Document text
BASIC FIELD MANUAL
BROWNING MACHINE GUN,
CALIBER .30, HB, M1919A4
GROUND
UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON: 1940
For sale by the Superintendent of Documents, Washington, D.C. - Price 30 cents
TABLE OF CONTENTS
Mechanical Training.
Section
I. Description 1
II. Disassembling, assembling and changing parts 4
III. Care and cleaning 11
IV. Mechanical functioning 14
V. Stoppages and immediate action 18
VI. Tripod mounting 21
VII. Accessories 23
VIII. Fire control instruments 27
IX. Individual safety precautions 29
X. Ammunition 30
FM 23-45 Basic Field Manual
BASIC FIELD MANUAL
BROWING MACHINE GUN, CALIBER .30, HB M1919A4
GROUND
(The matter contained herein supersedes chapter 1, part seven, Basic Field Manual,
July 1, 1937.)
MECHANICAL TRAINING
Paragraphs
Section I.
Description
1-8
II.
Disassembling, assembling and changing parts
9-21
III.
Care and cleaning
22-26
IV.
Mechanical functioning
27-39
V.
Stoppages and immediate action
40-42
VI.
Tripod mounting
43-44
VII.
Accessories
45-52
VIII.
Fire control instruments
53-54
IX.
Individual safety precautions
55-58
X.
Ammunition
59-66
Section I
DESCRIPTION
■ 1. PRINCIPLE OF OPERATION. — The machine gun, caliber .30, M1919A4, is recoil
operated, belt fed, and air cooled. In recoil operation the rearward force of the
expanding powder gas (kick) furnishes the operating energy. The moving parts, while
locked together at the moment of the explosion, are left free within the receiver to be
forced to the rear by the recoil. This movement is controlled by means of various
springs, cams, and levers, and is utilized to perform the necessary mechanical
operations of unlocking the breech, extraction and ejection of the empty case, and
feeding in of the new round, as well as cocking, locking, and firing the mechanism. (See
fig. 1.) The receiver mechanism is for all practical purposes the receiver of the
Browning machine gun, M1917.
■2. COOLING SYSTEM. — The machine gun, caliber .30 M1919A4, is provided with a
heavy barrel which is exposed to the air. This factor serves to keep the gun at operating
temperatures under normal conditions, i.e., at the rate of about 60 rounds per minute
for about 30 minutes.
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FM 23-45 Basic Field Manual
BELT FEED SLIDE
BARREL JACKET FRONT SIGHT
BARREL
COVER REAR SIGHT
j BACK PLATE
GRIP
TRIGGER
FIGURE 1. — Browning machine gun, M1919A4
■3. FEED BELT. — Woven fabric belts of a capacity of 150 rounds, equipped with
brass strips at each end to facilitate loading, are normally used with the ground light
machine gun.
■4. MOUNTINGS.
a. The ground light machine gun normally is mounted on the light machine gun
tripod M2, a description of which is given in section VI.
b. In motorized or mechanized units, the light machine gun is mounted on vehicular
mounts of several types, but a light machine gun tripod M2 is usually carried for each
gun to be used when the gun is fired from the ground.
■5. GENERAL DATA. — General data for the light machine gun and mount are as
follows:
■6. SIGHTS.
a. Front. — The front sight consists of a front sight blade, a front side body, a front
sight post, and a plunger mechanism. The front sight post pivots on the front sight
bearing screw when folded for convenience in packing. The plunger mechanism
provides a locking device to keep the front sight post in its upright position when the
gun is being fired. The front sight is attached to the front end of the receiver by means
of a screw. The height of the front sight is such that when the rear sight slide is set at
an elevation a bullet fired from the gun will strike a target at a distance corresponding
to the elevation set on the rear sight.
b. Rear. —
(1) The rear sight (fig. 2) is of conventional type. It consists of a rear sight leaf,
carrying a peep in the slide mounting, pivoted on the rear sight base, and adjustable
for windage. The rear sight base mounts the rear sight leaf and rear sight leaf spring.
It is secured to the left side plate of the receiver by three screws in the flange of the
base.
(2) The rear sight leaf is graduated for elevation in lOOyard divisions up to 2,400
yards. The peep of the rear sight slide is 0.081 inch in diameter. Motion of the rear
sight slide is accomplished by rotation of the elevating screw knob.
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FM 23-45 Basic Field Manual
FIGURE 2.— Rear sight.
This elevating screw mechanism is equipped with a mil click device which may be used
in conjunction with a mil scale engraved on the left side of the rear sight leaf to
measure or establish angles of elevation in mils.
(3) The windage screw mechanism also incorporates a mil click device. Adjustment
of the rear sight leaf in windage is accomplished by rotation of the windage screw knob.
Amount of motion permitted is 10 mils right or left from zero.
(4) The sight radius is 13.94 inches.
■ 7. PINTLE. — The pintle of the light machine gun (ground), although technically not
a part of the gun, is permanently assembled thereto by a bolt through the trunnions of
the pintle and the trunnion hole of the receiver of the gun. Failure to keep this bolt
tight will result in inaccuracy of fire. This pintle is tapered and mates with the
corresponding tapered pintle bushing of the tripod mount M2 head. This tapered pintle
thus serves as a tight wearing union between the receiver of the gun and its mounting.
The pintle is secured in its mounting by the engagement of a spring actuated pintle
latch of the mounting in a corresponding annular groove of the pintle.
■8. ELEVATING AND TRAVERSING MECHANISM.
a. As with the pintle, the elevating and traversing mechanism is not technically a
part of the gun. However, the elevating and traversing mechanism is permanently
secured to the receiver of the gun by a bolt through the head of this mechanism and the
elevating bracket of the gun. In guns of new manufacture, the elevating bracket is
integral with the bottom plate.
b. The elevating and traversing mechanism, when used with the tripod M2, consists
of an upper elevating screw; a lower elevating screw; an elevating handwheel assembly
secured to the head of the lower elevating screw; a housing mating with the lower
elevating screw; a traversing block mounted by a swivel joint to the lower elevating
screw housing.
(l) The upper elevating screw terminates at its upper end in an offset head which
incorporates a recess for the bolt which assembles the entire elevating and traversing
mechanism to the gun. The mechanism is properly assembled to the gun when the
offset head points to the rear, thus permitting the mechanism to be folded to the rear
and seated in its recess in the duralumin grip. The inner elevating screw is externally
threaded to mate with the internal threads of the lower elevating screw. It is equipped
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FM 23-45 Basic Field Manual
with a longitudinal slot in which is seated an engraved scale. This scale is utilized to
indicate plus or minus increments of elevation given the mounted gun. It is subdivided
into 50-mil graduations and is read by noting the position of the upper edge of the
traversing bar and the traversing slide lock lever preferably engaged. (When firing on
rapidly moving ground targets, the traversing clamp is not engaged, although the
traversing block must be retained in firm contact with the traversing bar.)
(2) Movement of the light machine gun in traverse, when mounted on the tripod
M2, is accomplished by moving the gun right or left as desired, the traversing clamp
being disengaged from the traversing bar but the traversing block remaining in firm
contact with the traversing bar.
Section II
DISASSEMBLING, ASSEMBLING, AND CHANGING PARTS
■9. GENERAL.
a. Disassembling may be considered under two general heads: first, removal of
groups to the extent required for ordinary cleaning and minor repairs; and, second,
detailed disassembling, involving removal of all components from each group.
b. A group is a number of parts, contained in a common housing, which function as a
unit.
c. The removal of the different groups from the gun and complete disassembling of
the groups to be disassembled by the using services can be accomplished with the tools
provided.
■ 10. REMOVAL OF GROUPS FROM GUN.
a. Backplate.
(1) Pull back on latch and raise cover. With the left hand pull back bolt handle and
hold it in the rearmost position.
(2) Insert rim of a cartridge in slit in end of driving spring rod. With slit
horizontal, push in driving spring rod as far as it will go and turn it clockwise one-
quarter turn until slit is vertical. In this position the lugs on it will engage in their
recesses in the bolt.
(3) Push bolt handle forward about an inch to free the rear end of driving spring
rod from backplate.
(4) Push latch forward and lift out backplate.
b. Bolt handle. — Pull bolt all the way back and remove bolt handle.
c. Bolt. — Remove bolt from rear end of receiver being careful not to handle driving
spring rod.
d. Lock frame. — Insert nose of cartridge through hole in the right side of receiver and
push in on trigger pin. Grasp trigger and pull lock frame, barrel extension, and barrel
out of receiver. Hold barrel in one hand, lock frame in the other, and push forward on
accelerator. This separates lock frame and barrel extension.
e. Barrel extension and barrel. — Unscrew barrel extension from barrel.
f. Latch. — With the left hand, palm up, against the rear of the receiver to prevent
dropping the latch spring, pull latch to rear until it separates from the plate. Guns of
recent manufacture have the latch spring riveted to the latch
g. Latch spring. — If not riveted lift the latch spring from its pin in the latch.
h. Cover.
(l) Guns of early manufacture.
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FM 23-45 Basic Field Manual
(a) Turn cover pin spring up and remove pin,
(b) Remove cover.
(2) Guns of new manufacture.
(a) Remove cotter pin from cover bolt.
(b) Place screwdriver blade of combination tool in slot in cover bolt to prevent it
from turning and with a wrench remove the nut.
(c) Remove cover bolt, cover catch spring, and fixed and movable plates.
id) Remove cover.
NOTE. — To prevent undue wear, the cover and latch should not be removed except when necessary for cleaning or
replacement of parts.
■ 11. REPLACING GROUPS In GUN. — In general, the groups are replaced in the gun in
reverse order.
a. (l) Guns of early manufacture. — Replace cover. Insert cover pin and lock it by
turning cover pin spring forward into its seat in trunnion block. Some models have a
cover pin which is locked by inserting and spreading a cotter pin through a hole in the
cover pin.
(2) Guns of new manufacture. — Replace cover. Place cover latch spring on bolt and
position the fixed and movable plates. Insert cover bolt into cover hole. Place
screwdriver blade of combination tool in slot in cover bolt to prevent it from turning,
and assemble nut to cover bolt using a wrench until the desired tension is obtained.
Replace cotter pin.
b. Seat rounded end of latch spring in latch seat, placing hole in spring over pin, bent
side of spring away from latch. Holding spring in place with the fingers, push latch
onto top plate from the rear, free end of the spring to the front, then force the latch
home. If the spring is allowed to slip from its seat, the latch will not function, and the
spring will jam the latch so that it cannot be removed without breaking.
c. Screw barrel into barrel extension until barrel locking spring begins to engage in
barrel notches.
d. Insert barrel and barrel extension into receiver until the forward end of barrel
extension is opposite the rear end of receiver.
e. Holding barrel extension with one hand, take lock frame in other hand, with index
finger beneath and supporting accelerator. Place claws of accelerator in front of and
against T-lug. Insert front projections of lock frame into slots of barrel extension and
push forward until accelerator turns backward, locking lock frame to barrel extension.
Push down tips of accelerator to insure positive locking.
f. Push parts into gun, forcing trigger pin inward to clear it from right side plate, and
push forward until a click is heard as trigger pin springs out into its seat in the right
side plate. (If barrel hangs on front barrel bearing, reach forward under jacket and
align it.)
g. Push cocking lever forward and insert bolt, pushing down on rear end of trigger to
prevent ejector from tripping accelerator.
h. Insert bolt handle through large opening at rear of slot and push it forward about
1 inch, being sure that collar on handle is inside right side plate.
i. Push forward on latch and replace backplate.
j. Hold bolt handle fully back with left hand. Place rim of cartridge in slit in end of
driving spring rod, and turn rod one-quarter turn counterclockwise until slit is
horizontal. This releases driving spring. Allow bolt to go forward.
k. Make head space adjustment as follows:
(l) Pull bolt to rear about % inch.
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FM 23-45 Basic Field Manual
(2) Screw barrel into barrel extension (by using point of a cartridge or the
combination tool in barrel notches) until the action will just close (recoiling parts will
go fully forward) without being forced.
(3) Then unscrew barrel two notches.
CAUTION' Care must be exercised to avoid roughening the barrel surface during the
adjustment. Also, the packing must not bind the barrel, as a false adjustment will
result in such a case.
7. Position belt feed lever stud over Cam groove in bolt and close cover.
m. Pull trigger.
NOTES. —
1. Head Space.
a. The head space of a military weapon with a cartridge fully seated in the chamber is the distance between
the base of the cartridge and the face of the bolt.
b. In Browning machine guns, the head space is adjusted by obtaining the proper distance between the
forward part of the bolt and the rear end of the barrel. The head space adjustment must be checked before firing.
2. Effect Of Head Space. Adjustment.
a. General. — Probably the most important adjustment of the machine gun is the head space adjustment.
Tests show that shot patterns are not adversely affected by the head space when the guns are adjusted as outlined
above. In fact, better uniformity of shot patterns will be obtained when the guns are operated with the above
adjustment which is based on the fundamental design of the weapon. Tests have also proved that guns may be
damaged and in some cases put out of action by using unapproved methods of adjusting the head space. Many
reports show that difficulties with improperly guided belts and with firing mechanisms have been attributed to
undue concern over head space adjustment.
b. Insufficient head space. — When the head space adjustment is too tight, poor functioning will result, as the
breech lock will' not fully enter its recess in the bolt. This condition may damage the barrel extension, bolt, or breech
lock. Extraction trouble may also occur due to improper timing Or locking and unlocking. Further- with a tight head
space adjustment the gun operates sluggishly because of the binding of the moving parts.
c. Excessive head space. — If the head space is too great, a separation Of the cartridge case may occur. Should
there be any weakness in the head of the cartridge case, such as a split case, the possibility of a rupture is increased
by excessive head space.
3. QUICK HEAD SPACE ADJUSTMENT. — After the head space adjustment has been determined by the method
described in paragraph Ilk, the notch in which the barrel locking spring is engaged may be marked with a center
punch. Then to make the correct head space adjustment, during the assembly of the gun, screw the barrel all Of the
way into the barrel extension and then unscrew the barrel until the barrel cocking spring is in the marked notch.
■12. Detailed Disassembling Of Bolt.
a. Turn the extractor up and remove it to the left (fig. 5).
b. Great care should be exercised in removing the driving spring rod from the bolt as
the force of the driving spring when released can easily cause the rod to slip away
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FM 23-45 Basic Field Manual
FIGURE 3. — Tight head space adjustment.
FIGURE 4. — Loose head space adjustment.
from the hand and possibly result in serious injury. To remove driving spring rod, place
protruding end of rod on the table or a, block of wood. With bolt firmly grasped by the
right hand (palm of the hand over face of bolt), press down and at the same time turn
bolt one-fourth turn to the left until lugs on rod leave their recess in bolt. Slowly
release pressure on bolt, allowing it to rise under the action of driving spring until
about 3 inches of rod protrude. With the left hand grasp protruding portion of rod and
spring; raise both hands and the bolt from the table, keeping rod and spring in their
same position relative to bolt. Separate rod and spring from bolt with a quick jerk. The
quick, separating jerk will not allow spring to kink. Separate driving spring rod and
driving spring.
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FM 23-45 Basic Field Manual
SEAR SPRING PIN
COLT
FIRING PIN EXTRACTOR
SEAR SPRING
FIRING PIN SPRING ^
DRIVING SPRING < 17 1- COCKING LEVER PIN
§ SEAR
COCKING LEVER ^ DRIVING SPRING ROD
Figure 5. — Bolt group.
c. Turn the top of cocking lever to the rear of bolt and withdraw cocking lever pin to
the left of bolt.
d. Lift out cocking lever.
e. Release firing pin by pushing down on sear. Hold bolt in the left hand, the front
end toward the body, top up, with the index finger of the left hand beneath and
supporting the sear. Use the nose of a cartridge, placed near the end of sear spring, to
push downward and to the right on spring to seat it in cut in bolt. This releases sear
which is removed at the bottom of bolt.
f. Turn sear spring back to the left to clear the cut. Push nose of a cartridge into the
hole in the bottom of bolt to start sear spring pin moving. To complete the removing of
sear spring, place the top end of cocking lever well under sear spring and pry down
against the edge of bolt.
g. Place the palm of the right hand over the rear of bolt, tilt the rear end of bolt
down, and firing pin will drop out.
■ 13. Assembling Of Bolt.
a. Place firing pin in bolt, striker downward and to the front, and tilt the front of bolt
downward until striker projects through the small hole in the front of bolt.
b. Replace sear spring by pushing with a cartridge on top of pin, avoiding pressure
on spring proper.
c. Hold bolt in the left hand, front end toward the body, top up. With point of a
cartridge placed near the end of sear spring, push downward and to the right to seat it
in cut in bolt.
d. Push sear upward from the bottom, notched projection toward the front of bolt,
and hold with first finger of the left hand while pressing downward and to the left on
sear spring with a cartridge to engage the end of sear spring in sear.
e. Replace cocking lever, making certain that the rounded nose on the lower end is to
the rear of bolt so that it will properly engage in the recess in firing pin.
f. Insert cocking lever pin from the left side of bolt. The upper end of cocking lever
should be to the rear of bolt before inserting pin, as this aligns cocking lever for the
return of pin.
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FM 23-45 Basic Field Manual
g. Cock by pressing forward on cocking lever. Turn cocking lever to the rear and
press down on sear with a cartridge to release firing pin and test the correctness of the
assembly. Recock the assembly.
h. The same care' should be exercised in assembling the driving spring rod to the bolt
that is exercised in removing it. Place driving spring on driving spring rod. With the
back end of the rod resting on a table or a block of wood, gather as much of the spring
on the rod as can he held compressed by the thumb and fingers of the left hand. With
bolt securely held in the right hand, the front end of bolt in the palm of the hand, slip
bolt over the end of spring. Push downward to compress spring and allow lugs on rod to
enter slot in bolt. Turn bolt slowly 90° clockwise until slit in rod is crosswise to slot in
bolt.
i. Insert pin on extractor into the rear one of the two large holes in the left side of
bolt, extractor pointing up. Turn extractor downward toward the front to engage collar
on extractor under collar cut in bolt.
■ 14. Detailed Disassembling Of Lock Frame (fig. 6).
a. Grasp head of trigger pin between the thumb and first finger of the right hand and
remove it to the right. Lift out trigger. If pin is too tight to permit its removal in this
manner, it must be drifted out. DO not remove trigger pin spring except when
necessary.
LOCK FRAME
TRIGGER PIN
BARREL PLUNGER
Figure 6. - Lock frame group.
b. Push out accelerator pin and remove accelerator.
c. Hold lock frame with the left hand, projections pointing upward, slot to the left,
separator between the second and third fingers, first and second fingers gripping barrel
plunger spring. With the thumb of the right hand, press down and out on barrel
plunger to disengage plunger guide pin from slot. Allow spring, with plunger, to rise
slowly Lift out spring and remove it from barrel plunger.
■ 15. Assembling Lock Frame.
a. Assemble barrel plunger spring to barrel plunger, being careful that the more
tightly fitting end of barrel plunger spring is pushed up against the head of barrel
plunger. Hold lock frame with the left hand, projections pointing upward, slot to the
left, lock frame separator between the second and third fingers. Seat the end of barrel
plunger spring in the recess in lock frame separator, barrel plunger guide pin facing
the slot in lock frame. Using the first and second fingers of the left hand to prevent
spring from buckling, press down with the thumb of the right hand on the end of barrel
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FM 23-45 Basic Field Manual
plunger until barrel plunger guide pin can be seated in the slot. Care should be taken
that the action of the spring does not cause the plunger to slip out of the hand.
b. Replace accelerator with the tips up and the rounded surface to the front. Insert
accelerator pin, taking care that both ends of pin are flush with the sides of lock frame.
c. Push the front end of trigger up between separator and spacer, placing the center
in its square seating. If trigger pin spring has been removed, seat spring on trigger pin,
placing the small end of spring toward the head of pin. Replace pin from the right.
■ 16. Detailed Disassembling Of Barrel Extension (fig. 7).
a. Insert the rim of a cartridge under the front edge of barrel locking spring and pull
it out to the front.
b. Push out breech lock pin and remove breech lock.
■ 17. Assembling Barrel Extension.
a. Place breech lock in its slot, taking care that the double beveled surface is up and
to the front. Insert breech lock pin and insure that both ends of pin are flush with the
sides of barrel extension.
b. Insert barrel locking spring in the seating in the left side of barrel extension, hook
inward, and force home as far as it will go.
■18. Detailed Disassembling Of Cover (fig. 8).
a. Remove cotter pin or cap from belt feed lever pin. Remove belt feed lever pin.
b. Withdraw belt feed lever from belt feed slide and remove slide.
c. Insert the nose of a cartridge between cover extractor spring and the notch in
cover extractor cam. With the thumb of the left hand over spring, pry out on spring to
disengage from cut. Lift out spring from its seat against stud.
BARREL LOCKING SPRING
BREECH LOCK PIN
a
BARREL
FIGURE 7. — Barrel and barrel extension group.
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FM 23-45 Basic Field Manual
FIGURE 8. — Feed group.
■ 19. Assembling Cover.
a. Place the forked end of cover extractor spring under stud on cover. Press
downward with the thumb on the other end of spring, at the same time pushing toward
stud, and seat projection of spring in the notch of cover extractor cam.
b. Replace belt feed slide in its grooves in cover, taking care that pawl is pointing to
the right as cover goes on the gun.
c. Place front end of belt feed lever in the cut, stud on lever away from cover and to
the rear. Insert belt feed lever pivot pin. Replace cotter pin or cap.
■20. Disassembling Of Parts Dismounted Only For Repair.
a. Shock absorbing group. - Unscrew adjusting screw and remove adjusting screw
plunger and spring. Remove buffer disks (in later guns these are replaced by heavy
recoil spring), buffer plug, buffer ring, and buffer plate through the rear end of the grip.
Replace in the reverse order.
b. Belt holding pawl.
(1) Hold down belt holding pawl and withdraw belt holding pawl split pin to the
rear.
(2) Lift off belt holding pawl.
(3) Lift belt holding pawl spring from its seating.
(4) Replace in the reverse order.
■21. CHANGING PARTS. — If the time element is important, a broken minor part should
be replaced by substituting a complete spare part which contains it. Thus a broken
firing pin would be remedied by changing bolts. Replacement parts in the spare parts
box should be repaired as soon as opportunity permits. In event the bolt, barrel, or
barrel extension is changed, adjust the head space.
Section III
CARE AND CLEANING
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FM 23-45 Basic Field Manual
■22. GENERAL. — It is essential that the gun be maintained in the best mechanical
condition at all times. It must always be kept clean and covered with a light coating of
oil. Particular attention must be paid to the bore. Care and cleaning will not be
confined to the gun alone but will include the tripod and all accessories. Belts and
ammunition must be kept clean and dry.
■23. Gun, Tripod, And Spare Parts.
a. Bore. — When firing is completed the bore should be cleaned immediately as
follows:
(1) Disassemble groups from gun.
(2) Place barrel with barrel extension attached, muzzle down, in a vessel
containing hot water and soap or hot water alone.
(3) Use cleaning rod with flannel patch to pump water hack and forth through
the bore for about 1 minute. (A soft wire brush may be used to remove
particles which are stuck to the bore.)
(4) Dry and clean bore thoroughly then apply a light coat of lubricating oil.
(5) Inspect daily and repeat the above treatment until the bore shows no signs of
corrosion.
b. Moving parts. — The moving parts should be kept clean and lubricated before,
during, and after firing. In lubricating the parts during firing, care should be exercised
to apply oil frequently but sparingly to those parts where actual friction exists. These
include the cam groove and the cocking lever. Excess oil generates smoke which
interferes with observation.
c. Front barrel bearing. — Carbon is deposited in the front barrel bearing during
firing of the gun. If this deposit is not removed periodically, it will eventually cause the
barrel to bind. To remove —
(1) Using a combination tool, unscrew front plug.
(2) Soften carbon with oil and scrape it out.
(3) Replace plug.
NOTE. — Before guns are stored, the front barrel bearing should be removed and the carbon deposits thoroughly
removed from the bearing and barrel jacket.
d. Tripod.
(1) Keep all moving parts lightly oiled. Avoid leaving excessive oil in interior of
tripod head as dirt and sand will collect and interfere with positive locking of legs. The
pintle bushing should be cleaned and lightly oiled. Oil should not be placed in the
seating of the traversing dial, as it will cause dirt to collect and interfere with easy dial
adjustment.
(2) All steel parts of the M2 tripod are given special treatment to prevent
rusting. This protection may eventually wear through where sliding parts are in
contact and rust will then occur. In the removal of such rust only the finest crocus cloth
should be used and this sparingly.
(3) AU parts of the M2 tripod are carried in local stock by the Ordnance
Department. In case of dents or bending of parts that interfere with smooth operation
in mounting and dismounting the tripod, temporary repair by either filing down dents
or straightening the bent part may be necessary. However, the damaged part should be
replaced at the earliest opportunity by Ordnance Department personnel.
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FM 23-45 Basic Field Manual
e. Spare parts. — Spare parts must be kept free of dirt and moisture and be lightly
coated with oil. When first received, all traces of rust-resisting compound should be
removed.
■24. Care During Cold Weather.
a. Use aircraft instrument and machine gun lubricating oil (U. S. A. Spec. 2-27D) for
a lubricant.
b. Test the gun frequently to see that it functions properly.
■25. Care During Gas Attack.
a Cover ammunition, if practicable.
b. Oil gun and mount to prevent corrosion (effective for about 12 hours). Cosmoline
resists gas corrosion more than lighter oil.
c. Cover gun with a waterproof cover, if practicable.
d. As soon as possible after a gas attack, wash all of the parts of the gun in the
neutralizing solution issued for the purpose, or in its absence boiling water containing
soda. Dry them and then cover them with a light coat of oil.
e. Remove all traces of gas from the ammunition with the neutralizing solution
issued for the purpose, then dry thoroughly.
■26. Point To Be Observed Before, During And After Firing. — The following list
of points to be observed before, during, and after firing will be found useful as a guide
for the proper care of the gun. It will also serve as a guide for inspection.
Before
During
During
temporary
cessation
After
Bore
Look through and
Clean bore
Clean and
clean
lightly oil bore
with a patch.
Moving Parts
Oil and test for
Keep oiled
Inspect and
Remove bolt,
worn or broken
oil; clean dirt
lock frame,
parts. See that
from belt
barrel
parts function
holding pawl.
extension, and
without excessive
barrel. Clean,
friction
oil, and release
firing pin.
Head Space
Make correct
Tighten if
Test
Adjust
adjustment and
several
correctly and
test (note, par.
separated
test. Examine
ll). Examine
cases occur.
barrel locking
barrel locking
spring.
spring
Rear sight
Clean and free
Keep properly
Keep
Clean and oil.
and wind
from grease. See
set
properly set
Set sight at 500
gage
that sight is in
and wind gage
good mechanical
at zero.
condition. Set
sight at 500 and
wind gage at zero
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FM 23-45 Basic Field Manual
Tripod
Set tripod firmly
with no lost
motion. Verify
that traversing
bar sleeve latch
is properly
seated.
Keep firmly
set.
Examine
Clean and oil.
~D ,-.1 4-„ J
celts and
becure sumcient
Keep belt m
Clean, repair,
ammunition
supply of
line with feed
and refill all
ammunition.
opening.
belts. Separate
Inspect
Watch
live rounds
ammunition.
ammunition
from empty
Keep belts dry
supply
cases. Inspect
ammunition.
Ull
See that oilcan is
full
Keiill oilcan.
Kei il 1 oilcan.
Spare parts
Keep clean and
Keep within
Make
Check, replace
and tools
oiled. See that
reach
repairs.
broken or
kits are complete
Replace
broken or
worn parts.
missing parts,
clean, and oil.
Section IV
MECHANICAL FUNCTIONING
■27. GENERAL. — The soldier should have a practical working knowledge of the
mechanical operation of the machine gun so that he will be able to keep it in action
during combat. Although many parts of the gun operate simultaneously, the subject of
functioning is divided into phases to facilitate instruction. The explanation of
mechanical functioning begins with the gun assumed to be loaded and ready to fire.
a. To half load. — With cover open or closed, enter belt through feedway from left to
right. Pull belt through feedway until the first round is in place on the right of
beltholding pawl. Close cover if open. Pull bolt fully to the rear and release it.
b. To load. — Load is executed the same as half load except that bolt is pulled to the
rear and released twice.
c. To unload. — Raise cover, remove belt, pull bolt to the rear and hold it, look or feel
to see that there is no ammunition in the gun, lower extractor, release bolt, lower
cover, and then pull trigger.
d. To clear gun. — Raise cover, remove belt, pull bolt to the rear and hang it in its
rearmost position by engaging extractor cam plunger in rear of extractor feed cam, and
inspect the gun to see that there is no ammunition in it. As an additional precaution, a
wooden clearing block will be inserted between the face of the bolt and the rear end of
the barrel.
■28. TRIGGER ACTION. — As the trigger is pivoted, its rear end is raised if its forward
end is lowered. The trigger cams on the front end of trigger, through their engagement
with cams on sear, force sear down against the action of sear spring until the shoulder
of firing pin is released by sear notch. The firing pin spring then forces firing pin
forward to strike primer.
■29. Backward Movement of Recoiling Parts (figs. 9 and 10). — The explosion
forces the recoiling parts (barrel, barrel extension, and bolt) backward about 5/8 inch.
During the first half of this movement the parts are locked together.
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FM 23-45 Basic Field Manual
When the breech lock clears the breech lock cam, it is forced down by the front
projections of the lock frame acting on the breech lock pin. This unlocks the bolt from
the barrel extension, permitting the bolt to continue to the rear. AS the barrel
extension comes to the rear, the barrel plunger spring is compressed, and the rear of
the barrel extension strikes the accelerator and turns it backward.
EXTRACTOR ,„ . „,„„ BACK PLATE
BARREL / firing PIN
BARREL EXTENSION / 7
FIRING PIN SPRING ] ACCELERATOR
BREECH LOCK CAM
TRIGGER
LOCK FRAME
FIGURE 9. — Relation of parts in forward position.
■30. Backward Action Of Accelerator (figs. 9 and 10).— AS the accelerator turns
backward its tips strike the bottom projections on the bolt and accelerate it to the rear.
BREECH LOCK PIN
FIGURE 10. — Barrel, bolt, lock frame, and barrel extension in firing position.
The claws of the accelerator engage the shoulder of the T-lug and lock the barrel
extension to the lock frame. The barrel plunger spring is thus held compressed. The
accelerator stop prevents the accelerator from turning backward too far.
■31. Backward Movement Of Bolt (figs. 9 and ll).— As the bolt moves backward the
driving spring is compressed. The bolt brings with it a cartridge from the belt, held by
the extractor, and an empty case from the chamber, held in the T-slot. The extractor
cam plunger rides along the top
FIGURE 11. — Extracting and loading mechanism.
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FM 23-45 Basic Field Manual
of the extractor cam and extractor feed cam until forced in by the beveled part of the
extractor feed cam. This permits the extractor to be forced down by the cover extractor
cam, and the plunger springs out behind the extractor feed cam.
FIGURE 12.— Belt feed mechanism.
■32. FIRST ACT Of FEEDING (fig. 12). — As the bolt moves backward, the stud on the
pivoted belt feed lever moves to the right in the cam groove, thus forcing the belt feed
slide to the left. The belt feed pawl engages on the left of the first cartridge which is
held in position by the belt holding pawl. In the event the extractor fails to, withdraw
the leading round from the belt, the finger of the belt feed pawl, riding on the top of
this unextracted round, will hold the feed pawl raised in a position where it cannot
engage on the left of the next cartridge. It thus prevents double feeding.
■33. Cocking Action (fig. 13).— AS the bolt moves backward, the upper end of the
cocking lever is forced forward in the cocking lever recess, bringing the lower end to the
rear. The lower end brings with it the firing pin, thus compressing the firing pin spring
against the sear spring pin.
FIGURE 13. Cocking mechanism.
The shoulder of the firing pin engages the notch in the sear, which is pulled upward by
the action of the sear spring, the trigger cams now being disengaged from the sear.
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FM 23-45 Basic Field Manual
■34. ACTION Of DRIVING SPRING (fig. 14).— When the rear of the bolt strikes the buffer
plate, its remaining force is absorbed in the coiled spiral spring and the buffer disks.
The force of the rearward motion of the bolt being absorbed by the buffer mechanism,
the driving spring then forces the bolt forward.
■35. FORWARD MOVEMENT Of BOLT (fig. 11).— When the bolt starts forward, the
extractor is guided downward by the action of the extractor feed cam on the extractor
cam plunger. This causes the extractor to force the cartridge down the T-slot in line
with the chamber. The ejector knocks the empty case from the T-slot and holds the
cartridge in line with the chamber. The upper end of the cocking lever is forced
backward, causing the lower end to move forward away from the rear of the firing If
the the pin is prematurely released, it is reengaged by the cocking lever and eased
forward so that the striker cannot contact the cartridge primer until after the breach
has been locked.
■36. Release Of Recoiling Parts (fig. 14) —AS the bolt goes forward its bottom
projections strike the accelerator and turn it forward. This unlocks the barrel extension
from the lock frame and releases the barrel plunger spring. When the accelerator has
TOP PLATE
FIGURE 14. — Relation of parts in backward position.
been tripped, the barrel extension and the barrel are moved forward by the forward
force of the bolt acting through the accelerator and the expansion of the barrel plunger
spring.
■37. LOADING AND LOCKING ACTION (figs. 11 and 14) .—During the latter part of
the forward movement of the bolt, the extractor rises as the plunger moves along the
top of the extractor cam. When the extractor rises, the ejector is cammed outward,
leaving the cartridge in the chamber gripped by the T-slot. The extractor grips the first
round in the belt and is held down firmly by the cover extractor spring, ready to extract
the round. The breech lock is forced upward by the breech lock cam and locks the
breech just before the recoiling parts reach the firing position. The breech lock engages
in a recess cut in the bottom of the bolt and thus locks the bolt firmly to the barrel
extension and against the rear end of the barrel.
■38. SECOND ACT OF FEEDING (fig. 12) .—AS the bolt goes forward the stud on the
pivoted belt feed lever moves to the left in the cam groove, forcing the slide to the right.
The belt feed pawl carries the first cartridge to the right against the cartridge stops,
ready to be gripped by the extractor. The next cartridge is carried over the belt holding
pawl which rises behind it and holds it in position to be engaged by the belt feed pawl
on its next movement to the left.
i39. TRIGGER ACTION IN AUTOMATIC FIRE (figs. 9, 13, and 14).— If the trigger is
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FM 23-45 Basic Field Manual
held raised, as the sear moves forward with the bolt the trigger cams engage the sear
cams and force the sear down, releasing the firing pin. The gun thus fires
automatically, repeating the operations of functioning already described. The release of
the firing pin actually takes place about 1/16 inch before the recoiling parts reach the
forward position but after the breech is locked.
■40. DEFINITIONS.—
a. A "stoppage" is any unintentional cessation of fire.
b. "Immediate action" is the procedure used for the prompt reduction of usual
stoppages.
■41. STOPPAGES. —
a. Prevention. — Stoppages will be reduced to the minimum if the gunner has a
practical working knowledge of his weapon and applies the points which should be
observed before firing Prevention is the best remedy for all stoppages.
b. Causes. —
(1) A stoppage will occur if the gun fails to feed, fails to load, or fails to fire.
(a) If the gun fails to feed, the cause for the stoppage will be found in the
ammunition belt or in the feed mechanism.
(b) If the gun feeds but falls to load, the cause will be found in the receiver. A
broken part or an obstruction on the T-slot or in the chamber is the usual cause.
(c) If the gun feeds and loads but fails to fire, the cause will be found in the
firing mechanism unless the primer of the cartridge is defective.
(2) The table following includes a comprehensive list of possible stoppages. It will
serve as a guide during instruction in stoppages or immediate action.
Section V
STOPPAGES AND IMMEDIATE ACTION
TABLE OF STOPPAGES
Stoppages
Method of preparing for instruction in
immediate action and stoppages
1.
2.
3.
4.
5.
6.
7.
8.
9.
Misfire due to defective primer.
Short round.
Bulged round.
Tight loop in belt. 1
Empty loop in belt.
Stretched or torn belt. 1
Thin rim, permitting nose of bullet to
drop below chamber. 1
Belt improperly loaded.
Battered or thick rim of cartridge.
1.
2.
3.
4.
5.
6.
7.
8. Pull cartridge partially out of belt
9. Place a battered or thick rimmed
Place a dummy cartridge in belt.
Place a short round in belt.
Insert bulged round in belt.
Do not prepare
Leave an empty loop in belt.
Do not prepare.
Do not prepare
10. Failure to remove round from
chamber
1 1 . Set back primer. 1
12. Separated case which is removed
cartridge in belt.
10. Place a dummy cartridge with rim
filed off in the chamber.
11. Do not prepare.
12. Drive the front portion of a
from chamber by new round when
cartridge securely on a dummy
cartridge. Pull bolt to the rear and
place cartridge properly on the face
bolt is pulled to the rear.
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FM 23-45 Basic Field Manual
13. Separated case, which stays in
chamber when bolt is pulled to the
rear
(Do not set up loose head space.)
14. Bullet loose in cartridge case.
Cartridge case extracted from belt
but bullet remains in belt. 1
15. Short of broken firing pin.
16. Weak or broken firing pin spring.
17. Faulty engagement of firing pin and
sear notch
18. Broken sear spring.
19. Belt feed lever pivot out, worn, or
broken
20. Bent or worn belt feed lever.
21. Belt feed pawl spring out or weak.
22. Felt feed pawl pin out or partially
out.
23. Cover extractor spring out or weak.
24. Belt feed lever bent up (stud on lever
jumps out of cam groove.
25. Damaged extractor.
26. Belt holding pawl out or spring weak.
27. Broken extractor or ejector.
28. Broken or damaged T-slot, causing
misalignment and buckling of
cartridge as bolt moves forward or
failure to extract. 1
29. Weak ejector spring causing
misalignment and buckling of
cartridge as bolt goes forward.
30. Broken barrel extension or lock
frame.
31. Defective trigger mechanism. 2
of bolt. Ease bolt forward.
13. Insert the front end of a separated
case in chamber and load
14. Do not prepare.
15. Assemble bolt with a defective
firing pin or place 5 or 6 successive
range dummy cartridges in belt for
instruction in immediate action.
16. Same as 15.
17. Assemble bolt with defective parts.
18. Same as 17.
19. Assemble cover with defective part.
20. Same as 19.
21. Remove belt feed pawl spring.
22. Remove belt feed pawl pin.
23. Remove cover extractor spring.
24. Assemble with defective part.
25. Same as 24.
26. Remove belt holding pawl.
27. Assemble bolt with defective part.
28. Do not prepare.
29. Assemble with defective part.
30. Assemble with defective part.
31. Do not prepare
1 Not prepared for instruction in immediate action.
2 Defective trigger mechanism may cause the gun to begin firing as soon as it is loaded
or continue to fire when the trigger is released. To remedy, unlatch the cover or twist
the belt, unload, disassemble the gun, and replace the defective part or parts.
c. Tools used in reduction of stoppages. — The tools commonly used in the application
of immediate action are the ruptured cartridge extractor, the combination tool, and the
cleaning rod.
(l) (a) A ruptured cartridge case in the chamber prohibits the entrance of the
succeeding round. The ruptured cartridge extractor, commonly called "clearing plug," is
used to remove the ruptured case. This tool is furnished in two types, the cartridge
form and the Mk. IV.
1. To use the cartridge form, open cover, place ruptured cartridge extractor on
feedway against cartridge stops, and engage it with extractor on bolt. Holding down on
extractor, load it slowly and smoothly into chamber, being careful to see that the
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FM 23-45 Basic Field Manual
shoulder does not strike and bur the edge of chamber. Strike forward on bolt handle to
be sure that ruptured cartridge extractor is seated in ruptured case. Pull bolt to the
rear and catch ruptured cartridge extractor in the left hand as it is ejected.
2. To use the Mk. IV, draw bolt handle to the rear and latch it. Insert nose of
ruptured cartridge extractor in chamber, handle up, push it forward to seat it firmly in
the separated case, then pull backward on handle.
(b) Separated cases should be removed from the ruptured cartridge extractor so
that it will again be ready for use. To do this, the end of the ruptured cartridge
extractor must be unscrewed, the separated case taken off, and the end screwed on
again.
(2) The use of the combination tool facilitates the removal of a round which is
stuck on the T-slot. To remove a round from the T-slot, pull bolt fully to the rear and
raise extractor. If the round does not fall out, remove it with the combination tool. If
the round is above the bolt handle slot, insert screw driver end of tool through slot and
under the rear end of cartridge and pry it up. If the round is below the slot, place screw
driver end of tool through top of receiver into cannelure of cartridge and drive it down.
(3) The cleaning rod is used to remove a case from the chamber which has not
been extracted by the bolt. To remove the case from the chamber, pull bolt fully to the
rear and hold it. Remove the following round from the T-slot. Grasp cleaning rod about
6 inches from the end, insert it into muzzle, and force case from chamber. Care should
be used not to damage the face of the bolt by striking it as the rod is shoved through
the bore.
d. Inspection of feed mechanism. — In event of recurrent or permanent failure to feed,
the feed mechanism must be inspected and the defective part replaced. This inspection
should include the following:
(1) Belt feed lever and slide. —
(a) With the bolt forward, lower cover, making sure that stud on feed lever is in
cam groove in the top of bolt.
(b) Press to the left on heft feed slide to remove the play and note whether or not
the slide protrudes to the right of the cover about 1/32 inch.
1. Kit does not, change belt feed lever and pivot.
2. If it does, and the gun has occasionally failed to feed, examine belt feed
lever for excessive wear at the pivot and stud. Also see that stud projects a sufficient
distance from cover to insure that it is positively positioned in cam groove in the top of
bolt when cover is closed. Replace defective parts.
(2) Other parts. — If the slide positions properly and no excessive play exists,
examine cover extractor spring; belt feed pawl, spring, and pin; belt holding pawl and
spring; extractor including ejector; spring and cam plunger; and T-slot, to see that
these parts are there, in good condition, and that springs are sufficiently strong to
actuate the parts properly.
■42. IMMEDIATE ACTION.—
a. General. — The procedure prescribed in immediate action for the reduction of
stoppages is based on the frequency with which the various types of stoppages occur.
Execution of this procedure by the gunner will enable him to remedy the majority of
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FM 23-45 Basic Field Manual
stoppages immediately without attempting to analyze the cause. Immediate action is
performed by the gunner. All personnel required to fire the machine gun will be
proficient in immediate action.
^.Procedure. — The procedure for immediate action is shown in the following
diagram:
IMMEDIATE ACTION
The gun fails to rife
Pull the bolt to the rear, release it, and attempt to fire
If gun still fails to fire
Tap the cover, pull the belt to the right, hold the left hand on the belt at the point
where the cartridge enters the feedway, and pull the bolt to the rear and release it.
If the belt feeds If the belt does not feed
Attempt to fire Raise the cover, remove the
first round from the belt,
If the gun still and look or feel for a
Fails to fire cartridge in the gun
Charge the bolt If the cartridge is :
In the gun Not in the gun
Remove it Reload, relay and fire
Reload, relay and fire
NOTES. — 1. If the procedure outlined above does not place the gun in action, the gunner must inspect the feed mechanism and the
working parts of the gun to include inspecting the chamber for a ruptured case in order to locate and reduce the stoppage.
2. II the bolt stops just short of home, frequently it can be pushed fully forward and firing continued without application of immediate
action. Caution: Release the trigger before pushing the bolt forward.
3. Stoppages caused by defective feed' mechanism can sometimes be remedied temporarily by pulling the belt to the right with just
sufficient force to assist the feed mechanism in positioning the leading round.
Section VI
TRIPOD MOUNTING
■43. Light Machine Gun Tripod Mount M2. —
a. This tripod (fig. 15) is a simple mount for the light machine gun and is designed to furnish the
gun with a stable mount embodying the maximum strength and rigidity consistent with desired light
weight. It is portable, easily packed, and may be used for the delivery of accurate fire on ground
targets.
b. The tripod consists of three tubular steel legs articulating in a tripod head, the two trail legs
being joined and additionally supported by a traversing bar, forming a simple Atruss, and serving as
a rear support for the mounted gun. The tripod head furnishes a front support for the mounted gun, it
being in turn supported by the short front leg.
c. Incorporated in the tripod head (fig. 1 6) is a bronze bushing, mating with the tapered steel
pintle permanently secured to the receiver of the light machine gun. The pintle is secured in its union
with the bushing by engagement of the pintle latch of the tripod in its corresponding annular groove
21
FM 23-45 Basic Field Manual
of the pintle (upper groove). The pintle latch is spring actuated and is seated in its housing on the
lower right surface of the tripod head.
d. A traversing dial graduated in major divisions of 100 mils and minor subdivisions of 25 mils,
from zero to 6,400 mils in a clockwise direction, is fitted to the tripod head by the flange of the
bronze pintle bushing. This dial is free to rotate but may be clamped in any desired position by the
traversing dial clamp. This clamp is actuated by the knurled head of the traversing dial clamp which
is located under the left lower surface of the tripod head. A zero index engraved on the left rear
quadrant of the pintle is utilized in conjunction with the traversing dial to establish or measure
horizontal angles.
e. The traversing bar provides a rear support for the mounted gun, the traversing block of the
elevating and traversing mechanism mating with the bar. An additional device for measuring or
establishing horizontal angles is incorporated in the scale engraved on the traversing bar. This scale
is divided into 100-mil major divisions and 5-mil minor subdivisions. It has a range of 444.5 mils to
the right and left.
Fig. 15. — Machine gun tripod M2.
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FM 23-45 Basic Field Manual
Fig 16. — Machine gun tripod M2 (schematic)
/ The traversing bar articulates in sliding sleeve devices at each end, the sleeves moving along the
trail legs in mounting and dismounting the tripod. Positioning stops are incorporated on the trail legs,
positively positioning the traversing bar in both the mounted and dismounted positions of the tripod.
The traversing bar sleeve latch, mounted on the right trail leg, secures the traversing bar in its proper
position when the tripod is mounted.
■44. DISASSEMBLING AND ASSEMBLING OF LIGHT MACHINE GUN TRIPOD M2.—
a. The disassembly and assembly of the parts of the light machine gun tripod are not essential
except to replace broken or damaged parts.
b. The front leg articulation with the tripod head, the rear leg articulations with the tripod head,
and the articulations of the traversing bar with its sleeves are standard commercial bolts with lock
washers and nuts to fit. Spare bolts, nuts, and washers are carried in the spare parts chest. All these
unions must be kept tight to insure accurate firing.
c. The pintle latch housing is secured to the tripod head by standard commercial cap screws and
suitable lock washers. Spare cap screw and washer and pintle latch spring are carried in spare parts
chest.
d. The traversing bar-sleeve latch is pivoted on the right trail leg by rivet assembly.
e. The pintle bushing is of bronze and is a pressed fit into the tripod head. It may be removed by
pressing it out and may be replaced by new bushing. Removal of the pintle bushing frees the
traversing dial. This disassembly is preferably done by Ordnance Department personnel.
f. The traversing dial clamping mechanism, seated in its recess in the tripod head, may be
removed by first removing the small hexagonal lock nut on the foot of the clamp, then the knurled
clamp nut. This permits the clamp being removed from the top of the tripod head. This disassembly
is preferably done by Ordnance Department personnel.
Section VII
ACCESSORIES
■45. PACK EQUIPMENT. — Sepcial pack equipment for use with the light machine gun
consists of -
1 tripod and gun hanger
1 ammunition hanger
3 ammunition chests
1 spare parts chest
1 gun cover, canvas
1 spare barrel canvas case.
■46. Hangers.—
a. Tripod and gun hanger. —
(1) This pack hanger is a light duralumin and steel hanger, accommodating the
tripod, the light machine gun, and the spare parts chest. It fits the standard Phillips
cavalry pack saddle and is carried on the right side, hung on the horizontal supporting
member of the saddle by steel reinforced hooks of the main supporting members of the
hanger and secured by to hold-down straps.
(2) The spare barrel canvas case with contents is habitually carried strapped to
the lower horizontal member of the hanger to balance the pack load laterally. The case
should be carried with the opening to the rear. When ammunition has been expended,
the case with contents may be strapped to the lower horizontal member of the
ammunition hanger on the left side to retain lateral balance of the pack load.
b. Ammunition hanger. — This hanger is of duralumin and steel construction,
accommodating three ammunition chests, and is habitually carried on the left side of
the standard Phillips cavalry pack saddle. The hanger is symmetrical longitudinally
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FM 23-45 Basic Field Manual
and may be used on either side of the Phillips cavalry pack saddle in case an extra
ammunition pack horse is utilized to transport ammunition for the light machine guns
of a horse cavalry organization.
■47. Chests.—
a. Ammunition chests. — The ground light machine gun is provided with ammunition
chest Ml which is constructed of light duralumin, lined with leather, equipped with a
leather carrying handle; normal capacity, two 150-round fabric belts (300 rounds).
b. Spare parts chest. — The light machine-gun spare parts chest is modified from an
Ml ammunition chest by the insertion of a partition accommodating one 150-round
fabric belt in one side and spare parts and accessories in the other. The authorized
contents of the spare parts chest are listed in SNL No. A-6.
■48. Covers.—
a. The gun cover is s small canvas cover provided to protect the working parts of the
gun in pack. It is removable without taking the gun out of pack and when so removed
may be placed in an ammunition chest.
b. The spare barrel canvas cover is designed to accommodate an assembled barrel
and barrel extension.
■49. Belt Loading Machine (fig. 17).—
a. General. — This machine is for the rapid loading of fabric (web) belts. It is normally
fastened to a table or bench while in use.
b. To fill a web feed belt with cartridges. —
(1) Fasten machine to a table or bench and turn crank (10) to the right until it is
straight down.
(2) Release tension spring hook (28) and raise upper feed wheel (18) as far as it
will go.
(3) Turn belt guide cover (56) to the right far enough to admit belt into belt guide
(53) and raise upper needle bar (45) as far as it will go.
(4) A black thread running along the side of the belt indicates the side for the
entrance of the cartridge. Put two cartridges by hand into the two loops of the belt
nearest the end with the brass tip, and place belt in machine with first cartridge
resting in top groove of lower feed wheel (22), belt passing out at back through belt
guide.
(5) Return belt guide cover to place over belt (being careful to see that the belt is
free to pass under it), and lower the needle bar.
(6) Turn upper feed wheel down upon belt and secure tension spring under hook.
(7) Fill feed guide with cartridges by stripping ten at a time from the paper boxes
in which they are packed.
(8) Turn crank to the right and the cartridges will be fed into the belt ready for use
in the gun.
(9) Place a feed box ready to receive the filled belt and at such a height that not
more than 2 feet of filled belt will be suspended from the feed wheels of the machine.
c. Precautions for using the belt loading machine for web belts. — (l) Before using the
machine, see that it is well oiled, all screws are tight, and that the needles are properly
set. See that the points of the upper needles are about 0.01 inch vertically above the
points of the lower needles.
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FM 23-45 Basic Field Manual
FIGURE 17. — Belt loading machine (web belts)
(2) In case of a miss in loading the belt, stop and open up machine and remove
belt. Turn crank to the right until straight down, as in starting, and replace belt in
machine with the next to the last cartridge in top groove of lower feed wheel. Close
machine and proceed as before.
(3) After use, the machine should be cleaned, oiled, adjusted, and replaced in its
wooden box.
■50. BLANK AMMUNITION ATTACHMENT (fig.18). — a. General. — The blank ammunition
attachments for use with the machine gun have been developed in order to simulate
fire. The attachments are designed to fire M1909 blank ammunition.
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FM 23-45 Basic Field Manual
FIGURE 18. — Blank firing attachments
(1) The cartridge stop attachment is inserted by withdrawing the belt holding
pawl split pin about V% inch and sliding the attachment over the cartridge stop, lining
up the small hole with the belt holding pawl split pin and replacing this pin. The
cartridge stop attachment acts as a guide for the blank cartridge and also as a
cartridge stop. Its chief use is to hold the cartridge in position in feedway so that the
extractor may engage its cannelure; it also prevents the entrance of a live round into
the feedway.
(2) The muzzle attachment is assembled to the gun by removing the front barrel
bearing, sliding the threaded end of the attachment over the barrel, and screwing it
into the barrel jacket.
b. Precautions. —
(1) Never attempt to use the muzzle attachment unless the cartridge stop
attachment is in its proper place in the feedway.
(2) Always remove the muzzle attachment before removing the cartridge stop
attachment in order to eliminate the possibility of firing ball ammunition with the
muzzle attachment still in position.
(3) See that the muzzle attachment is clean inside before using.
(4) After firing blank ammunition, clean the barrel and muzzle attachment. It is
absolutely essential that this be done before firing any other type of ammunition.
■51. SPARE BARREL. — A spare barrel is issued for each light machine gun. In pack, this
barrel is carried on the gun and tripod hanger.
■52. ASBESTOS MITTENS. — One pare of asbestos mittens (carried by the gunner) is
issued for use with each machine gun to facilitate the handling of the gun when hot,
particularly when moving to a new position by hand, and in changing barrels.
Section VIII
FIRE CONTROL INSTRUMENTS
■53. Field Glass, Type EE.—
a. Description. —
(1) The field glass, type EE (fig. 19), is an observation instrument of 6-power with
an 8° field of view. It contains a graduated mil scale for the measurement of small
horizontal and vertical angles. In field glasses of older manufacture there is also
provided an inverted sight leaf scale for the rapid computation of certain fire data. The
field glass complete consists of the glass and its carrying case and neck strap.
(2) The field glass proper consists of two compact prismatic telescopes pivoted
about a common hinge which permits adjustment for interpupillary distances. A scale
graduated every 2 millimeters from 56 to 74 permits the observer to set the telescopes
to suite his eye distance when the spacing of his eyes is know. The eyepiece can be
focused independently for each eye by screwing in or out. Each is provided with a
diopter scale for rapid setting when the observer knows the correction for his eye. The
zero graduations indicate the setting for normal eyes.
(3) The left telescope is fitted with a glass reticle (fig. 20) upon which are etched a
vertical mil scale, a horizontal mil scale, and on field glasses of over manufacture, a
stadia scale graduated similar to the sight leaf graduation on the service rifle, but
inverted.
b. Use. — The field glass is used for observations and the measurement of small
horizontal and vertical angles in mils. The inverted sight leaf, when provided, is used
to pick up auxiliary aiming points in direct layering.
c. Adjustments. —
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FM 23-45 Basic Field Manual
(1) Interpupillary distance. — To adjust the glass so that the eyepieces are the
same distance apart as the pupils of the observer's eye, point the glass at the sky and
open or close the hinged joint until the field of view ceases to be two overlapping circles
and appears to be one sharply defined circle, then note the reading on the scale, which
indicates the spacing of the observers eyes. The similar setting of any other field glass
will then accommodate his eyes.
(2) Focus of the eyepiece. — Look through the glasses, both eyes open, at an object
several hundred yards away. Place the hand over the front of one telescope and screw
the eyepiece of the other in or out until the object is sharply defined. Repeat this
operation for the other eye, then not the reading on each diopter scale. A similar
reading on any other field glass will accommodate the same eyes.
d. Operation. —
(1) In using the glass it should be held in both hands, lightly pressed to the eyes so
as to keep the relation with the eyes constant but not so as to transmit tremors of the
body. The bent thumbs may cover the corners of the eyes to exclude light except that
which enters the glass through the lenses. When possible, it is best to use a rest for the
glass or to rest the elbows on some solid object.
(2) The mil scales are seen when looking through the glass, and by superimposing
them on any objects the horizontal and vertical angles between those objects may be
read.
(3) The inverted sight leaf scale is used to secure range settings on sharply defined
auxiliary aiming points when the target is not clear enough for direct aiming.
e. Care. — The field glass is a rugged, serviceable instrument but it should not be
abused or roughly handles. Care should be taken not to scratch or mar the lenses.
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FM 23-45 Basic Field Manual
FM 23-45 Basic Field Manual
® On glasses of older manufacture.
On glasses of recent manufacture.
FIGURE 20. — Reticle on field glasses.
■54. WRIST WATCH. — The wrist watch is a timepiece of the usual construction supplied
with a strap for fastening to the wrist.
Section IX
INDIVIDUAL SAFETY PRECAUTIONS
■55. Precautions for Disassembling and Assembling Gun.— Paragraphs 12 and 13
outline the procedure for disassembly and assembly of the diring spring rod to the bolt.
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FM 23-45 Basic Field Manual
In order to avoid serious injury to personnel, the precautions outlined should be
carefully observed.
■56. Blank Firing Attachment. —
a. Never attempt to use the muzzle attachment unless the cartridge stop attachment
is in its proper place in the feedway.
b. Always remove the muzzle attachment before removing the cartridge stop
attachment in order to eliminate the possibility of firing ball ammunition with the
muzzle attachment still in position.
c. See that the muzzle attachment is cleaned inside before using.
■57. Hot Gun.—
a. To avoid serious burns, care must be exercised that the barrel and jacket are not
touched with bare hands. For moving the gun or disassembling a hot barrel, the
asbestos mittens should be used.
b. If the barrel becomes overheated after protracted periods of firing, the gun should
be cleared immediately on suspending or ceasing fire. The heat of the barrel will cause
the gun to fire without pulling the trigger, if a round is left a short time in the chamber
of an overheated barrel.
■58. SAFETY PRECAUTIONS ON THE RANGE.— Safety precautions for range firing are
included elsewhere in this manual and are not repeated here.
Section X
AMMUNITION
■59. General. — The information in this section pertaining to the several types of
cartridges authorized for use in the Browning machine gun, caliber .30, M1919A4,
includes a description of the cartridges, means of identification, care, use, and ballistic
data.
■60. Classification.—
a. Based upon use, the principal classification of the ammunition for this machine
gun is —
(1) Ball, for use against personnel and light materiel targets.
(2) Tracer, for observation of fire and incendiary purposes.
(3) Armor piercing, for use against armored vehicles, concrete shelters, and
similar bullet resistant targets.
b. Other types provided for special purposes are —
(1) Blank, for simulated fire.
(2) Dummy, for training (cartridges are inert).
■61. LOT NUMBERS. — When ammunition is manufactured, an ammunition lot number
which becomes an essential part of the marking is assigned in accordance with
pertinent specifications. This lot number is marked on all packing containers and on
the identification card enclosed in each packing box. It is required for all purposes of
record, including grading and use, reports on condition, functioning, and accidents in
which the ammunition might be involved. Only those lots of grades appropriate for the
weapon will be fired. Since it is impractical to mark the ammunition lot number on
each individual cartridge, every effort will be made to maintain the ammunition lot
number with the cartridges once they are removed from their original packing.
Cartridges which have been removed from the original packing and for which the
ammunition lot number has been lost are placed in grade 3. It is therefore obvious that
when cartridges are removed from their original packings they should be so marked
that the ammunition lot number is preserved.
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FM 23-45 Basic Field Manual
■62. Grade. — AR 775-10 explains the meaning of grading for caliber .30 ammunition.
Ordnance Field Service Bulletin No. 3-5 lists numerically every lot of ammunition with
its correct grade as established by the office of the Chief of Ordnance. Only lots of
proper grade will be fire. Grade 3 indicates unserviceable ammunition and will not be
fired.
■63. Identification.—
a. Markings. — The contents of original boxes are readily identified by the markins on
the box. Similar markings on the carton label identify the contents of each carton.
b. Color bands. — Color bands painted on the sides and ends of the packing boxes
further identify the various types of ammunition. The following color bands are used:
Cartridge, ball
Cartridge, ball , and cartridge tracer,
In metallic link belts. 1
Cartridge, tracer
Cartridge, armor piercing
Cartridge blank
Cartridge, dummy
Red.
Composite band of yellow, red,
and green stripes (yellow on left,
red in center, green on right).
Green on yellow.
Blue on yellow.
Blue
Green.
Special packing for Air Corps, not for use in the Browning machine gun, caliber .30, M1919A4
c. Types and models of caliber .30 cartridges. — When removed from their original
packing containers, the cartridges may be identified, except as to ammunition lot
number and grade, by physical characteristics described below :
(1) Ball. — All models of caliber .30 ball ammunition, except the M1906, have
bullets with gilding metal jackets. The jacket of the M1906 bullet is cupronickel which
has a silvery appearance. The gilding metal jacket of the M2 ammunition is tin coated
and hence resembles the M1906 bullet in appearance. The gilding metal jacket of the
Ml bullet is copper colored.
(2) Tracer. — Caliber .30 tracer ammunition may be identified by the nose of the
bullet which is painted red for a distance of approximately 14 inch from the tip.
(3) Armor Piercing. — All models of caliber .30 armor piercing ammunition may be
distinguished by the nose of the bullet which is painted black for a distance of
approximately 14 inch from the tip. The bullets have gilding metal jackets.
(4) Blank. — Blank ammunition may be identified by the absence of a bullet in the
cartridge case.
(5) Dummy. — The caliber .30 corrugated dummy cartridge may be identified by six
longitudinal corrugations and a hole in the cartridge case.
■64. Care, Handling and Preservation. —
a. Small arms ammunition as compared with other types is not dangerous to handle.
Care, however, must be observed to keep the boxes from becoming broken or damaged.
All broken boxes must be immediately repaired and careful attention given so that all
markings are transferred to the new parts of the box. The metal liner should be air-
tested and sealed if equipment for this work is available.
b. Ammunition boxes should not be opened until the ammunition is required for use.
Ammunition removed from the airtight container, particularly in damp climates, is apt
to corrode, thereby causing the ammunition to become unserviceable.
c. Protect the ammunition carefully from mud, sand, dirt, and water. If it gets wet or
dirty, wipe it off at once. Verdigris or light corrosion, if it forms on cartridges, should be
wiped off. However, cartridges should not be polished to make them look better or
brighter.
d. The use of oil or grease on cartridges is dangerous and is prohibited.
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FM 23-45 Basic Field Manual
e. Do not fire dented cartridges, cartridges with loose bullets, or otherwise defective
rounds.
f. Do not allow the ammunition to be exposed to the direct rays of the sun for any
length of time. This is liable to effect its firing qualities seriously.
g. No caliber .30 ammunition will be fired until it has been positively identified by
ammunition lot number and grade as published in the latest revision or change to
Ordnance Field Service Bulletin no. 3-5.
■65. Storage. —
a. Whenever practicable, small arms ammunition should be stored under cover. This
applies particularly to tracer ammunition which is subject to rapid deterioration if it
becomes damp. It may even ignite spontaneously. Should it become necessary to leave
small arms ammunition in the open, it should be raised on dunnage at least 6 inches
from the ground and the pile covered with a double thickness of paulin. Suitable
trenches should be dug to prevent water flowing under the pile.
b. If practicable, tracer ammunition should be stored separately from other
ammunition.
c. If fired into or placed in a fire, small arms ammunition does not explode violently.
There are small individual explosions of each cartridge, the case flying in one direction
and the bullet in another. In case of fire it is advisable to keep those not engaged in
fighting the fire at least 200 yards from the fire and have them lie on the ground. It is
unlikely that the bullets and cases will fly over 200 yards.
■66. BALLISTIC DATA. — The approximate maximum ranges and average velocities and
the several types of models of caliber .30 ammunition authorized for use in the machine
gun, caliber .30, Browning, M1919A4, are shown below :
Type and model of caliber .30 cartridges
Average
velocity 78
feet from
muzzle
(feet per
second)
maximum
Approxi-
mate
range
(yards)
Ball, M2
Ball, Ml
Ball, M1906
Tracer, Ml
Armor piercing, M2
Armor piercing, Ml
Armor piercing, M1922
Blank, M1909
Dummy, M1906 (Corrugated)
2,630
2,600
2,640
!2,650
2 2,730
!3,260
2,600
3,450
5,500
3,450
3,450
4,500
4,000
4,400
20
1 Approximate.
2 At 53 feet from muzzle
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FM 23-45 Basic Field Manual
ARMOR PIERCING-BLACK
CAL..30 ARMOR PIERCING AND TRACER CARTRIDGES
M 1906- CU PRONICK EL
MS-GILDING METAL
CAL.30 BALL CARTRIDGES
CARTRIDGE, BLANK, CAL..30.MI909.
FIGURE 21— Caliber .30 cartridges.
Document Prepared by James Jones (Teps7l)
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