Document text
FM 6-75
MHI
Copy 3 ^ —
WAR DEPARTMENT
FIELD ARTILLERY
FIELD MANUAL
*
SERVICE OF THE PIECE
106-MM HOWITZER, M2, TRUCK-DRAWN
December 12, 1941
FM 6-75
FIELD ARTILLERY
FIELD MANUAL
j-
SERVICE OF THE PIECE
105-MM HOWITZER, M2, TRUCK-DRAWN
Prepared under direction of the
Chief of Field Artillery
UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON : 1941
For sale by the Superintendent of Documents, Washington, D. C.
WAR DEPARTMENT,
Washington, December 12, 1941.
FM 6-75, Field Artillery Field Manual, Service of the
Piece — 105-mm Howitzer M2, Truck-drawn, is published for
the information and guidance of all concerned.
[A. G. 062.11 (10-14-41).]
By order of the Secretary of War:
G. C. MARSHALL
Chief of Staff.
Official :
E. S. ADAMS,
Major General,
The Adjutant General .
Distribution:
Bn and H 6 (4) ; IB 6 (10) ; IB 6 (6) ; IBn 6 (7) ;
IC 6 (16) ; IC and H 9 (2).
(For explanation of symbols see FM 21-6.)
II
TABLE OF CONTENTS
Section I. General. Paragraph Page
Purpose and scope 1 1
References 2 1
Definitions and terms 3 1
II. Organization.
Composition 4 2
Formation 5 2
III. Posts: Mounting and dismounting.
Posts of howitzer squad 6 3
To post howitzer squads 7 3
Posts of cannoneers 8 3
To post cannoneers 9 4
To mount 10 4
To dismount 11 6
IV. Movements of the carriages by hand.
Coupled 12 7
Uncoupled 13 7
V. Uncoupling and coupling.
Uncoupling 14 9
Coupling 15 10
VT. Prepare for action and march order.
To prepare for action 16 10
Posts of cannoneers, , piece un-
coupled 17 13
March order 18 14
VH. Duties in firing.
General 19 17
Chief of section 20 17
Gunner 21 22
No. 1 22 26
No. 2 23 29
No. 3 24 30
No. 4 25 31
No. 5 26 31
No. 6 27 32
No. 7 28 32
VIII. Additional information on the service of
the piece.
Accuracy in laying 29 33
Fire at will 30 33
Aiming posts 31 34
Displacement correction 32 34
Reporting errors 33 34
Cease firing 34 35
Suspend firing 35 35
Change in data during firing 36 35
To unload piece 37 35
Misfires 38 36
Ammunition 39 36
Section data board 40 36
III
TABLE OF CONTENTS
Section
Paragraph Page
IX. Care and maintenance of materiel.
General 41 37
Inspection 42 38
Cleaning 43 38
Lubrication 44 39
Protection against chemicals 45 41
Recoil mechanism 46 42
Barrel assembly and slides 47 45
Breech and firing mechanisms 48 47
Equilibrator 49 49
Elevating mechanism and cradle
trunnion bearings ' 50 50
Wheels and wheel bearings 51 50
Brake mechanism 52 52
Sighting and fire-control equip-
ment 53 53
IV
FM 6-75
FIELD ARTILLERY FIELD MANUAL
SERVICE OF THE PIECE
105-MM HOWITZER, M2, TRUCK-DRAWN
Section I
GENERAL
■ 1. Purpose and Scope. — T his manual prescribes the duties to
be performed in the service of the piece by the personnel
normally assigned to one howitzer section of the firing
battery.
■ 2. References. — a. Description, operation , functioning, and
care of materiel . — TM 9-325; SNL C-21.
b. Description and operation of fire-control and sighting
equipment . — TM 9-325; SNL F-l.
c. Ammunition. — TM 9-325; TM 9-1900; SNL R-l.
d. Cleaning and preserving materials. — TM 9-850; SNL K-l.
e. Automotive driver. — PM 25-10.
f. Maneuvers of battery. — Part Two, PM 6-5.
g. Safety precautions in firing. — AR 750-10; PM 6-40.
h. Firing battery . — FM 6-40.
i. Gunnery.- — FM 6-40.
j. Reconnaissance , occupation, and organization of posi-
tion. — FM 6-20.
■ 3. Definitions and Terms. — a. Section. — Tables of Organi-
zation prescribe the personnel and materiel comprising a sec-
tion of a battery. In this manual the term is frequently used
to designate a section of the firing battery. In this restricted
sense, a howitzer section is composed of one piece and the
additional materiel and the personnel required to serve that
piece.
b. Coupled. — A piece is said to be coupled when its lunette
is attached to the pintle of a truck or other prime mover.
c. Uncoupled. — A piece is said to be uncoupled when its
lunette is detached from the pintle of a truck or other prime
mover and the trail rests on the ground.
d. Front. — The front in a section, carriages coupled, is the
direction in which the trail points; carriages uncoupled, the
direction in which the muzzle of the piece points.
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FIELD ARTILLERY
e. Right (left) . — The direction right (left) is the right (left)
of one facing the front.
/. In battery. — A howitzer is said to be in battery when it
is in its normal firing position.
Section II
ORGANIZATION
■ 4. Composition. — a. Howitzer squad. — A howitzer squad
consists of the gunner and seven cannoneers numbered from
1 to 7.
b. Howitzer section. — A howitzer section consists of a chief
of section, a howitzer squad, a driver, and additional can-
noneers and an assistant driver who may be assigned or
attached. The additional cannoneers act as reliefs or are
assigned to other duties as the chief of section may direct.
When the section uncouples for drill or for firing, the chief
of section remains at the position of the piece and commands
the howitzer squad.
c. Ammunition squad . — (1) An ammunition squad consists
of an ammunition corporal and cannoneers as prescribed
in Tables of Organization. These cannoneers are numbered
consecutively, beginning with No. 1, and are assigned to the
ammunition vehicles of the ammunition (fifth) section.
(2) Posts and movements prescribed hereinafter for the
howitzer squad apply with obvious modifications to an ammu-
nition squad.
d. Ammunition section . — The ammunition section consists
of the chief of section, the ammunition squad, and the drivers
of the ammunition trucks of the ammunition (fifth) section.
■ 5. Formation. — a. Order of formation . — A howitzer squad
is formed as shown in figure 1. Higher -numbered cannon-
eers, if present, form in order on the left of No. 7.
b. To form. — (1) The place of formation is indicated and
the command given thus, for example: 1. in front (rear)
of your pieces, or 1. on the road facing the park, 2. FALL
IN. Each gunner repeats the command fall in and hastens
to place himself, faced in the proper direction, at the point
where the right of his squad is to rest. The cannoneers
move at the double time and assemble at attention in their
proper places. For the first formation of the howitzer
2
105-MM HOWITZER M2 5-8
squads for any drill or exercise, the caution, “As howitzer
squads,” precedes the command. The chief of section, if
present, supervises the formation.
(2) In case the front or rear of the carriages is desig-
nated, each squad falls in at its post (par. 6) .
c. To call off. — (1) The command is: CALL OFF. The can-
noneer on the left of the gunner calls off “One”; the can-
noneer on the left of No. 1, “Two”; and so on.
(2) After having called off, if a subsequent formation
is ordered, the cannoneers fall in at once in their proper
order.
Figure 1. — Formation of howitzer squad.
Section III
POSTS: MOUNTING AND DISMOUNTING
B 6. Posts of Howitzer Squads. — a. Carriages coupled . —
(1) In front of piece. — The squad is in line facing to the
front, its center 2 paces from the front of the truck.
(2) In rear of piece. — The squad is in line facing to the
front, its center 2 paces from the muzzle of the piece.
b. Carriages uncoupled . — In rear of piece . — The squad is
in line facing to the front, its center 2 paces from the end
of the trail.
B 7. To Post Howitzer Squads. — The squads having been
marched to the vicinity of the carriages are posted at the
command squads in front (rear) of your pieces. Each
gunner marches his squad to its carriage and posts it in
the position indicated.
■ 8. Posts of Cannoneers. — a. Carriages coupled. — The can-
noneers of the howitzer squad are posted as shown in figure 2.
All are 2 feet outside the wheels and facing to the front.
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FIELD ARTILLERY
Higher-numbered cannoneers, if present, are posted as pre-
scribed by the chief of section,
b. Carriages uncoupled . — See paragraph 17 and figure 5.
■ 9. To Post Cannoneers. — a. The command is: 1. can-
noneers, 2. POSTS. Each gunner repeats the command posts.
The cannoneers move at the double time to their posts.
b. For preliminary instruction, the squads on entering the
park are first posted with their carriages, and cannoneers are
then sent to their posts by the foregoing command. The
command is general, however, and is applicable when the can-
noneers are in or out of ranks, at a halt or marching, and
when the carriages are coupled or uncoupled.
■ 10. To Mount. — a. The command is: 1. cannoneers, pre-
pare to mount, 2. MOUNT. At the first command, the can-
noneers move at the double time to positions shown in
figure 3. At the second command, the cannoneers of both
columns mount in the order from head to rear, and take
seats as shown in figure 4. Each cannoneer is assisted by
the one directly behind (or in front in the case of the last
cannoneer in column) to insure promptness and prevention
of injuries. If the chief of section and driver are to be
included in the movement, the command is: 1 . prepare to
mount, 2. MOUNT. At the first command, the chief of section
takes position 2 feet from the right side of the truck and op-
posite his seat; the driver takes position 2 feet from the
left side of the truck and opposite his seat; each opens his
door and faces to the front holding the door open. At the
second command, they mount, take seats, and close their
doors.
b. If the command is: 1. cannoneers, 2. MOUNT, the can-
noneers execute, at the command mount, all that has been
prescribed for the commands cannoneers, prepare to> mount
and mount. If the chief of section and driver are to be
included in this movement, the command is: MOUNT.
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FIELD ARTILLERY
Figure 3. — Posts of cannoneers in prepare to mount.
■ 11. To Dismount. — a. The command is: 1. cannoneers,
prepare to dismount, 2. DISMOUNT. At the first command,
the cannoneers assume standing positions facing the rear
of the truck; at the second command, they jump to the
6
105 -MM HOWITZER M2
11-13
ground and, at the double time, take posts as shown in figure
2. If the chief of section and driver are to be included in
this movement, the command is: 1 . prepare to dismount, 2.
DISMOUNT. At the first command, the chief of section and
driver unlatch their doors and hold them slightly open; at
the second command, they promptly dismount, close their
doors, and take posts as shown in figure 2.
b. If the command is: 1. cannoneers, 2. DISMOUNT, the
cannoneers execute, at the command dismount, all that has
been prescribed for the commands cannoneers prepare to dis-
mount and dismount. If the chief of section and driver are
to be included in this movement, the command is: DIS-
MOUNT.
Section IV
MOVEMENTS OP THE CARRIAGES BY HAND
■ 12. Coupled. — The carriages are not moved by hand when
coupled.
■ 13. Uncoupled. — a. The command is: 1. pieces forward
(backward) , 2. MARCH. At the first command, the gunner
and No. 1 remove the trail lock pins and place them in the
traveling positions. Nos. 2 and 6 on the left trail and 3 and
7 on the right trail manipulate the trails as directed by No.
4 so that the axle locks may be locked by Nos. 4 and 5,
working on the left and right, respectively. Nos. 2, 3, 6, and 7
close the trails, and No. 6, assisted by No. 7, fastens the trail
lock. The gunner and No. 1 release the hand brakes. Nos.
2 and 6 and Nos. 3 and 7 then grasp the trail handles on
the left and right, respectively. No. 4 grasps the left wheel,
No. 5 the right wheel. The gunner and No. 1 place themselves
advantageously at the breech of the piece in moving forward;
at the muzzle in moving backward. Higher- numbered can-
noneers, if present, are employed as directed by the chief
of section. If the situation requires the use of prolonges,
Nos. 4 and 5, under the direction of the chief of section,
will obtain the prolonges and attach them to the hooks
on the left and right axles, respectively. Personnel desig-
nated by the battery executive to assist in the movement of
the piece will take position and pull on the prolonges as
directed by the chief of section.
7
105 -MM HOWITZER M2
13-14
b. At the command march, all move the piece forward
(backward) under the direction of the chief of section. When
the piece is being moved up or down steep slopes, the gunner
and No. 1 assist by alternately setting and releasing the left
and right brakes, thus permitting the piece to be pivoted
about the alternately locked wheels. At the command halt,
the piece is stopped and reestablished in the firing position ;
all resume their posts (par. 17) .
Section V
UNCOUPLING AND COUPLING
■ 14. Uncoupling. — a. General. — At drills, trucks are posted
as directed by the battery commander. In active service and
in instruction simulating it, the trucks are conducted by the
first sergeant to a place previously designated by the battery
commander; there they are disposed so as to take the best
advantage of cover and concealment. If no cover and con-
cealment are available, the trucks are located in rear of either
flank, faced to the front, with wide intervals between them.
b. To fire to front. — The command is; ACTION FRONT.
If marching, the trucks halt at the command or signal. The
cannoneers, if mounted, dismount after the trucks have
halted.
(1) Pieces . — The gunner and No. 1 hasten to the wheels
nearest their respective posts. Nos. 2, 3, 6, and 7 hasten to
the trail handles, even numbered cannoneers on the right, odd
numbers on the left. Nos. 4 and 5 go to the muzzle of the
piece, and assist by placing their weight on the tube. No. 3
disengages the electric brake cable and safety chain from the
prime mover. No. 2 unlatches the~T5ihtTe~and, assisted by
Nos. 3, 6, and 7, raises the trail from the pintle; the gunner
sets the left wheel brake. Nos. 2, 3, 4, 5, 6, and 7 swing the
piece 180° clockwise. No. 3 releases the drawbar lock and
turns the drawbar 180°, latching it in the firing position.
Nos. 2, 3, 6, and 7 then lower the trail to the ground. No. 1
sets the right wheel brake. The gunner and all cannoneers
then unload the ammunition, tools, and accessories and ar-
range them in an orderly and convenient manner to the left
of the piece. When the unloading has been completed, the
chief of section commands or signals drive on. The gunner
and cannoneers take their posts (par. 17) .
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14-16
FIELD ARTILLERY
(2) Trucks . — At the command drive on, the trucks move
out and are conducted by the first sergeant to their previously
designated position.
c. To fire to rear. — The command is: ACTION REAR. The
movement is executed according to the principles of action
front. The piece is not turned after uncoupling.
d. To fire to fiank.—The command is: ACTION RIGHT
(LEFT) . The movement is executed according to the princi-
ples of action front, with the following modifications: After
the piece is uncoupled, the trail is turned 90° away from the
direction of fire, and the piece is run forward sufficiently to
clear the track made by the truck; articles unloaded from the
truck are placed on the ground so as to clear the track made
by the truck.
3 15. Coupling. — a. The pieces being in position and in
march order, the command is: COUPLE. The trucks, under
the command of the first sergeant, approach the position from
the right (left) flank. As each truck approaches its piece, it
turns to the left (right) and halts in prolongation of the trail
of the piece.
b. All cannoneers working together under the direction of
the chief of section load the tools, accessories, and unex-
pended ammunition. Nos. 2, 3, 6, and 7 hasten to the trail
handles, even-numbered cannoneers on the left, odd-num-
bered on the right. Nos. 4 and 5 hasten to the muzzle of
the piece. The gunner and No. 1 release the brakes. The
truck, upon signal from the chief of section, is maneuvered
backward until the pintle is almost over the lunette. Nos.
2, 3, 6, and 7 then raise the trail and, after No. 3 has placed
the drawbar in traveling position, place the lunette over the
pintle, No. 2 latching the pintle. Nos. 4 and 5 assist by
placing their weight on the tube. No. 3 engages the electric
brake cable and safety chain to the prime mover. The chief
of section verifies that the brakes are operating properly.
All cannoneers take their posts.
Section VI
PREPARE FOR ACTION AND MARCH ORDER
■ 16. To Prepare for Action. — a. The piece being in posi-
tion uncoupled, the command is: PREPARE FOR ACTION.
Duties of individuals are as follows:
10
105- MM HOWITZER M2
16
(1) Chief of section . — (a) Supervises the work of the
cannoneers.
(b) Inspects the materiel; verifies the fact that the recoil
mechanism contains the proper amount of oil and that all
is in order; and, when the operations have been completed,
reports to the executive, “Sir, No. (so-and-so) in order,” or
reports any defects that the section cannot remedy without
delay.
(2) Gunner \ — (a) Assisted by No. 1, removes the breech
end of the howitzer cover.
(b) Releases the left hand brake momentarily while trails
are being spread, to permit action of the equalizer axle.
(c) Places the left trail lock pin in the firing position.
id) Removes the panoramic telescope from its case, and
seats it in the telescope mount.
(e) Uncovers the telescope mount bubbles; sets the index
of the rotating head at zero, the deflection at zero, and
levels both bubbles.
(/) Takes his post.
(3) No, 1 . — (a) Releases the traveling lock.
(b) Assists the gunner in removing the breech end of the
howitzer cover, throwing the cover to the right of the right
wheel.
(e) Releases the right hand brake momentarily while
trails are being spread, to permit action of the equalizer
axle.
(d) Places the right trail lockpin in the firing position.
(e) Operates elevation handwheel to assist No. 4 in unlock-
ing cradle lock.
(/) Uncovers the range quadrant bubbles; if directed by
the executive, replaces the range drum for Charge V with
the designated drum; sets site 300 and range 3,000, and levels
the bubbles.
(g) Operates the breech mechanism, and examines the
breechblock, chamber, and bore, cleaning any parts requiring
it; leaves the breech open.
(h) When so directed by the executive, removes the elbow
telescope from its case and seats it in its mount.
( i ) Takes his post.
(4) No. 2. — (a) Spreads the left trail, assisted by No. 6,
when No. 4 calls “Spread.”
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16
FIELD ARTILLERY
( b ) Removes the rammer staff from its traveling position,
assembles it to the rammer (bore brush), and places it to
the right of the piece.
(c) When so directed, assists No. 1 in cleaning the breech
mechanism, chamber, and bore of the howitzer.
id) Folds the muzzle and breech ends of the howitzer
cover, and places them on the ground to the right of the
right wheel of the howitzer.
(e) Takes his post.
(5) — (a) Unlocks the drawbar lock, and turns and
locks the drawbar in firing position.
(b) Spreads the right trail, assisted by No. 7, when No, 4
calls “Spread.”
(c) Arranges the ammunition and tools, assisted by Nos.
4, 5, 6, and 7.
( d ) Obtains the fuze setter from the section chest, and
places it convenient to the position of the ammunition.
(e) Takes his post.
(6) No._4. — (a) Unlocks the left axle lock from the travel-
ing position and latches it in the firing position; when he
sees that both axle locks are unlocked, calls “Spread,” to
inform Nos. 2 and 3 that trails may be spread.
(b) Unlocks the cradle lock, assisted by No. 1 operating
the elevation handwheel, and latches it in firing position.
(c) Removes the muzzle end of the howitzer cover, assisted
by No. 5.
( d ) When so directed, lowers left top shield, and locks it
in the lowered position.
(e) Assists No. 3 in arranging the ammunition and tools.
(/) Takes his post.
(7) No. 5 . — (a) Unlocks the right axle lock from the travel-
ing position and latches it in the firing position.
(b) Assists No. 4 to remove the muzzle end of the howitzer
cover, and throws it on the ground to the right of the right
wheel.
(c) Removes the aiming posts from the traveling position
and places them beside the rammer staff.
id) Assists No. 3 in arranging the ammunition and tools.
(e) Takes his post.
(8) No. 6. — (a) Unlocks the trail lock.
(b) Removes the trail handspike from its traveling position
and places it in its socket on the left trail.
12
105 -MM HOWITZER M2
16-17
(c) Assists No. 2 in spreading the left trail.
( d ) Places the section chest, assisted by No. 7, immediately
to the left of the piece.
(e) Assists No. 3 in arranging the ammunition and tools.
(/) Distributes waste to the cannoneers.
(gr) Takes his post.
(9) .iyo. 7. — (a) Assists No. 3 to spread the right trail.
( b ) Assists No. 6 to place the section chest to the left
of the piece.
(c) Assists No. 3 in arranging the ammunition and tools.
(d) Takes his post.
b. The coupled piece may be partially prepared for action
before reaching the firing position. The duties of the can-
noneers are the same as in preparing for action when the
piece is uncoupled, but only such operations as are practi-
cable are carried out. Immediately after the piece is estab-
lished in position, preparation for action is completed without
command, and the cannoneers take their posts for firing the
piece.
c. If prepare for action has not been ordered before the
piece is established in the firing position, the command is
habitually given by the chief of section as soon as the piece
has been uncoupled. If this is not desired, the caution, “Do
not prepare for action,” must be given.
■ 17. Posts of Cannoneers, Piece Uncoupled (fig. 5) . — a. The
piece having been uncoupled, posts are taken as follows:
(1) Chief of section . — The chief of section goes where he
can control the service of the piece, hear commands, and
perform his duties effectively. A convenient post is between
the trail spades and on line with them.
(2) Gunner. — Immediately behind the left wheel and
outside the trail.
(3) No. 1 . — Immediately behind the right wheel and
outside the trail.
(4) No. 2 . — Three feet in rear of the gunner, covering him,
and inside the trail.
(5) No. 3 . — Two feet to the left of No. 2.
(6) No. 4. — Two feet in rear of No. 3, covering him.
(7) No. 5. — Two feet to the left of No. 4.
(8) No. 6. — Two feet to the left of No. 5.
(9) No. 7. — Two feet in rear of No. 5, covering him.
426841 ° — 41 ~
13
17-18
FIELD ARTILLERY
b. At drill all stand at attention at their posts facing the
front. In firing and combat, minor modifications of these
posts are required for the more efficient performance of the
duties in the service of the piece, and for protection of the
personnel. Higher-numbered cannoneers, if present, take
posts as prescribed by the chief of section.
c. In order to exercise the cannoneers in all the duties
connected with the service of the piece and to lend variety
to the drill, the posts of individual cannoneers should be
changed frequently. The cannoneers being at their posts,
howitzer coupled or uncoupled, the command is: 1 . change
posts, 2. MARCH. In each squad No. 1 quickly takes the
post of No. 2, No. 2 of No. 3, and so on, No. 7 taking the post
of No. 1. The gunner and higher-numbered cannoneers
change only when specifically directed; the command is: 1.
GUNNER AND CANNONEERS CHANGE POSTS, 2. MARCH. In each
squad, the gunner quickly takes the post of No. 1, No. 1 of
No. 2, and so on. The highest-numbered cannoneer takes
the post of the gunner.
B 18. March Order. — a. The howitzer being uncoupled and
prepared for action, to resume the order for marching, the
® ©
(z)
Figure 5. — Posts of cannoneers, howitzer uncoupled.
14
105 -MM HOWITZER M2
18
command is: MARCH ORDER. Duties of individuals are
as follows:
(1) Chief of section. — (a) Supervises the work of the
cannoneers.
(b) Inspects the materiel; makes sure that the piece is
not loaded and that the traveling lock and cradle lock are
locked in the traveling position; and, when the operations
have been completed, reports to the executive, “Sir, No.
(so-and-so) in order,” or reports any defects which the
section cannot remedy without delay.
(2) Gunner . — (a) Places the piece in the center of traverse.
(b) Removes left trail lock pin from the firing position
and places it in the traveling position.
(c) Sets the rotating head and deflection at zero and
closes the covers on the telescope mount leveling bubbles.
( d ) Removes the telescope from the mount, returns it to
its case, and locks the case.
(e) Replaces the breech end of the howitzer cover, assisted
by No. 1.
(/) Takes his post.
(3) No. 1. — (a) Operates elevation handwheel to assist
No. 4 in locking cradle lock.
(b) Removes the right trail lock pin from the firing posi-
tion and places it in traveling position.
(c) Inspects the chamber to see that piece is unloaded and
closes breech.
id) Locks the traveling lock, after the trails have been
closed and locked.
(e) Assists the gunner in replacing the breech end of the
howitzer cover.
(/) Takes his post.
(4) No. 2. — ( a ) Closes the left trail, assisted by No. 6.
(b) Disassembles the rammer staff; removes the rammer
(bore brush) and places it in the section chest; secures the
rammer staff in its traveling position on the trail.
(c) Takes his post.
(5) No. 3. — (a) Closes the right trail, assisted by No. 7.
(b) Turns and locks the drawbar in its traveling position.
(c) Places the fuze setter in the section chest.
(<£) Prepares ammunition and tools, assisted by Nos. 4, 5,
6, and 7, for loading in the prime mover.
(e) Takes his post.
15
18
FIELD ARTILLERY
(6) No. 4. — (a) Locks the cradle lock in the traveling
position, assisted by No. 1 operating the elevation handwheel.
( b ) Locks the left axle lock in the traveling position.
(c) Raises and locks the left top shield, if down.
id) Replaces the muzzle end of the howitzer cover,
assisted by No. 5.
(e) Assists No. 3 in preparing the ammunition and tools
for loading in the prime mover.
(/) Takes his post.
(7) No. 5. — (a) Locks the right axle lock in the traveling
position.
(b) Assists No. 4 in replacing the muzzle end cf the howitzer
cover.
(c) Secures the aiming posts in the traveling position on
the trail.
(d) Assists No. 3 in preparing the ammunition and tools
for loading in the prime mover.
(e) Takes his post.
(8) No. 6. — (a) Assists No. 2 in closing the left trail.
(b) Assisted by No. 7, locks trail lock.
(c) Removes the trail handspike from the left trail and
secures it in its traveling position,
(d) Prepares the section chest for loading in the prime
mover, assisted by No. 7.
(e) Assists No. 3 in preparing the ammunition and tools
for loading in the prime mover.
(/) Takes his post.
(9) No. 7. — (a) Assists No. 3 in closing the right trail.
(b) Assists No. 6 in locking the trail lock.
(c) Assists No. 3 in placing the drawbar in the traveling
position.
id) Assists No. 6 in preparing the section chest for loading
in the prime mover.
(e) Assists No. 3 in preparing the ammunition and tools
for loading in the prime mover.
(/) Takes his post.
b. To resume fire in another position . — (1) If firing is to be
resumed shortly in another position to which the piece must
be towed by its prime mover, the command march order is
not given. In this case, at the command for coupling, only
such of the operations incident to march order are per-
16
105 -MM HOWITZER M2
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formed as are necessary for the movement of the piece and
for the care and security of the equipment.
(2) If the command march order is given while the piece
is coupled, the operations pertaining to march order are
completed.
Section VII
DUTIES IN FIRING
H 19. General. — In general the duties in firing are as follows:
a. The chief of section is responsible that all duties are
properly performed, all commands executed, and all safety
precautions observed.
b. The gunner sets the announced deflection, lays for direc-
tion, and refers the piece.
c. No. 1 sets the announced site and range (elevation),
opens and closes the breech, and fires the piece.
d. No. 2 loads the piece.
e. No. 3 operates the fuze setter and makes the proper set-
ting of fuzes.
/. No. 4 assists No. 3 in setting fuzes, and passes the rounds
to No. 2 for loading.
g. No. 5, assisted by Nos. 6 and 7, prepares charges and
passes the reassembled round to No. 4.
h. Nos. 6 and 7 remove ammunition from the containers
and assist No. 5 in preparing charges and reassembling
rounds. No. 7 keeps empty cartridge cases out of the way of
the cannoneers.
■ 20. Chief of Section. — a. Enumeration of duties. — (1) To
lay for elevation, assisted by No. 1, when the gunner’s
quadrant is used.
(2) To measure the elevation (range).
(3) (a) To measure the minimum quadrant elevation.
( b ) To measure the minimum range (elevation).
(4) To indicate to the gunner the aiming point, the refer-
ring point, or the target.
(5) To follow fire commands.
(6) To indicate when the piece is ready to fire.
(7) To give the command to fire except when firing on
moving targets with direct laying.
(8) To report errors and other unusual incidents of fire to
the executive.
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20
FIELD ARTILLERY
(9) To conduct prearranged firing schedules.
(10) To record basic data.
(11) To observe and frequently check the functioning of
the materiel.
(12) To assign duties when firing with reduced personnel..
(13) To conduct the fire of his piece on a moving target
when so ordered by the executive.
b. Detailed description of certain duties . — (1) To lay for
elevation when gunner's quadrant is used . — (a) The com-
mand quadrant (so much) indicates that the gunner’s quad-
rant is to be used.
(b) To set an elevation on the gunner’s quadrant, for ex-
ample, 361.8 mils, the chief of section sets the upper edge of
the head of the index arm opposite the 360 mark of the
graduated arc on the quadrant frame; he then slides the
slide level along the index arm until the index of the slide
level is opposite the 1.8 mark of the scale on the index arm.
In setting the slide, the chief of section must be careful to
use the scale on the index arm which is on the same side of
the quadrant as the graduated arc he used in setting the index
arm at 360 mils. After he has set the slide, he tightens the
clamp just enough to hold the slide in place.
(c) The announced elevation having been set on the gun-
ner’s quadrant, the piece loaded, and the breechblock closed,
the chief of section places the quadrant on the quadrant seat,
with the words “line of fire” at the bottom and the arrow
pointing toward the muzzle. The chief of section must be
sure to use the arrow which appears on the same side of the
quadrant as the scale which he is using. He stands squarely
opposite the side of the quadrant and holds it firmly on the
quadrant seat, parallel to the axis of the bore. It is important
that he take the same position and hold the quadrant in the
same manner for each subsequent setting, so that in each case
he will view the quadrant bubble from the same angle.
( d ) No. 1 operates the elevating handwheel until the quad-
rant bubble is centered, making sure that the last movement
is in the direction in which it is most difficult to turn the
handwheel. The chief of section warns No. 1 when the
bubble is approaching the center, in order that the final
centering may be performed accurately.
(2) To measure elevation (range) . — At the command
measure the elevation (range), the piece having been laid,
18
105 -MM HOWITZER M2
20
the chief of section causes No. 1 to set site 300 and, with
the elevating knob, to level the range quadrant elevating
bubble. The chief of section then reads the elevation (range)
set on the elevation scale (range drum) and announces the
elevation (range) thus set; for example, “Elevation (range)
No. (so-and-so) , (so much)
(3) To measure minimum quadrant elevation or minimum
elevation ( range ) . — (a) Quadrant elevation. — The command
is: MEASURE THE MINIMUM QUADRANT ELEVATION.
The chief of section, sighting along the lowest element of the
bore, causes No. 1 to operate the elevating mechanism until
the line of sight just clears the crest. He then measures
the quadrant elevation and, after reading the angle on the
quadrant, reports it to the executive thus: “Minimum quad-
rant elevation No. (so-and-so) , (so much) .”
(b) Elevation . — The command is: MEASURE THE MINI-
MUM ELEVATION, SITE (SO MUCH) .—The chief of section
causes No. 1 to set the site announced. Then, sighting along
the lowest element of the bore, he causes No. 1 to operate
the elevating handwheel until the line of sight just clears
the crest. No. 1 then levels the bubble of the range quadrant
by turning the elevating knob. The chief of section reads
the elevation setting and reports it to the executive thus:
“Minimum elevation No. (so-and-so) , (so much) , site (so
much)
(c) Range. — The command is: MEASURE THE MINIMUM
RANGE, CHARGE (SO-AND-SO) , SITE (SO MUCH) . The
chief of section causes No. 1 to install the range drum for
the announced charge, and to set the site announced. Then,
sighting along the lowest element of the bore, he causes No.
1 to operate the elevating handwheel until the line of sight
just clears the crest. No. 1 then levels the bubble of the
range quadrant by turning the elevating knob. The chief
of section reads the range setting and reports it to the execu-
tive thus: “Minimum range, No. (so-and-so), (so much),
charge (so-and-so), site (so much).”
id) When the executive announces the minimum quadrant
elevation or the minimum elevation (range), charge, and
site, the chief of section records it in a notebook and causes
the gunner to chalk it on a convenient place on the carriage.
(4) To indicate to gunner the aiming point , referring point,
or target. — Whenever an aiming point, a referring point, or
19
20
FIELD ARTILLERY
a target has been designated by the executive, the chief of
section will make sure that he has properly identified the
point in question. He will then indicate it to the gunner. If
there is any possibility of misunderstanding, the chief of
section will turn the telescope until the horizontal and vertical
hairs are on the point designated.
(5) To follow fire commands . — The chief of section will fol-
low the fire commands mentally. He will not repeat the
commands, but will be prepared to give any element of the last
command to any cannoneer who has failed to hear it.
(6) To indicate when piece is ready to fire . — When the ex-
ecutive can see arm signals of the chief of section, the chief
of section will extend his right arm vertically as a signal
that the piece is ready to fire. He gives the signal as soon
as the gunner calls “Ready.” When arm signals cannot be
seen, the chief of section reports orally to the executive,
“No. (so-and-so) ready.”
(7) To give command to fire . — When No. 1 can see arm sig-
nals made by the chief of section, the chief of section will give
the command to fire by dropping his right arm sharply to
his side. When his arm signals cannot be seen, he orally
commands: NO. (SO-AND-SO) FIRE. The chief of section
will not give the signal or command to fire until all the can-
noneers are in their proper places. He will require the can-
noneers to stand clear of the piece for the first round.
(8) To report errors and other unusual incidents of fire
to executive . — If for any reason the piece cannot be fired,
the chief of section will promptly report that fact to the
executive, and the reason therefor; for example, “No. (so-and-
so) out, misfire.” Whenever it is discovered that the piece
has been fired with an error in laying, the chief of section
will report that fact at once; for example, “No. (so-and-so)
fired with incorrect deflection.” Whenever the gunner re-
ports that the aiming posts are out of alinement with the
telescope, the chief of section will report that fact and request
instructions. Likewise, he promptly reports other unusual
incidents that affect the service of the piece. (See par. 33.)
(9) To conduct prearranged fire schedules . — Whenever the
execution of prearranged fire schedules is ordered, the chief
of section will conduct the fire of his section in strict con-
formity to the schedule prescribed.
(10) To record basic data . — The chief of section will record
20
105-MM HOWITZER M2
20
in a notebook data of a semipermanent nature. These in-
clude such data as minimum elevations; base deflections, in-
cluding aiming points used; prearranged fires when prepared
schedules are not furnished; safety limits in elevation and
deflection; number of rounds fired, with the date and hour;
and calibration corrections when appropriate.
(11) To observe and check functioning of materiel. — The
chief of section closely observes the functioning of all parts
of the materiel during firing. Before the piece is fired, he
verifies the fact that the recoil mechanism contains the
proper amount of oil; thereafter he carefully observes the
functioning of the recoil system. He promptly reports to the
executive any evidence of trouble (par. 46) .
(12) To assign duties when firing with reduced personnel . —
Whenever the personnel of the section serving the piece is
temporarily reduced in numbers below that indicated in this
manual, the chief of section will make such redistribution of
duties as will best facilitate the service of the piece.
(13) During direct laying cm moving target , to conduct fire
of his piece when so ordered by executive. — (a) Initial lead . —
The chief of section observes the target, estimates its lateral
speed, and (based on the speed) estimates the lead in target
lengths.
(b) Initial range or elevation . — The chief of section esti-
mates the initial range to the target and announces the
range or the corresponding elevation. The announced range
is used by the gunner when he lays for range (par. 21b (8) )
and by No. 1 when he lays for range using the elbow telescope
(par. 22b(2) (b) ) . The announced elevation is used by No. 1
in laying for elevation (par. 22b(3)(b)). The chief of sec-
tion announces the elevation which is the algebraic sum of
the range elevation and angle of site. For rapid determina-
tion of the elevation he should be furnished with a tabulated
card for Charge VII, showing the elevation setting for plus
and minus angles of site and ranges for which such fire may
be used. He is trained to determine the range and measure
the site to various points in the sector from which enemy
combat vehicles may be expected to appear. These are
recorded and should be memorized by him. They are used
in determining the initial elevation announced.
(c) To announce an initial range {elevation) and lead . —
The command is: TARGET (SO-AND-SO), RANGE (EXJE-
426841°— 41-
4
21
20-21
FIELD ARTILLERY
VATTON) (SO MUCH), LEAD (SO MANY) TARGET
LENGTHS.
( d ) To announce a change in range ( elevation ) and lead . —
The chief of section observes the fire of his piece, and when
the gunner or No. 1 is not tracking the target effectively, he
announces a range change or a new lead. The announced
change in range or elevation is given in yards. The command
is: UP (DOWN) (SO MUCH). The announced change in
lead is given as a new lead in the number of target lengths.
The command is: LEAD (SO MANY).
H 21. Gunner. — a. Enumeration of duties . — (1) (a) To center
the bubbles on the telescope mount.
(b) To set or change the deflection.
(c) To apply the deflection difference.
id) To lay for direction.
(e) To call “Ready.”
(/) To refer the piece.
( g ) To record base deflection.
ih) To measure a deflection.
(0 To take and maintain an announced lead during direct
laying on a moving target,
( j ) When directed, to lay for range as well as direction,
during direct laying on a moving target.
( k ) To give the command to fire during direct laying on
a moving target.
(2) For indirect laying or direct laying on a stationary
target, the gunner performs the duties prescribed in (1) (a) ,
(b) , (c) , (d) , and (e) above.
(3) For direct laying on a moving target, the gunner per-
forms the duties prescribed in (l)(a), (z), and (A:) and,
when directed, in (?) above.
(4) When directed, the gunner performs the duties
prescribed in (1)(/), ( g ) and ( h ) above.
b. Detailed description of certain duties. — (l)To set or
change deflection . — (a) T6 set deflection. — At the command,
for example, deflection, i,885, the gunner first sets the
zero of the azimuth micrometer opposite the fixed index, if
it is not already so set. He then pushes the throw-out lever
and turns the rotating head until the hundreds' graduation
(18 in this case) is opposite the azimuth-scale index. He
then releases the throw-out lever and, grasping the deflection
22
105 -MM HOWITZER M2
21
knob with his left hand, with the thumb on top, turns the
knob to the left until the micrometer index is opposite the
graduation 85 of the counterclockwise graduations on the
azimuth micrometer. The line of sight will then make a
horizontal angle of 1,885 mils with the axis of the bore. He
then turns the azimuth micrometer until its zero graduation
is opposite the micrometer index. Any movement of the
azimuth micrometer does not change a deflection previously
set.
(b) To change deflection . — The gunner should be trained
always to grasp the deflection knob with his left thumb on
top, as then the command for changing the deflection will
indicate the .direction in which he should move his thumb in
turning the knob. He also should be taught that turning
the knob to the right decreases the deflection set on the
telescope and results in moving the muzzle to the right when
the piece is laid with the new deflection. Similarly, he should
be taught that turning the knob to the left increases the
deflection and results in moving the muzzle to the left when
the piece is laid. The deflection having been set at 1,885
mils, if a subsequent command is given, for example, right 65,
the gunner turns the deflection knob by moving his thumb to
the right until the micrometer index has moved from zero
to 65 on the clockwise graduations of the azimuth microm-
eter. As turning the deflection knob to the right decreases
the deflection, the resulting deflection will be 1,820 mils.
The azimuth micrometer is then reset with its zero opposite
the micrometer index. Should the command be left (so
much), the gunner changes the deflection setting in the
same manner, except that he moves his thumb to the left
and follows the counterclockwise graduations of the azimuth
micrometer.
(2) To apply deflection difference. — (a) The command is:
ON NO. (SO-AND-SO) OPEN (CLOSE) (SO MUCH) . The
gunner of the piece indicated in the command does not
change the deflection set on his telescope. Each of the other
gunners changes his deflection setting by the number of mils
specified in the command if his piece is next in line to the
piece indicated; by twice this number of mils if his piece is
second in line from the piece indicated; by three times this
number of mils if his piece is third in line from the piece
indicated.
23
21
FIELD ARTILLERY
(b) If the command is, for example, on no. i open 5 , the
gunner on No. 1 makes no change; the gunner on No. 2
turns the deflection knob by moving his thumb to the left
(away from the piece indicated in the command) , and sets
off 5 mils once; the gunner on No. 3 turns the deflection knob
in the same manner, and sets off 5 mils twice, or a total of
10 mils; the gunner on No. 4 turns his deflection knob in
the same manner, and sets off 5 mils three times, or a total
of 15 mils. It is recommended that gunners be taught to
use the telescope as an adding machine, instead of totaling
the shifts.
(c) Should the command be, for example, on no. 3 close 10,
the gunner on No. 1 turns the deflection knob by moving
his thumb to the left (toward the piece indicated in the
command), and sets off 10 mils twice, or a total of 20 mils;
the gunner on No. 2 turns his deflection knob in the same
manner, and sets off 10 mils once; the gunner on No. 3
makes no change; the gunner on No. 4 turns his deflection
knob by moving his thumb to the right and sets off 10 mils
once.
( d ) It should be noted that in making the deflection
changes involved in applying the deflection difference, each
gunner turns the deflection knob by moving his thumb away
from the piece indicated if the command is open, and toward
the piece indicated if the command is close; also that the
muzzles of the pieces will be moved in similar directions when
the pieces are laid after the deflection differences have been
set.
(e) When a deflection change and a deflection difference
are announced at the same time, for example, right 30, on
no. 1 close 5, both of which affect the gunner's piece, he
should first set off the deflection change and then apply the
deflection difference.
(/) In the methods described above, it is implied that the
gunner resets the azimuth micrometer with its zero opposite
the micrometer index each time the deflection knob has been
turned. If he does so, he starts each change in the deflection
setting with the micrometer index at zero. This facilitates
setting off the tens and units on the azimuth-micrometer
scales. It is important that the gunner, before turning the
deflection knob, verify the setting of the azimuth micrometer
24
105 -MM HOWITZER M2
21
to make sure that its zero coincides with the micrometer
index,
(3) To lay for direction. — (a) Indirect laying. — The de-
flection having been set, the gunner brings the vertical hair
of the panoramic telescope on the aiming point by traversing
the piece. If the amount of movement necessary is greater
than can be obtained by traversing, the trails must be shifted.
To have the trails shifted, the gunner commands or signals:
MUZZLE RIGHT (LEFT). No. 2 and No. 6 on the left trail
handspike and No. 3 and No. 7 on the drawbar on the right
trail then shift the trails so that the muzzle moves in the in-
dicated direction. They stop shifting when commanded or
signaled to stop by the gunner. The gunner then completes
the laying by bringing the vertical hair of the telescope on
the aiming point.
(b) Direct laying on stationary target. — The deflection hav-
ing been set, the gunner traverses the piece by means of the
traversing handwheel until the vertical hair of the telescope is
on his part of the target. If the amount of movement neces-
sary to lay on the target is greater than can be obtained by
traversing, the trails must be shifted ((a) above).
(c) Direct laying on moving target , — See (8) below.
( d ) Procedure to insure accuracy . — To take up lost motion,
the final movement of the traversing handwheel should be
such as to cause the vertical hair of the telescope to approach
the aiming point from the left. The gunner should habitually
lay with the vertical hair of the telescope on exactly the
same portion of the aiming point or target and insure that
the cross-level bubble is centered for each round.
(4) To call “Ready.” — The piece having been laid for direc-
tion, and No. 1 having called “Set,” the gunner verifies the
laying, moves his head clear of the telescope, and calls
“Ready” to indicate that the piece is ready to be fired.
(5) To refer piece. — The piece having been laid for direc-
tion, to refer the piece, the command is: 1 . aiming point
(so-and-so), 2. REFER. Without disturbing the laying of the
piece, the gunner brings the vertical hair of the telescope on
the new aiming point (referring point). He then reads and
announces the deflection thus set. Two referring points or-
dinarily are used, one for day and the other for night, A re-
ferring point should be at least 50 yards from the telescope.
Frequently the aiming posts will have to be used as referring
25
21-22
FIELD ARTILLERY
points, particularly at night. The chief of section records the
deflection and a description of each referring point in his
notebook. The gunner records the deflection and referring
point in current use on a convenient part of the carriage.
(6) To record base deflection. — At the command record base
deflection, the gunner records the deflection set on his tele-
scope upon some convenient part of the carriage or upon a
data board (par. 40) .
(7) To measure a deflection. — The command is: 1. aiming
point (so-and-so), 2. MEASURE THE DEFLECTION. The
piece having been established in direction, the gunner turns
the telescope until the vertical hair is on the aiming point. He
then reads and announces the deflection.
(8) For direct laying on moving target , to take and main-
tain an announced lead. — The command is: TARGET (SO-
AND-SO), RANGE (SO MUCH), LEAD (SO MANY) TAR-
GET LENGTHS. The gunner sets his azimuth scale at zero
and tracks the target with the traversing handwheel, keeping
the vertical hair of the telescope ahead of the target by meas-
uring the announced lead on the reticle scale. When time
does not permit the chief of section to announce the lead, it is
determined by the gunner.
(9) To lay for both direction and range on moving target . —
When required by the situation, the gunner will lay for both
direction and range on a moving target. He sets scales of
the rotating head of the telescope and the azimuth scale at
zero. He brings into coincidence the arrows indicating the
position of the telescope mount which brings the line of sight-
ing parallel to the axis of the bore. He then tracks the target
with the traversing and elevating handwheels, keeping the
vertical hair of the telescope ahead of the target by measur-
ing the announced lead on the reticle scale, and placing the
corresponding range line of the announced range on the base
of the target. He gives the command fire when he is laid.
When time does not permit the chief of section to announce
the range and lead, the gunner determines them.
■ 22. No. 1. — a. Enumeration of duties. — (1) (a) To set the
angle of site.
(b) To set the range.
(c) To set the elevation.
(d) To lay for elevation (range).
26
105-MM HOWITZER M2
22
(e) Tc open and close the breech.
(/) To call “Set.”
(g) To fire the piece.
( h ) To use the rammer.
(2) For indirect laying or direct laying on a stationary
target, No. 1 performs all of the duties prescribed in (1) above.
(3) For direct laying on a moving target, No. 1 performs
the duties prescribed in (1) above, except that when the
gunner lays for range as well as direction, No. 1 performs only
the duties prescribed in (1) (e) , (/) , ( g ) , and ( h ) .
b. Detailed description of certain duties . — (1) To set angle
of site. — No. 1 is first taught to read angles of site on the
angle-of-site scale and then to set angles of site. To set
an angle of site, No. 1 turns the angle-of-site knob until the
announced site is shown. The angle of site is indicated by
a scale graduated in hundreds of mils from 0 to 6 and a
micrometer scale graduated in mils. A site of 300 is horizon-
tal. No. 1 first sets the index in the proper section of the
scale in hundreds of mils and then sets the units on the
micrometer scale. The last motion in setting the angle of
site should be in the direction of increasing site.
(2) To set range. — (a) Using range drum. — No. 1 is first
taught to read ranges on the range drum and then to set
ranges. To set the range, No. 1 installs the range drum cor-
responding to the announced charge; he then turns the ele-
vating knob until the announced range is opposite the index,
making sure that the last movement is in the direction of
increasing range.
C b) Using elbow telescope. — In direct laying, when so di-
rected, he sets the range (with the correct angle of site auto-
matically applied) by using the appropriate range line in
the reticule of the elbow telescope. No. 1, using the elevat-
ing handwheel, keeps the range line corresponding to the
announced range on the base of the target.
(3) To set elevation. — (a) Indirect laying. — No. 1 is first
taught to read elevations on the elevation scale and then
to set elevations. To set an elevation, No. 1 sets the angle of
site at 300 (or at an announced site) and sets the announced
elevation on the elevation scale. The elevation is indicated
by a scale graduated in hundreds of mils from minus 100 to
plus 1,200 and a micrometer scale graduated from zero to
100 mils. No, 1 grasps the elevating knob-and turns it until
27
22
FIELD ARTILLERY
the announced elevation is shown, making sure that the last
movement is in the direction of increasing elevation.
(b) Direct laying on moving targets. — At the command
TARGET (SO-AND-SO), ELEVATION (SO MITCH), LEAD (SO MANY)
target lengths. No. 1 sets the angle of site at 300 and the
announced elevation on the elevation scale ((a) above) and
then lays for elevation ((4) below). Announced changes in
elevation are given in yards, for example, down, so. No. 1
having been trained to know the effect in range resulting
from turning the elevating handwheel, follows the announced
range changes by this method, without further reference to
the initial elevation setting.
(4) To lay for elevation (range). — No. 1 turns the cross-
level knob and levels the cross -level bubble. Having per-
formed the duties described in (1) and (2) (a), or (3) above,
he turns the elevating handwheel and elevates or depresses
the piece until the elevation bubble is level, making sure
that the last movement is in the direction in which it is
most difficult to turn the handwheel.
(5) To open and close breech . — (a) To open breech . — No.
1 grasps the breech operating lever handle, pushes down on
the handle to release the catch, and draws it toward him
and to the rear, opening the breech.
(b) To close breech. — No. 1 grasps the operating handle
and pushes it forward and away from him until the breech
is closed and the latch is engaged.
(c) Fire on moving targets.
1. In fire on moving targets when the gunner lays for
range as well as direction, No. I performs the
duties prescribed in (a) and (b) above.
2. When No. 1 lays for range using the elbow tele-
scope, No. 5 opens and closes the breech and fires
the piece.
(6) To call “Set.” — No. 1 calls “Set” when the piece has
been loaded, the breech closed, and the piece laid for site
and elevation.
(7) To fire piece. — In indirect laying, at the chief of sec-
tion’s command, “No. (so-and-so) fire/’ or in direct laying
on a moving target when the gunner is laying for direction
and range, at the gunner’s command “Fire,” No. 1 grasps the
handle of the lanyard and pulls it away from the piece as
far as possible. . Under no circumstances will No. 1 grasp
28
105 -MM HOWITZER M2
22-23
the lanyard until the gunner calls “Ready.” When the chief
of section gives the command “Stand clear” (for the first
round) , No. 1 steps clear of the wheel and at the command
or signal, “Fire,” leans forward, grasps the handle of the
lanyard, and fires the piece. If the chief of section com-
mands “With the long lanyard/’ No. 1 attaches the long
lanyard to the short lanyard and fires as previously described.
In case of a misfire, the instructions contained in paragraph
38 will be followed.
(8) To use rammer . — The rammer (bore brush) will be
handled by No. 1 only. The rammer and rammer staff are
used to extract unfired rounds or cartridge cases which can-
not be ejected by the extractor. To extract a cartridge case,
No. 1 removes the rammer (bore brush) from the rammer
staff, inserts the rammer staff in the bore, and lightly taps
the bottom of the inside of the case until it is loosened and
can be pushed out of the chamber. No. 2, standing at the
breech, receives the cartridge case in both hands. To ex-
tract an unfired round, the procedure described in paragraph
37 will be followed.
H 23. No. 2. — a, Enumei'ation of duties . — (1) To load the
piece.
(2) In volley fire, to call out the number of the round.
(3) When necessary, to assist No. 6 in shifting the left
trail.
(4) To inspect the chamber and bore frequently to find
out whether there is any residue from the charge.
b. Detailed description of certain duties. — (1) To load
the piece . — To receive the round, No. 2 steps with his left foot
toward No. 4 and grasps the round with his right hand at
the base of the cartridge case and his left hand in front of
the rotating band. After resuming his position facing the
gunner, he inserts the round in the breech and pushes it
home with his right hand. He must use care, especially at
higher elevations, to avoid injuring his hand. When neces-
sary to insert his hand into the breech recess, to push the
round home, he should first close his fist. No. 2 will be par-
ticularly careful to avoid striking the fuze against any
portion of the piece. To prevent premature bursts caused
by fuzes in projectiles being struck by the piece in recoil, a
round to be loaded will be held well out of the path of the
recoil until the gun is again in battery (AR 750-10) .
29
23-24
FIELD ARTILLERY
(2) To call out the number of the round. — To insure that
the correct number of rounds is fired in volley fire, No. 2 calls
out the range and the number of the round as he loads the
piece, and, as he loads the last round, adds “Last round.” For
example, when two rounds are to be fired at 2,800, he calls
out, “2,800 two, last round.” He should not speak louder
than is necessary to insure his being heard by the members
of his own gun squad.
(3) When necessary , to assist No. 6 in shifting left trail . —
No. 2 assists No. 6 in shifting the left trail as directed by the
gunner. The command is: MUZZLE RIGHT (LEl^T) , and
the trail is shifted in the opposite direction so that the
muzzle is swung in the direction indicated. At the gunner’s
command or signal to stop shifting, Nos. 2 and 6 lower the
trail to the ground.
(4) To inspect chamber and bore frequently to find out
whether there is any residue from charge, — No. 2 will inspect
the chamber and bore frequently, particularly when firing
in the lower zones and at low elevations, to make certain that
no residue from the charge, which might cause jamming of
the round in loading, remains in the chamber or bore.
■ 24. No. 3. — a. Enumeration of duties. — (1) To make the
prescribed setting of impact fuzes.
(2) To set the fuze setter.
(3) To set time fuzes.
(4) When necessary, to assist No. 7 in shifting the right
trail.
b. Detailed description of certain duties. — (1) To make
prescribed setting of impact fuzes. — (a) The fire commands
for opening fire will contain a designation of the setting de-
sired, when the prescribed fuze can be given more than one
setting.
( b ) If the command is fuze quick, No. 3 will verify the
setting, and reset to “quick” any fuzes which may be set
“delay.”
(c) After firing is completed, No. 3 will reset to “quick” any
fuzes which have been set “delay.”
(2) To set fuze setter. — The duties of No. 3 in setting the
fuzes are as prescribed by the battery executive.
(3) To set time fuzes. — The duties of No. 3 in setting time
fuzes are as prescribed by the battery executive.
30
105 -MM HOWITZER M2
24-26
(4) When necessary , to assist No. 7 in shifting right
trail. — No. 3 assists No. 7 in shifting the right trail as di-
rected by the gunner. The command is: MUZZLE RIGHT
(LEFT) , and the trail is shifted in the opposite direction so
that the muzzle is swung in the direction indicated. At
the gunner’s command or signal to stop shifting, Nos. 3 and 7
lower the trail to the ground.
■ 25. No. 4. — a. Enumeration of duties. — (1) When directed
by the gunner, to lower the left top shield and lock it in
position.
(2) To assist No. 3 in setting time fuzes.
(3) To pass the round to No. 2.
b. Detailed description of certain duties . — (1) When di-
rected by gunner, to lower left top shield and lock it in
position. — When the fire commands are such as to require
an aiming point (referring point) to the front, No. 4, when
directed by the gunner, will promptly lower the left top
shield and lock it in the lowered position.
(2) To assist No. 3 in setting time fuzes. — See paragraph
24b (3).
(3) To pass round to No. 2. — No. 4 with his left hand
under the cartridge case, his right hand under the projectile,
taking care that the projectile and cartridge case do not
separate, so passes the round to No. 2 that No. 2 is able to
grasp the base of the cartridge case in his right hand.
■ 26. No. 5. — a. Enumeration of duties. — (1) To set out the
aiming posts.
(2) To prepare charges.
(3) To pass the round to No. 4.
(4) To open and close the breech and fire the piece when
those duties are not performed by No. 1.
b. Detailed description of certain duties. — (1) To set out
aiming posts. — When so directed by the chief of section, No. 5
sets out the aiming posts under the guidance of the gunner
(see par. 31) .
(2) To prepare charges. — The fire commands for opening
fire will include the designation of the charge. Unless Charge
VII is designated, No. 5, assisted by Nos. 6 and 7, removes the
projectile from the cartridge case, withdraws the increments
from the cartridge case, and removes those numbered higher
than the charge designated. He then replaces the remaining
31
26-28
FIELD ARTILLERY
increments in the cartridge case in their original numerical
order and reassembles the projectile to the cartridge case. To
disassemble the round, No. 7 grasps the cartridge case near the
neck and holds it in a vertical position ; No. 6 grasps the body
of the projectile and, with a twisting motion, lifts the projectile
clear of the cartridge case. After No. 5 has prepared the
charge, No. 6, assisted by No. 7, reassembles the projectile to
the cartridge case. Care must be used to prevent damage
to the lip of the cartridge case.
(3) To pass round to No. 4. — No. 5 will pass the round to
No. 4 in the most convenient manner.
(4) To open and close breech and fire piece when those
duties are not performed by No. 1 . — When No. 1 lays for range
with the elbow telescope or lays for elevation in direct laying
against moving targets, No. 5 will take position in rear of No. 1
and will open and close the breech and fire the piece (see par.
22b(5) and (7)).
E 27. No. 6. — a. Enumeration of duties. — (1) To remove am-
munition from containers.
(2) To assist No. 5 in preparing charges.
(3) When necessary, assisted by No. 2, to shift the left trail.
b. Detailed description of certain duties. — (1) To remove
ammunition from containers . — Assisted by No. 7, No. 6 re-
moves rounds from their containers and arranges them so
that they are within easy reach of No. 5. He inspects each
round to see that it is free from sand and dirt and that the
rotating band is not burred. With an oily cloth he wipes off
any foreign matter. Projectiles with burred rotating bands
should be placed aside until he can remove the burrs with
a file.
(2) To assist No. 5 in preparing charges. — When so directed,
No. 6 and No. 7 assist No. 5 in preparing charges as described
in paragraph 26b(2).
(3) When necessary , assisted by No. 2, to shift left trail. —
When so directed by the gunner, No. 6, assisted by No. 2, shifts
the left rail (see par. 23b(3)>.
■ 28. No. 7. — a. Enumeration of duties. — (1) To assist No. 6
in removing ammunition from containers.
(2) To assist No. 5 in preparing charges.
(3) To keep empty cartridge cases out of the way of the
cannoneers.
32
105 -MM HOWITZER M2
28-30
(4) When necessary, assisted by No. 3, to shift the right
trail.
b. Detailed description of certain duties . — (1) To assist
No, 6 in removing ammunition from containers . — No. 7 assists
No. 6 in removing rounds from their containers as described in
paragraph 27b(l).
(2) To assist No. 5 in preparing charges. — No. 7 and No. 6
assist No. 5 in preparing charges as described in paragraph
26b(2).
(3) To keep empty cartridge cases out of way of can-
noneers . — No. 7 piles the empty cartridge cases in rear of the
right trail' where they will be out of the way of the cannoneers.
(4) When necessary , assisted by No. 3, to shift right trail . —
When so directed by the gunner, No. 7, assisted by No. 3,
shifts the right trail (see par. 24b(4)).
Section VIII
ADDITIONAL INFORMATION ON THE SERVICE OF
THE PIECE
S 29. Accuracy in Laying. — Sighting and laying instruments,
fuze setters, and elevating and traversing mechanisms will be
so manipulated as to minimize the effects of lost motion. This
requires that last motions in setting instruments and in laying
be always in the directions prescribed. The gunner and any
other cannoneers who have duties in connection with laying
the piece will invariably be required to verify the laying after
the breech has been closed.
B 30. Fire at Will. — The piece being uncovered and pre-
pared for action, in case of sudden attack, when the target
appears at a range of less than 600 yards, the executive
may command: 1. target (so-and-so), 2. FIRE AT WILL. If
a method of close defense has been prearranged, the com-
mand is simply FIRE AT WILL. The chief of section repeats
the command adding the target designation (when neces-
sary) , the range or elevation, and the lead.
a. The methods of fire used in direct laying on moving
targets are —
(1) The gunner lays for direction. No. 1 lays for elevation
(algebraic sum of range elevation and site) . No. 5 opens and
closes the breech and fires the piece.
(2) The gunner lays for direction. No. 1 lays for range,
33
30-33
FIELD ARTILLERY
using the elbow telescope. No. 5 opens and closes the breech
and fires the piece.
(3) The gunner lays for both direction and range. No. 1
opens and closes the breech and fires the piece.
b. Firing is commenced at the gunner’s command fire.
The piece is loaded and fired as rapidly as possible until the
command cease firing, or until the enemy disappears from
view or actually reaches the piece.
■ 31. Aiming Posts. — When a suitable natural aiming post
is not visible, the piece, after it has been laid initially for
direction, is referred to the aiming posts as described in
paragraph 21M5). Two aiming posts are used for each
piece. Each post is equipped with a light for use in firing
at night. One post is set up in a convenient location at
least 100 yards from the piece. The other post is set up at
the midpoint between the first post and the piece, and is
lined in by the gunner so that the vertical hair of his tele-
scope and the two aiming posts are all in line. Any lateral
displacement of the piece during firing can then be detected
easily and corrected as indicated in paragraph 32. For
night use, the lights should be adjusted so that the far one
will appear several feet higher than the near one; thus the
two lights will clearly establish a vertical line on which the
vertical hair of the telescope can be laid.
■ 32. Displacement Correction. — a. When a gunner sees
that his aiming posts are out of line, he notifies the chief of
section (who notifies the executive) and uses the far post
for laying until the piece can be moved or a correction is
authorized by the executive. The correction is made by the
gunner, who —
(1) Lays on the far post.
(2) Refers to the near post.
(3) Lays on the far post with the new reading.
(4) Reports the new deflection.
(5) Realines the posts (as soon as practicable) by having
the near post moved.
b. Lateral displacement is most likely to occur when the
axle of the piece is not level.
■ 33. Reporting Errors. — All members of the howitzer squad
are trained to report to the chief of section errors in setting
34
1 0 5 -MM HOWITZER M2
33-37
or laying discovered after the command fire has been given.
The chief of section will immediately report errors to the
executive, as prescribed in paragraph 20b (8).
■ 34. Cease Firing. — The command cease firing normally is
given to the howitzer squad by the chief of section, but in
emergencies anyone present may give the command. At this
command, regardless of its source, firing will cease immedi-
ately. If the piece is loaded, the chief of section will report
that fact to the executive. Firing is resumed at the executive’s
announcement of the range or elevation.
■ 35. Suspend Firing. — The command suspend firing is
given only when the battery is firing on a prearranged sched-
ule and a temporary halt in the firing is desired. At this com-
mand, firing is stopped, but settings continue to be altered in
conformity with the schedule. If the piece is loaded, the chief
of section will report that fact to the executive. Firing will
be resumed at the executive’s command resume firing.
■ 36. Change in Data During Firing. — The announcement to
the gun squad of any new element of firing data serves as a
signal to stop all firing previously ordered but not yet ex-
ecuted. If the piece is not loaded when a new element of firing
data is announced, the new data will be set off and firing re-
sumed at the announcement of the range or elevation. If the
piece is loaded and the new data require a change in the fuze
setting, the chief of section will suspend firing and report to
the executive that the piece is loaded. The piece will be un-
loaded (par. 37) or firing will be resumed only on orders of
the executive. (If no change in the fuze setting is required,
the new data are set off and the firing is resumed.)
W 37. To Unload Piece. — a. When the command unload is
given, No. 1 opens the breech slowly. No. 2, standing at the
breech, receives the ejected round or cartridge case.
b. Should the extractor fail to eject the complete round,
the assembled staff and rammer (or staff and unloading de-
vice, if available) is used. An officer sees that the recess in
the head of the rammer or device is free from obstructions.
Under the direct supervision of an officer, No. 1 inserts the
rammer or device in the bore until the head encloses the fuze
and comes in contact with the projectile. He pushes and, if
35
37-40
FIELD ARTILLERY
necessary, taps the rammer staff lightly until the round is
dislodged from its seat. He then pushes it out of the breech;
No. 2 receives it.
e. If the extractor has ejected the cartridge case but not
the projectile, No. 1 fills the chamber with waste and closes
the breechblock. He dislodges the projectile as prescribed in b
above. No. 2 then opens the breech, removes the waste, and
receives the projectile as No. 1 pushes it to the rear.
d. When practicable, the procedure prescribed in TM
9-1900 should be followed.
■ 38. Misfires. — In the event of a misfire, at least three at-
tempts to fire the primer will be made. After at least 2
minutes have elapsed since the last attempt to fire the primer
the executive will command UNLOAD. The procedure is the
same as in paragraph 37a. If the extractor ejects the round,
the round will be disposed of as prescribed in TM 9-1900. If
the extractor ejects only the cartridge case (which will hap-
pen most frequently), the case will be immediately thrown
clear of all personnel to prevent injury in case of a hangfire.
Another cartridge case with the proper charge will be inserted
in the breech, care being taken not to damage the case.
Authority to fire the round will be obtained from the office]'
conducting fire.
BI 39. Ammunition. — Ammunition must be protected from
damage, especially the rotating bands and cartridge cases.
It is sorted and stored by lots. It is kept in containers as
long as practicable. Whether in or out of containers, it is
protected from dirt and ground moisture by being placed on
paulins or raised off the ground. It is protected from sun
and rain by a paulin or other shelter placed above it. The
powder temperature is kept uniform for any one lot; to permit
free circulation of air, wood or brush is placed between layers
of unboxed rounds. If time permits, trenches for ammunition
will be dug to minimize the effects of a direct hit. The
ammunition is stacked, with each stack containing not more
than 75 rounds and being not more than 4 layers high.
Stacks are at least 10 yards apart.
H 40. Section Data Board. — When positions are occupied for
more than a few hours, each chief of section should maintain
a section data board on which he records such items as base
36
105-MM HOWITZER M2 40-41
deflection, calibration corrections when appropriate, minimum
range or elevation, data for primary defensive fire missions,
and other data the need for which may be urgent.
Section IX
CARS AND MAINTENANCE OF MATERIEL
B 41. General. — a. This section covers such operations in the
care and maintenance of materiel as may be performed by a
battery in the field.
b. Complete instructions for battery maintenace, including
disassemblies, are found in the Technical Manuals and Stand-
ard Nomenclature Lists referred to in paragraph 2, especially
TM 9-325 and SNL C-21. Operations not covered in those
publications are performed by ordnance personnel.
c. In general, the battery is charged with preventive main-
tenance; that is, with routine cleaning, lubricating, and pre-
serving. Also, certain classes of repairs, adjustments, and
replacement of parts may be made under the direction of an
officer or the chief mechanic. Parts which may be drawn by
a battery for replacement purposes are indicated in SNL C-21
by the symbol %, and unless specifically prohibited, such parts
may be installed by the battery mechanic. For routine care
and maintenance, specific duties are assigned to individuals
or gun squads, and a strict accountability for the proper per-
formance of such duties is enforced.
d. The following operations may be performed within the
battery:
(1) Draining and replenishing the recoil liquid.
(2) Dismounting the howitzer from the sleigh.
(3) Dismounting the sleigh from the cradle.
(4) Removal, disassembly, and replacement of parts of the
breech, operating, and firing mechanisms.
(5) Removal of the equilibrator for cleaning and lubri-
cating.
(6) Removal, care, and maintenance of wheels, wheel bear-
ings, and tires.
(7) Maintenance and adjustment of the brake mechanism.
(8) Replacement of minor parts or assemblies indicated
by the symbol % in Standard Nomenclature List C-21.
37
42-43
FIELD ARTILLERY
H 42. Inspection.- — Regulations do not require that periodic
inspections of ordnance materiel be made by field artillery
troops. However, the battery executive should make a daily
general inspection and, following the monthly lubrication
period, he should make a detailed inspection of the materiel.
The purpose of the daily inspection is to insure that the bat-
tery is properly performing its preventive maintenance func-
tions. For this purpose, a general inspection of the weapon
for appearance and a spot check of one or two parts of the
weapon for mechanical functioning are deemed sufficient.
The parts selected for spot check should be varied from day
to day in order to insure a check of all parts of the weapon.
At the monthly inspection all personnel of the firing battery
should be present. The executive should make a thorough
mechanical inspection of all weapons and an inspection of
ordnance tools, spare parts, and equipment for condition and.
for completeness of the sets. The artillery mechanic should
accompany the executive at the mechanical inspection of the
weapons. All necessary repairs or adjustments which may
be performed by the mechanic should be accomplished; all
other necessary repairs or adjustments should be reported
to ordnance personnel. In addition to the two inspections
referred to above, there should be frequent inspections by
battery, battalion, and regimental commanders, at which
times the complete battery allowances should be displayed
and inspected. These command inspections insure, in general ,
only that the appearance and completeness of equipment are
maintained at the prescribed standard. General instructions
concerning the inspection of this materiel are found in section
VI, TM 9-325.
■ 43. Cleaning. — a. Dirt and grit accumulated in traveling
or from the blast of the piece in firing settle on the bearing
surfaces, and in combination with the lubricant form a cut-
ting compound. Primer fouling attracts moisture and has-
tens the formation of rust. During lulls in firing and imme-
diately after firing, the piece must be thoroughly cleaned.
At other times it should be cleaned at intervals not exceeding
2 weeks, depending upon the use and condition. Dirt on
nonbearing surfaces can usually be removed by water; lubri-
cated or other greasy parts must be cleaned with dry-clean-
ing solvent applied with a rag. The procedure in cleaning
38
10 5 -MM HOWITZER M2
43-44
the bore and breech mechanism is described in paragraphs
47 and 48. The following cleaning materials are issued by
the Ordnance Department for use in the field:
(1) Soda ash ( dehydrated sal soda). — Used for cleaning
the bore, breech mechanism, and firing mechanism after
firing.
(2) Dry-cleaning solvent . — For removing grease. It is
preferred to kerosene because it does not leave a corrosive
film, and to gasoline because it is less inflammable.
(3) Crocus cloth. — This is the coarsest abrasive permitted
for cleaning rust and stains from bearing surfaces.
(4) Emery cloth. — Used for cleaning unfinished or non-
bearing steel surfaces only. Issued in five degrees of coarse-
ness, of which 00 is the finest.
(5) Burlap , jute. — Issued for cleaning the bore.
(6) Cotton vxiste , clean rags, and sponges. — For general
cleaning purposes.
b. A division of duties for members of the gun squad in
routine cleaning and maintenance is as follows:
(1) Gunner . — Telescope, telescope mount, and gunner’s
quadrant.
(2) No. 1 . — Range quadrant, elbow telescope and mount,
and firing mechanism.
(3) No. 2. — Breech mechanism and firing lock.
(4) No. 3 . — Fuze setter.
(5) Nos. 4, 5, 6, and 7. — Bore, elevating and traversing
mechanisms, and recoil slides.
(6) Other cannoneers . — Assist in the operations as directed
by the chief of section.
■ 44. Lubrication. — a. To facilitate identification, all oil
holes and grease fittings should be marked with bright red
enamel.
b. Lubrication instructions for the gun and carriage are
covered in figure 6.
c. The following lubricants are issued by the Ordnance
Department for use on this materiel:
(1) Engine ( crankcase ) oil, SAE 10 (Navy contract symbol
1042). — A pure petroleum oil used for general purpose lubri-
cation when the temperature is below 32° F. When Navy
contract oil is unobtainable, use premium or regular brand
of first quality SAE 10 motor oil sold by reputable companies.
39
44
FIELD ARTILLERY
BORE ©
4 FITTINGS- CRADLE RECOIL SLIDES AND GROOVES ©
CRADLE LOCK BRACE ASSEMBLY AND LATCHES ©
1 FITTING-ELEVATING PINION 5HAFT ©
1 FITTING-AXLE SUPPORT PIVOT PIN ©
i FITTING- PINTLE BEARING. TOP ©
TOP SHIELD HINGES AND LOCK PINS ©
1 FITTING-AXLE SUPPORT LOCK, LEFT©
HAND BRAKE LEVER MOVING PARTS ©
WHEEL BEARINGS-HAND PACK BEARINGS ONLY ©
ELEVATING ARC AND PINION, LEFT ©
TRAVERSING WORM AND RACK ©
AXLE SUPPORT GIB BEARINGS, LEFT ©
1 FITTING-TRAVERSING HANDWHEEL SHAFT BEARINGS ©
TRAIL LOCK PIN ©
1 FITTING-TRAIL HINGE PIN ©
TRAVERSING HANDWHEEL HANDLE ©
3 FITTINGS-PAN. TELESCOPE MOUNT M2I©
1 FITTING- TRUNNION, LEFT ©
1 FITTING-PINTLE BEARING, LOWER ©
1 FITTING-LEFT ELEV. HANDWHEEL SHAFT BEARING ©
EXPOSED PORTION CRADLE SLIDES ©
TRAVELING LOCK SHAFT PIECE (BALL) ©
i OIL CUP-TRAIL LOCK LATCH ©
TRAIL LOCK HOOK AND LEVER PINS ©
* FOLLOW INSTRUCTIONS PRESCRIBED IN TM 9-325
OR IN PAR 47, FM 6-75
LUB
3ICANTS REQUIRED
TEMPERATE CONDITION
ARCTIC CONDITION
©
Oil. engine. SAE 10 for below 32°F
Oil. engine, SAE 30 for above 32°F
Oil,lubricotmg,for aircraft
instruments and machine guns
©■
Greose.OD. No.O
Greose.O.D. NoOO
BE
Grease, wheel bearing. No. 2
Grease .wheel bearing, No.2
Figure 6. — Lubrication chart,
(2) Engine ( crankcase ) oil , SAE 30 (Navy contract symbol
1065 or 3065). — An oil used for general lubricating purposes
as in (1) above, when the temperature is above 32° F.
(3) Grease , O. D. No. 0 (Treasury contract, TPS, class
14). — An automotive type of mineral grease. It is used in
the grease fittings of the howitzer in both summer and winter.
At least every 6 months all old grease is removed; the gear
boxes and housing are cleaned with dry-cleaning solvent,
wiped dry, and packed with new grease.
40
105 -MM HOWITZER M2
44-45
CRADLE RECOIL SLIDES AND GROOVES-^ FITTINGS
RECOIL INDICATOR
AXLE SUPPORT LOCK, RIGHT- l PITTING
TOP SHIELD HINGES AND LOCK PINS
HAND BRAKE LEVER MOVING PARTS
ELEV. ARC AND PINION, RIGHT
ELEVATING GEAR HOUSING - 1 FITTING
WHEEL BEARINGS - HAND PACK BEARINGS ONLY
AXLE SUPPORT GIB BEARING, RIGHT
TRAIL HINGE PIN - 1 FITTING
TRAIL LOCK PIN
RANGE QUADRANT M4-6 FITTINGS
ELBOW TELESCOPE MOUNT- 1 OIL CUP
RIGHT ELEV.GEAR SHAFT BEARINGS - 3 FITTINGS
ELEVATING HANDWHEEL HANDLE
TRUNNION, RIGHT-1 FITTING
EQU1LIBRAT0R FULCRUM-HAND PACK
BREECH AND FIRING MECHANISMS
FLEXIBLE JOINTS ELEV.MECH.
LANYARD SHAFT HOUSING -1 OIL CUP
LEFT ELEV- GEAR SHAFT BEARINGS- 2 FITTINGS
CRADLE TRAVELING LOCK - 1 FITTING
CRADLE SLIDES, EXPOSED PORTION
TRAVELING LOCK SHAFT PIECE (BALL)
EQUILI 8RAT0R SPRING ROD BEARINGS- HAND PACK
TRAIL LOCK LOOP AND PIN
TRAIL DRAWBAR LOCK-1 FITTING
TRAIL DRAWBAR BEARING - 2 FITTINGS
WHEN APPLIED
CD DAILY.
® WEEKLY.
y MONTHLY-
0 EVERY SIX MONTHS, AND AFTER
BEING IMMERSED IN WATER-
HOW APPLIED
A OILER
•w PRESSURE LUB-GUN
HAND
10 5 -mm howitzer, M2.
(4) Grease , wheel bearing , No. 2 (Treasury contract, TPS,
class 14). — A special grease containing soap. It has a stringy
consistency. It is used for the high-speed roller bearings in
the wheel hubs. It does not run when hot, but is soluble in
water; consequently, repacking is required after continued
immersion in water. Wheel hubs are not packed, as this may
permit grease to reach the brake mechanism.
■I 45. Protection Against Chemicals. — a. Whenever chemical
attacks are anticipated, all bright parts should be covered
41
45-46
FIELD ARTILLERY
with oil. After a gas attack, the oil is wiped off and fresh oil
applied. If mustard or other persistent gas is used, absorbent
objects may be deeply contaminated, and even hard surfaces
may be dangerous for from 6 to 8 days, if the chemical is not
neutralized. Bleaching powder or chloride of lime and a non-
corrosive decontaminating agent (a solution of either a light
tan or white powdery material in acetylene tetrachloride) are
standard. The noncorrosive agent will be used for the de-
contamination of weapons when corrosion or other serious
damage might result from the use of chloride of lime.
b. The noncorrosive decontaminating agent is sprayed on
with the hand-operated decontaminating apparatus. The
contaminated surfaces should be given a number of light ap-
plications of the spray at intervals of 15 to 30 minutes until
the required amount of solution has been applied (see BM
21-40). After all the solution has evaporated from the
treated surfaces, the materiel should be scrubbed, preferably
with soapy water, rinsed with clear water, and thoroughly
dried. When appropriate, metal surfaces should then be oiled
or greased to prevent corrosion.
c. Chloride of lime, if used, may be sprinkled on the mate-
riel, painted on as a whitewash, or sprayed on with the hand-
operated decontaminating apparatus. The application should
not be left on for more than an hour at most, after which the
lime is washed off and the materiel rinsed thoroughly with
Water.
d. All cleaning rags and sticks used in decontamination
must be destroyed or otherwise disposed of to prevent danger
from subsequent handling. If destroyed by burning, care
must be taken to prevent contamination by dangerous vapors
produced. If possible, the articles should be buried. In all
cleaning operations, the gas mask and special gasproof gloves
must be worn.
B 46. Recoil Mechanism. — a. General . — Battery mainte-
nance of the recoil mechanism is limited to exterior cleaning
and lubricating, draining and filling with recoil oil, remov-
ing the recoil cylinder rear head, and disconnecting the piston
rod from the cradle. Whenever the barrel is removed, the
recoil cylinder rear head should be removed in order to clean
the rear interior of the recoil cylinder and to inspect for ex-
cess oil leakage. At this time the rear head should be thor-
42
1 0 5 -MM HOWITZER M2 46
oughly cleaned and the relief valve should be lubricated and
checked for correct functioning. Only the heavy low-pour-
point recoil oil as issued by the Ordnance Department may be
used in the recoil mechanism. A full reserve of oil for the re-
coil system amounts to approximately IV 2 fills of the screw
filler. In using the screw filler, care must be exercised to pre-
vent crossing the threads or breaking off the end of the filler.
The screw handle must be turned with both hands. The
amount of oil reserve in the system is shown by the position of
the oil index with reference to the front face of the recupera-
tor cylinder front head, as follows:
(1) No reserve. — The indicator is well into the recess. The
piece must not be fired in this condition.
(2) Full reserve. — The end of the indicator is even with the
front face of the recuperator cylinder front head. The oil in-
dex does not of itself show when there is an excess of oil re-
serve, as the addition of excess oil does not move the index
out beyond the front face of the recuperator cylinder front
head. The piece must not be fired with an excess reserve (see
b below) .
b. Operations prior to firing. — (1) Before firing, the re-
serve oil should be extracted until an insufficient reserve is
indicated ; then a full reserve should be established by insert-
ing oil until the index is flush with the front face of the
recuperator cylinder front head.
(2) The rear end of the recoil cylinder, the filling- and-
drain-plug hole, and the oil index recess should be examined
for oil leakage. The presence of a few drops of oil at any of
these places is to be expected, but if there is an undue leakage
the piece must not be fired, and the condition should be
reported to ordnance personnel.
c. Operations during firing . — (1) During firing, the recoil
mechanism should be maintained at full reserve and the
slides kept clean and properly lubricated.
(2) The chief of section should constantly verify the com-
plete return of the piece to battery. Firing may be con-
tinued as long as the piece returns to battery sufficiently for
the firing mechanism to actuate the trigger shaft.
(3) The chief of section should constantly observe the be-
havior of the recoil mechanism in firing, and take such action
in the case of malfunctioning as is indicated below:
43
46
FIELD ARTILLERY
Malfunction
Cause
Correction
Oil index projects less
than the required dis-
tance.
(1) Loss of reserve oil.
(2) Loss of gas pres-
sure either through the
recuperator cylinder rear
head or past the floating
piston.
(1) Drain the remainder of
the oil reserve and refill to
normal.
(2) Gas escaping by the float-
ing piston is indicated by an
emulsified condition of the
reserve oil drained off. If in
reestablishing the oil reserve,
the oil index does not move out
and the oil screw filler works
easily , the gas pressure has been
lost. Substantiate this by an
attempt to drain the mechan-
ism. Oil will not spurt out
unless some pressure is present.
Report the malfunctioning to
ordnance personnel for repair.
Oil index remains sta-
tionary when the re-
serve is pumped in
against evident pres-
sure.
Failure of howitzer to
return to battery.
The packing is too
tight, or the index is
broken, or the index is
locked by some foreign
substance.
(1) Insufficient oil re-
serve.
(2) Dirt or obstruction
on the slides.
(3) Relief valve in re-
coil cylinder rear head
not functioning
(4) Low nitrogen pres-
sure, excessive internal
friction; damaged slides,
piston rod or piston.
Withdraw all reserve oil,
then insert approximately 1H
the capacity of the oil screw
filler. Tap the oil index
lightly as oil is being added.
If it still fails to function, re-
port the malfunctioning to
ordnance personnel for repair.
(In an emergency , drain all
reserve oil and insert fills
of the screw filler; the piece
then may be fired until the
howitzer returns to battery
with a shock when reserve oil
should be extracted, or the
howitzer fails to return to
battery when additional oil
should be inserted.)
(1) Withdraw the reserve oil
and establish a new full reserve.
(2) Clean and lubricate the
slides.
(3) Remove recoil cylinder
rear head and clean. If mal-
function continues, report the
malfunctioning to ordnance
personnel for repair.
(4) Report malfunction to
ordnance personnel for repair.
105-MM HOWITZER M2
46-47
Malfunction
Cause
Correction
Return of howitzer to
battery with a shock.
Too much oil reserve.
Withdraw reserve oil until
index is halfway in and, when
mechanism has cooled, refill
to a full reserve.
■ 47. Barrel Assembly and Slides. — a. Care of bore . —
Whenever the rate of firing permits, the bore should be
swabbed with clean water and a sponge; such swabbing should
be done at least once every hour during firing. During or just
prior to firing, it is unnecessary and undesirable to lubricate
the bore. Drying subsequent to swabbing should be insisted
upon. As soon as possible after firing, the bore is washed with
a solution of V 2 pound of soda ash (or 1 pound of sal soda) per
gallon of hot water. Cleaning of the bore is accomplished
by means of a swab of burlap around the metal end of the
rammer staff, or by means of the bore cleaning brush. No
attempt should be made to remove copper fouling. When
all powder fouling has been removed, the bore is swabbed
with clear water. Finally, it is dried with clean burlap or
cloths and then coated with engine oil, either SAE 10 or
SAE 30 depending upon the temperature. The cleaning
process may have to be repeated on successive days if there
is evidence of sweating. If the piece is not to be kept in
constant service, the bore should be slushed with rust-preven-
tive compound instead of oil. The chief purposes of swab-
bing the bore during the firing period are to flush out the
primer salts and residue and to lower the temperature of
the barrel. The purpose of cleaning after firing is to remove
all traces of the residue and primer salts that cause corro-
sion. A clean bore is indicated by a uniform grey appear-
ance; no attempts should be made to obtain a bright, polished
appearance since such attempts result in damage to the bore.
b. Care of slides . — The bronze slides should be examined
by retracting the howitzer until the rear of the breech is
opposite the rear of the cradle. Burs or rough spots are
removed with a fine file. The slides are cleaned with dry-
cleaning solvent, wiped dry, and coated with a light film of
engine oil. After the gun is secured in battery, engine oil
is applied to the slides through the eight oil fittings. Period-
45
47
FIELD ARTILLERY
ically, or at least every 2 weeks when in constant service, the
howitzer and sleigh should be removed from the cradle in
order to permit cleaning the entire length of the slides and
the interior of the cradle.
c. To retract howitzer. — The howitzer is retracted on its
slides as follows:
(1) Set the hand brakes.
(2) Place the howitzer at approximately zero elevation
and lash the elevating handwheel to the right shield brace.
(3) Remove the cotter pin and piston rod outer nut.
(4) Push the howitzer and sleigh to the rear, being careful
that the howitzer and sleigh are not pushed so far to the
rear that the breech ring bearing strips lose contact with the
rear of the cradle.
d. To remove howitzer and sleigh. — To prevent damaging
the recoil mechanism, first the howitzer is removed and then
the sleigh is removed. The procedure is as follows:
(1) Provide at least three heavy timbers and two rope
slings to support the howitzer in a horizontal position when
it is being removed.
(2) Set the hand brakes.
(3) Remove the breechblock.
(4) Place the howitzer at approximately zero elevation
and lash the elevating handwheel to the right shield brace.
(5) Remove the locking screw in the recoil mechanism
bracket locking ring (barrel locking ring) and remove the
ring.
(6) Start the howitzer to the rear by striking the muzzle
with one of the lifting timbers or by means of a pinch bar
inserted between the front of the breech ring and the rear
edge of the cradle trunnion bracket.
(7) Push the howitzer about 12 inches to the rear.
(8) Using timbers and a rope sling, support the breech
and muzzle ends of the howitzer to avoid cramping, and
carry the howitzer to the rear. The third timber and a rope
sling are used to support the middle of the howitzer as soon
as the front end passes within the sleigh. Place the howitzer
on wooden blocks or a suitable rest to prevent damage to the
finished surfaces and the bronze bearing strips in the bottom
face of the breech ring.
(9) Remove the cotter pin and piston rod outer nut.
46
105 -MM HOWITZER M2
47-48
(10) Four cannoneers working in pairs on opposite sides
of the carriage push the sleigh to the rear until it is free
from the cradle, then lift it off and place it on wooden blocks.
e. To replace howitzer and sleigh . — The howitzer and
sleigh are replaced by reversing the procedure of c or d above.
The piston rod outer nut should be fully tightened and then
backed off to the nearest castellation in order to permit side
play without noticeable end play; it must not be drawn so
tight that the inner nut is tight against the cradle. The
chief of section must verify before traveling and before firing
that the piston rod outer nut and its cotter pin are in place.
0 48. Breech and Firing Mechanisms. — a. General . — Since
the breech and firing mechanisms consist entirely of un-
painted and unprotected steel surfaces, the mechanisms are
subject to corrosion caused by powder fouling, rain, dirt, and
mud. It is of particular importance that the moving ele-
ments be kept well cleaned and lubricated. This can be
accomplished in only one way; that is, by a complete disas-
sembly of all moving parts. The solution of water and soda
ash (or sal soda) is used to remove the larger portion of the
fouling. After the parts are rinsed with clear water and
dried, any gummy residue remaining on them is removed
with dry-cleaning solvent. The mechanism is lubricated
while disassembled. It is important that the mechanism is
thoroughly cleaned and dried before being lubricated, that
the proper lubricant is selected, and that it is used in quan-
tities sufficient only to reduce friction. In case of doubt as
to the viscosity of oil to be used, especially when the piece
is to be fired, the lighter weight of oil should be selected.
Constant checking is necessary to insure that cracked parts
are replaced, and that burred parts are replaced or burs
removed. Hence, whenever the mechanism is disassembled,
each part should be carefully inspected.
b. Disassembly of breech mechanism and firing lock . —
To disassemble the breech mechanism —
(1) Raise the detent handle and remove the trigger shaft.
(2) Open the breech to the point where the assembling
line on the top of the operating lever is parallel with the side
of the breech ring and lift out the operating-lever pivot.
(3) Slide the breechblock to the right, removing the oper-
ating lever as soon as the crosshead clears the breech ring.
47
48
FIELD ARTILLERY
(4) Push the breechblock to the left to clear the extractor
and remove the extractor from the breech ring.
(5) Remove the breechblock by pushing through to the
right.
(6) Lay the breechblock on its lower face and remove the
detent spring retaining screw, spring, detent, and handle.
(7) Rotate the firing case 60° in either direction and pull
it out of the breechblock.
(8) Pry the trigger fork out of the firing case with a screw
driver, first through the trigger shaft hole, then from the
outside of the case.
(9) Insert the trigger shaft to engage the yoke ends of the
sear. Press the front end of the sear out of engagement with
the firing-pin holder, insert a screw driver through the bottom
hole and in rear of the firing-pin holder, and pry the assem-
bled sleeve and holder forward until they can be grasped and
pulled from the case.
(10) Remove the trigger shaft and shake out the sear and
sear spring.
(11) Hold the front end of the firing-pin holder in one
hand and place the lower rear end of the sleeve against the
edge of a bench or some convenient part of the carriage.
Push the firing-pin holder down to unhook it from the sleeve.
Allow the holder to recede out of the sleeve, freeing the spring.
(12) Remove the cotter pin from the firing-pin holder, un-
screw the firing-pin bushing, and remove the firing pin from
the bushing.
(13) Unscrew the cross-head screw and remove the cross
head.
c. Assembly of breech and firing mechanisms . — The breech
and firing mechanisms are assembled in the reverse order of
the disassembly described in b above. However, the following
aids and precautions should be observed.
(1) The ends of the cotter pin in the firing-pin holder
must be spread so that they will not rub the firing case.
(2) The sear spring may be readily inserted into its seat
by introducing the point of a screw driver between two coils
to hold the spring.
(3) The sear should be pressed down when the firing-pin
holder is inserted in the case. This is easily done by insert-
ing a screw driver through the front top hole of the firing
case.
48
105-MM HOWITZER M2
48-49
(4) The part of the trigger fork marked “muzzle face” must
be toward the front of the case when assembling.
(5) The trigger shaft may be inserted when the lines on
the firing case and the breechblock marked “top” coincide.
d. The causes and corrections of malfunctioning of the
breech and firing mechanisms are given in the following table :
Malfunction
Cause
Correction
Fails to fire; no percus-
sion on primer.
(1) Broken firing ,
spring; broken or de-
formed firing pin.
(2) Breechblock not
fully closed.
(3) Howitzer out of
battery.
(1) Disassemble firing lock
and replace broken or deformed
part.
(2) Close breechblock.
(3) Check recoil mechanism
for proper reserve and howitzer
slides for dirt or obstructions.
If cause is not found, report
malfunctioning to ordnance
personnel for repair.
Fails to fire until primer
is struck several times.
(1) Firing mechanism
parts not working freely.
(2) Weak firing spring.
(1) Disassemble firing lock
and examine for burs and
roughened surfaces. Remove
burs, and smooth roughened
surface with crocus cloth or an
oilstone. Wash parts with
dry-cleaning solvent, dry and
lubricate before reassembly.
(2) Replace.
Fails to fire when proper
percussion on primer
is obtained (misfire).
Defective primer.
Make three attempts to fire
the primer, then wait 2 minutes
before opening breech and re-
moving round. (See par. 38.)
Fails to extract empty
case.
Broken extractor.
Gently ram out the case.
Examine the edge of the cham-
ber for deformations or burs
which might cause difficult ex-
traction. Replace extractor.
■ 49. Equilibrator. — a. General . — To clean and lubricate the
equilibrator spring rod bearing and fulcrum bearing, the
equilibrator assembly should be dismounted from the car-
riage once a month. After the equilibrator is removed, the
bearings are washed in dry cleaning solvent, dried, and hand
packed with grease, O. D. No. 0. Disassembly of the equi-
49
49-51
FIELD ARTILLERY
librator is prohibited. There are no means provided for
adjusting the equilibrator.
b. To remove . — The equilibrator is removed as follows:
(1) Depress the piece to approximately zero elevation,
insert a 3- by 3- by 12-inch wood block between the front
spring seat and equilibrator fulcrum, and elevate the piece to
remove the load from the springs.
(2) Remove the cotter pins, and force out the headless
pins from the equilibrator fulcrum. Depress the piece, low-
ering the front end of the equilibrator to the ground. Pro-
tect it from the dirt.
(3) Drive out the straight pin from the traveling lock
(ball) piece on the right side of the cradle.
(4) Unscrew the ball piece.
(5) Gently push the traveling lock shaft to the left, hold-
ing the equilibrator to prevent its falling, and remove the
equilibrator assembly.
c. To mount . — Reverse the procedure of b above, noting
that the dust shields on either side of the equilibrator ful-
crum bearing are in place.
H 50. Elevating Mechanism and Cradle Trunnion Bear-
ings. — Disassembly, cleaning, and inspection of the elevating
mechanism and cradle trunnion bearings, and packing of
the elevating mechanism gear housings will be done at the
regular ordnance inspections.
■ 51. Wheels and Wheel Bearings. — a. General. — (1) The
care and maintenance of the wheel mechanism, including
tires, is a function of the battery. Tire pressure should be
maintained at 40 pounds. Tires should be removed at least
once a year and the disk and rim cleaned and painted. Every
6 months, or oftener if necessary, the wheel hubs should be
removed, the old grease flushed out, new grease pressed by
hand into the space between the cleaned and dried rollers
and: race, and the wheel bearings adjusted. Best results are
obtained if, after drying and before repacking, the roller
bearing is dipped into engine oil. Improper adjustment of
the roller bearings will cause the rollers to be pitted or
chipped. In general, a bearing chipped at the larger end
indicates that the adjustment was too tight; a bearing
chipped at the smaller end indicates too loose an adjustment.
50
105 -MM HOWITZER M2
51
At all halts during marches, the chiefs of section or a desig-
nated cannoneer should feel the wheel hubs for overheating.
(2) Overheating may be an indication of a tight bearing,
faulty lubrication, or a dragging brake. The cause must be
determined and correction made as directed by the officer in
charge.
b . Disassembly . — To disassemble the wheel hub from the
spindle —
(1) Remove the hub cap.
(2) Remove the cotter pin, castellated nut, and washer
from the spindle.
(3) Pull the hub from the spindle, being careful to pre-
vent the outer roller bearing from falling to the ground.
c. Assembly and adjustment . — To assemble the wheel hub
on the spindle and to adjust the wheel bearings —
(1) Clean and dry the bearings, dip the bearings in engine
oil, and fully pack with wheel-bearing grease. See that the
inner bearing is properly in place; the oil retainer must not
bear against the roller bearing. The hub cavity must not be
packed.
(2) Slide the wheel hub over the spindle, guiding the cup
of the inner roller bearing over the cone and rollers and the
brake drum over the brake shoe.
(3) Slide the outer cone and roller on the spindle, and
press it firmly into its seat in the hub.
(4) Install the washer and nut, and adjust the bearing.
To make this adjustment, the wheel should be rotated as the
adjusting nut is being tightened. It is best to rotate the
wheel in both directions, drawing up the nut until all the
bearing parts are firmly seated. At this point a drag or re-
sistance to rotation will be noted on the wheel. The nut
should now be backed off from one-sixth to one-quarter of
a turn. Now the wheel should rotate freely but without any
perceptible shake.
(5) Test the bearing adjustment by placing a short bar
between the tire and the ground, at the same time holding
one finger on the cage of the outer bearing. When, in work-
ing the bar up and down, a barely perceptible movement is
felt and the wheel rotates freely when given a slight spin,
the adjustment is correct. Insert the cotter pin and attach
the hub cap.
51
52
FIELD ARTILLERY
■ 52. Brake Mechanism. — a. General . — This weapon is
equipped with hand brakes for use during firing or while
the piece is being moved by hand, and with commercial
Warner electric brakes, for use during travel. Periodic test-
ing of both the hand and electric brake mechanisms is neces-
sary. No adjustment of the brake shoes is provided.
b . Hand brakes . — If the hand brake mechanism fails to hold
the weapon, the brake shoes may be replaced or the brake
lever may be removed from its splined shaft and rotated
enough to enable the brakes to hold. The hand-brake levers
should not be rotated so far that they will affect the opera-
tion of the electric brakes.
c. Electric brakes .• — When testing the brake mechanism the
procedures and precautions of TM 9-325 should be observed.
The causes and corrections of malfunctioning of the electric
brakes are given in the following table:
Malfunction
Cause
Correction
No brakes
(1) Broken wire in cir-
(1) Check wiring and repair
cuit.
broken wires.
(2) Controller defective.
(Test controller by con-
necting both wires to one
terminal and checking
brake operation.)
(2) Replace controller.
(3) Poor connection
(3) Check, clean, and tighten
all connections at brake, con-
troller load control, and socket.
(4) Broken wire or mag-
(4) If broken wire is on out-
net.
side of magnet, repair if pos-
sible. If no current flows
through magnet, replace with
new magnet.
(6) Poor ground connec-
(5) Clean and tighten con
tion in circuit.
nections.
(6) Defective plug or
(6) Check plug and socket
socket.
for loose connections, dirty or
corroded blades, or a broken
socket. Repair or replace with
new socket.
Very weak brakes
(1) Worn-out brake
(1) Replace brake band as-
lining.
sembly.
(2) Glazed magnet fac-
(2) Roughen with emery
ing.
cloth.
52
105 -MM HOWITZER M2
52-53
Malfunction
Cause
Correction
(3) Stop lights connected
(3) Remove stop lights from
in brake circuit.
(Changes the graduation
of the current as it passes
through the controller, re-
sulting in weak or grab-
bing brakes.)
brake circuit.
(4) Insufficient current.
(4) Insufficient current may
be due to poor connections at
the brake, controller and load
control ground, or the plug and
socket. Clean and tighten all
connections; check plug and
socket for corroded or dirty
blades.
(5) Poor ground connec-
(5) Clean and tighten con-
tion at the brakes.
tacts at the brake and frame.
(6) Controller burned
(6) Replace with new con-
out.
troller.
(7) Contactor arm in
(7) Smooth out contactor
the controller is pitted.
arm with fine emery cloth.
(8) Broken magnet
spring.
(8) Replace with new spring.
(9) Worn wheel bearings.
(9) Replace bearings.
■ 53. Sighting and Fire-Control Equipment. — a. General . —
Especial care is required to insure the positive and accurate
functioning of the sighting and fire-control mechanisms.
Care must be exercised to prevent denting the soft metal sur-
faces or scratching the lenses. The steel surfaces should be
kept covered with a light film of high-grade lubricant to pre-
vent corrosion. Dirt should be removed from optical surfaces
by brushing lightly with a camel’s hair brush. Oil or grease
should be removed from glass by applying alcohol or, if alco-
hol is not available, by breathing on the glass and then wip-
ing lightly with lens paper or a clean, soft cloth. Battery
personnel are forbidden to disassemble any part of the gun-
ner’s quadrant, panoramic or elbow telescopes, telescope
mounts, or range quadrant, but are permitted to perform
certain adjustments. The procedures of c to / below may be
used to insure accuracy of the sighting and laying mecha-
nisms. In general, the sighting system is correct —
(1) In direction , if the deflection scales read zero when
53
53
FIELD ARTILLERY
the line of sighting is in a plane parallel to the vertical plane
passing through the axis of the bore.
(2) In elevation —
(a) If, with the elevation scales of the panoramic tele-
scope set at zero and with the elevation indexes of the mount
in coincidence, the line of sighting through the zero range
line of the telescope is parallel to the axis of the bore.
(b) If the algebraic sum of the “site” and “elevation” setting
indicates the same angle above the horizontal that is meas-
ured with an accurate gunner’s quadrant on the tube.
(3) If there is no excessive lost motion between the sights
and the tube.
b. Testing equipment — Equipment used in testing sights
consists of bore sights and a gunner’s quadrant. Tools needed
for adjustments are a screw driver and a teat-wrench. The
target for bore sighting may be a terrain object more than
1,000 yards away, or a test target. When the test target is
used, the displacement of the axis of sighting from the axis
of the bore must be correctly shown. For this howitzer the
displacement of the panoramic telescope is 15.23 inches to the
left of and 10.61 inches above the axis of the bore, and the dis-
placement of the elbow telescope is 13.375 inches to the right
of and 8.375 inches above the axis of the bore. Aiming posts
with wooden blocks or markers attached make a suitable test
target. Tests can be made without the bore sights by sight-
ing through the firing lock recess in the breechblock or
through a brass cartridge case with the primer removed,
using improvised cross hairs at the muzzle.
c. Gunner' si quadrant — (1) End -for- end test . — (a) Set
both the graduated arc and index arm (sliding level) scales
at zero, and tighten the clamp screw.
(b) Place the quadrant on the leveling plates of the howitzer
and center the bubble, using either elevating handwheel of
the piece.
(c) Reverse the quadrant on the leveling plates. The
bubble should recenter itself. If it does not, change the set-
ings until the bubble is centered and take the reading. In
the case of a minus correction it will be necessary to set the
graduated arc scale one notch below zero, and move the slid-
ing level initially to the opposite end of the index arm. The
correction (the setting to be used in getting a true horizontal)
is one-half of the displacement measured, in the same sign.
54
105-MM HOWITZER M2
53
If the necessary correction exceeds 0.3 mil, the quadrant
should be adjusted by ordnance personnel at the earliest
opportunity.
(2) Index arm test . — Set a reading of any multiple of 10
on the quadrant and place the sliding level at zero. Level the
bubble by means of either elevating handwheel of the piece.
Move the index arm one notch down, and slide the level vial
to the opposite end of the scale. The bubble should remain
centered.
(3) Comparison test . — Successively place the five quadrants
of the battery on the leveling plates of a piece which is laid
at any selected elevation. Repeat the same process for several
other elevations and list the reading of each quadrant at each
elevation. Determine a mean correction for each quadrant
and apply this as a correction constant. If any quadrant
exceeds an error of 0.3 mil it should be adjusted by ordnance
personnel at the earliest opportunity.
d. Rapid daily test . — The on-carriage fire-control equip-
ment is rapidly checked for correct adjustment in the fol-
lowing manner:
(1) The chief of section sets the gunner's quadrant at zero,
places it on the leveling plates, and No. 1 levels the piece.
(2) No. 1 sets the angle- of- site scales at 300 and centers
the cross-level and angle-of-site bubbles. The elevation
scales should read zero. (The range drum will not read
exactly zero due to the allowance for jump.)
(3) The gunner centers the longitudinal and cross-level
bubbles of the telescope mount. The elevation indexes should
be in coincidence.
(4) Nos. 1 and 2 install the bore sights and, if necessary,
set up the testing target. The gunner lays the piece by bore
sighting on the testing target or distant terrain object.
(5) The gunner lays the center vertical cross hair and the
zero horizontal cross hair of the telescope reticule on the
proper portion of the test target. If the telescope is in ad-
justment the azimuth and elevation scales and their respec-
tive micrometer scales will indicate zero deflection and eleva-
tion.
(6) No. 1, by observation, restores the range lines in the
reticule of the elbow telescope to the horizontal with the erect-
ing knob. The N (normal) cross hair of the reticule should
be on the appropriate line of the test target.
55
53
FIELD ARTILLERY
(7) If the foregoing tests indicate that some portion of
the mechanism is out of adjustment, it should be adjusted
by following the procedure outlined in c above and / and g
below, or a correction should be determined, written on some
convenient location such as the shield, and used until there
is an opportunity to adjust the faulty mechanism.
e . Verification and adjustment of the telescope mount and
the panoramic telescope. — Periodically, and whenever the
mechanism is found to be out of adjustment, a detailed test
and adjustment should be made. For this purpose it is de-
sirable to have the howitzer on an approximately level plat-
form or the howitzer trunnions level. It is assumed that all
lost motion has been eliminated and that cross-level bubbles
are in adjustment. (For details see TM 9-325.) Tests and
adjustments are performed in sequence as follows:
(1) Elevation indexes of telescope mount. — Lay the how-
itzer at zero elevation with the gunner’s quadrant and center
the cross-level and longitudinal -level bubbles. The elevation
indexes should coincide; if they do not, loosen the two screws
in the adjustable index and slide it into coincidence with the
fixed index. Tighten the screws and recheck.
(2) Deflection and range scales of the panoramic tele-
scope. — Bore sight on the test target or a distant terrain
object. Insure that the elevation indexes of the telescope
mount are in coincidence. Using the appropriate knobs of
the telescope, place the center vertical cross hair and zero
horizontal cross hair of the telescope reticule on the proper
portion of the test target. If the azimuth and elevation
scales and their respective micrometer scales do not indicate
zero deflection and elevation, adjust in the following manner:
(a) Deflection adjustment. — Turn the azimuth worm knob
of the telescope until the center vertical cross hair is on the
appropriate line of the test target. Loosen the screw in the
center of the azimuth micrometer index and, while holding
the azimuth worm knob, slip the index until it corresponds
with the deflection index. Tighten the screw and recheck.
This adjustment must not be made by moving the headless
adjusting screws in the telescope socket. If necessary, the
main azimuth scale should also be adjusted to zero.
(b) Elevation adjustment. — Turn the elevating knob of
the telescope until the zero horizontal cross hair of the reti-
cule corresponds with the appropriate mark of the testing
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105 -MM HOWITZER M2
53
target. Loosen the screws in the end of the knob and, holding
the knob, slip the elevation micrometer until the zero gradua-
tion lines up with its index; then tighten the screws and
recheck the setting.
/. Verification and adjustment of range quadrant. — (1)
Move the range drum assembly indexes into coincidence. The
elevation micrometer scale and the elevation scale should
read zero. The range drum will indicate a reading slightly
greater than zero if properly assembled.
(2) With the range drum properly assembled, if the eleva-
tion micrometer scale does not read zero, it is adjusted in the
following manner:
(a) Loosen the three screws in the micrometer knob.
(b) Without moving the knob, slide the zero of the mi-
crometer scale into coincidence with the index.
(c) Tighten and recheck.
(3) With the elevation micrometer scale in adjustment, if
the elevation scale does not indicate zero, it is adjusted in
the following manner:
(a) Loosen the two screws in the index. Move the index
opposite the zero graduation.
(b) Move the index into coincidence with the zero gradua-
tion.
(c) Tighten the screws and recheck.
(4) With the elevation micrometer scale and the elevation
scale in adjustment and set at zero, the trunnions and the
axis of the bore are accurately leveled, the angle of site is
set at 300, and the cross-level bubble is centered. If the
longitudinal-level bubble is not centered, the range quadrant
is adjusted in the following manner:
(a) Center the longitudinal bubble by means of the angle-
of-site knob,
(b) While holding the angle-of-site knob, loosen the clamp-
ing screw in the meter of the knob and slip the angle-of-
site micrometer to indicate zero. Tighten the clamping screw.
(c) If necessary, loosen the two screws which secure the
angle-of-site scale and shift the scale so that the “3” gradua-
tion registers at the index line. Tighten the screws to secure
the scale in this position.
id) Recheck. Further adjustment, if required, is to be
performed only by authorized ordnance personnel.
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53
FIELD ARTILLERY
g. Verification and adjustment of the elbow telescope and
its mount . — With the axis of the trunnions leveled, bore sight
on the test target. By observation, correct the reticule to
the horizontal by means of the erecting knob. If the N cross
hair is not on its line of the test target, put it on in the fol-
lowing manner:
(1) Loosen the worm clamping bolt.
(2) With a screw driver, move the elevating adjusting
worm to bring the N cross hair in coincidence with the proper
line of the target.
(3) Tighten the worm clamping bolt.
(4) Recheck.
o
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