun to be laid. He then
takes the mil reading opposite the index on the
deflection scale and announces it to the gunner
of the gun to be laid. This gunner sets the т

: RE.

nounced reading on his own deflection scale, ап
without disturbing this reading, moves the gun
in deflection until the vertical cross hair of his
sight bisects the objective lens of the sight on tht
original gun. The first gunner checks his sight to
see that rotation of the other gun has not throw"
his sight off, If it has, he re-lays his sight on the

164

ght of the other gun and announces the new
ading. The second gunner sets the new reading
his sight and re-lays the gun so that his sight
= back on the original sight. This process is re-
ated until a difference in reading of 1 mil or less
effected, at which time the second gun is parallel

03. MINIMUM ELEVATION. As soon as the
sition is occupied, the battery executive deter-
nes the minimum elevation for mask (and if
essary for troop) clearance (par. 165) and
ords this figure. In case it is necessary to deter-
е more than one minimum elevation in the
gone of fire, the executive records it, for example:

imuth 4850 to 5200, minimum elevation 55; 5200
9650, minimum elevation 42.

CONVERSION OF FIRE REQUESTS
ID OBSERVER CORRECTIONS. Firing data
Asmitted from the FO to the fire direction
iter is in yards for range and deflection. In order
‘this information to be of use to the gunner it
ist be converted to mils. The fire direction center
lverts yards of deflection to mils by means of
i mil relation formula, a firing chart, or a deflec-
n conversion table, and converts yards of range
mils of elevation by means of a firing table.

. FIRE COMMANDS. a. General. For general
cussion of fire.commands, see paragraph 95. The
owing subparagraphs discuss fire commands as
lied to indirect fire.

165

b. Sequence. (1) The sequence for transmission
fire commands for indirect fire is as follows:

(a) Pieces to follow commands.

(b) Type of ammunition.

(d) Direction.

(e) Distribution.

(f) Pieces to fire.

(g) Method of fire.

(h) Elevation (the order to load the piece).

(i) Command to open fire.

(2) All бге commands follow the general sequen
outlined above. However, in certain fire command;
those elements which are not necessary for th:
proper conduct of fire are omitted.

c. Initial fire command. (1) Pieces to follow com.
mands. When two or more guns are operating as 4
unit, the word BATTERY designates that all piece
are to follow commands. If it is desired that only
one gun follow commands, the number of that gun is
substituted.

(2) Type of ammunition. The type of ammunition
to be used is specified in the fire command as: HE,
HEAT, etc.

(3) Fuze. Unless otherwise specified, fuze supe
quick is used.

(4) Direction. Direction is indicated by BASE
DEFLECTION or BASE DEFLECTION RIGHT
(LEFT) (SO MUCH).

(5) (a) Distribution. This element deals with th
distribution of the bursts in the impact area. T?

166

lose the sheaf the command is ON NUMBER .

SLOSE . . . To open the sheaf the command is

N NUMBER. — OPEN. . The number of mils

announced depends on the distance in yards that

je bursts are to be moved and the range at which
he battery is to fire. Upon receipt of this command,
he gunners set off on their sights the product of

е directed change and the number of intervals

hich exist between their pieces and the one desig-

ated, adding this product if the piece is to move
the left and subtracting if it is to move to the
ће. Then the gunners re-lay their pieces. Individ-

] corrections to produce a regular sheaf are also

cluded in this element of the fire command.

(b) pU

Sheaf. A sheaf consists of the planes of
fire of two or more pieces.

2. Width of sheaf. 'The width of the sheaf is
the lateral interval between flank bursts.

3. Parallel sheaf. A parallel sheaf is one in
which the planes of fire are parallel.

4. Converged sheaf. When the battery is fired
with bursts converged on a point target,
the planes of fire constituted converged
sheaf (fig. 44).

5. Obpen sheaf. An open sheaf is one covering
the maximum front without shifting. (Max-
mum front is based upon the effective
bursting radius of the HE shell).

6. Regular sheaf. A regular sheaf is one in
which the bursts are approximately on a
line for range and are equally spaced
laterally.

167

Figure 43. Parallel sheaf.

(6) Pieces to fire. This element of the fire command
designates the specific weapon(s) which will fire.

(7) Method of fire. The method of fire is always
announced in the initial fire command. If the battery
is the fire unit, the command may be No. 1 (3, etc.,

168

4 „ек
Е
Q У wom oF

Figure 44. Converged sheaf.

hichever is the base gun) ONE ROUND. At
€ command BATTERY RIGHT (LEFT), battery
Ше is delivered successively from the right (left)
nk at short fixed intervals. The normal interval is
“Seconds. If a different interval is desired, the

169

command is: BATTERY RIGHT (LEFT), 4;
(SO MANY) SECONDS; or BATTERY RIGH
(LEFT), AT MY COMMAND. At the comman,
BATTERY ONE ROUND (TWO ROUNDs
etc.), all guns fire the first round simultaneously
This is.known as volley fire. If a multiple numbe,
of rounds are to be fired, the initial volley will },
fired on the command of the battery executive, and
all subsequent rounds will be fired individually p,
each gunner as soon as he can re-load and re-lay.

(8) Elevation. The elevation is always announce)
in all fire commands. The command for elevation
is the command to load the piece. In the fire com.
mand the word "elevation" does not precede th:
numerical value unless required for clarity.

(9) Command to open fire. This element is given а;
FIRE.

d. Subsequent fire commands. In subsequent
commands only those elements which are to be
changed are mentioned, with the exception of the
elevation and the command to fire.

156. CALIBRATION. a. Definition. Calibration i:
the comparison of the shooting qualities of a given
piece with those of another piece taken as standard
A calibration correction is a correction to make a pied
fire in agreement with the piece taken as standard.

b. Necessity for calibration. The principles oí
conduct of fire with a battery are based on the
assumption that if all pieces of a battery are fired
under the same conditions, the rounds will fall at
approximately the same range. There are, however.

170

ariations due to slight differences in the dimen-
ons of the chambers and in wear in the venturis.
then the variations are determined by calibration,
)mpensating corrections may be made.

c. Method. Calibration is normally accomplished
б registration of the individual guns on a common
rget. (See par. 158.)

Section VII. PREARRANGED FIRES

7. GENERAL. a. Definition. (1) Prearranged fires.
res for which firing data are prepared in advance
e known as prearranged fires. Prearranged fires
re used to aid in the support of an attack or de-
ase, and for firing during periods of poor visibility
darkness. Normally they are unobserved fires.
pncentrations should be prepared for gaps in the
'earranged close-defensive fires of other supporting
eapons, for likely avenues of approach, for possible
Ssembly areas, for known enemy positions, and
)r areas which are likely to be occupied by enemy
üpporting weapons or observers. Requests for
)ncentrations on gaps in the prearranged close-
efensive fires of other supporting weapons will be
Пхеп first priority over requests for all other types
f fire.

(2) Concentration. A concentration is a volume of
re placed on an area within a limited time.

(3) Registration. Firing data will be corrected by
]eistration on a known point, as near the time of
ring as the tactical situation permits.

171

(4) K. The elevation correction factor obtained
from registration on a base point is known as Қ
(see par. 158).

(5) Announcement of data. Data determined by
precise methods will be announced to the smallest
graduation of the scale involved.

b. Direction. As prearranged fires are normally
unobserved, the most precise methods of obtaining
the initial data will be used, preferably by the em-
ployment of maps. If maps are not available, data
will be obtained by the employment of fire control
instruments and rapid plotting. When using maps,
the positions of the gun and the target are deter-
mined and a line drawn connecting the two. The
azimuth can then be measured directly with a
protractor.

c. Angle of site. Computed as in paragraph 123.

d. Elevation. Determined as in paragraph 124.

e. New targets. New targets are plotted and the
shift measured with a protractor.

f. Data cards. (1) Firing data are placed on a
data card; a suggested form for such cards is shown
in figure 45. Any other similar data card suiting
the needs of the platoon or section leader is satis-
factory.

(2) Upon the occupation of a position, these
cards should be prepared for the primary positions,
and when time permits, for alternate and supple-
mentary positions as 'well.

(3) When a section (platoon) has a secondary
target area, accurate data should be prepared for at
least one concentration in that area.

172

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173

g. Notes on data card (fig. 45). Concentration,
for the 75-mm rifle are identified by the number 75
followed by the number of the concentration. The
following subparagraphs are numbered to corre.
spond to similarly numbered columns on the sug.
gested data card.

(1) Requests for fires are made by requesting
“Concentration No. ( )", or in accordance with a
prescribed signal.

(2) In identifying a target, its location and de-
scription are included (when necessary).

(3) Time of fire is indicated in this column.
Signals (if used) for firing particular concentrations
are also included.

(4) The range, GT, is entered as measured; below
it is entered the corresponding elevation in mils.
When the range GT, as measured, is other than in
even 100 yards, the elevation is obtained by inter-
polation.

(5) Angles of shift measured at the OP from the |
base point, and azimuths to the centers of the
various concentrations, are entered in this column.
Azimuth to the base point is always shown.

(6) The range, OT, and the angle of site, OT,
are entered in this column to permit ready sub-
stitution in the mil relation. This column T
employed in firing from defilade.

(7) This column may show the method of adjust-
ment. á

(8) This column specifies the type of projectile;
this and the data in the columns to the right form
the basis for the necessary fire commands.

174

(9) The fuze setting is indicated only when it is
be DELAY.

(10) The angle of shift for the guns from base
int to target is entered in this column.

(11) If a command to close the fires is required,
is inserted in this column. No. 3 gun is normally
‚ base piece.

(12) The elevation constant (K) is entered in
is column.

(13) The method of fire, including the number of
ands, is shown.

(14) The corrected elevation (see par. 124), deter-

…[truncated]

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