19. Disassembly
a. General. Remove and disassemble barrel and receiver groups
(figs. 24 and
25) as outlined in FM 23-5.
b. Removing Barrel From Receiver (fig. 26). The barrel should be
removed from the receiver only when rebarreling is necessary and then only
by fifth echelon organizations. To remove, pass the barrel into the
fixture, muzzle end first, until rib on barrel stops against shoulder in
fixture. Position wrench on receiver as near to the barrel as possible and
unscrew the receiver (counterclockwise) from the barrel.
Note.
Never place the wrench on the rear of the receiver, as this will cause
distortion.
c. Follower And Slide Assembly. Disassemble follower and
follower slide (fig. 24) only when repair or replacement of parts is
necessary. If necessary to disassemble, insert the blade of a screw driver
under the front end of the slide (fig. 27) pry upward and forward,
unlocking slide from follower.
d. Gas Cylinder group. (1) Front sight screw. Loosen
the front sight screw (fig. 25) before attempting to remove the gas
cylinders which have been modified, that is, those having a cut extending
from the front sight base dovetail downward to the lower splines. Unless
the front sight screw is loosened, damage may result to the barrel and gas
cylinder. The front sight screw may be so tight that binding action of the
gas cylinder on the barrel will make it difficult to remove the gas
cylinder by lightly tapping on the bayonet lug (as prescribed in FM
23-5).
(2) Front sight screw seal. To remove the front sight screw seal
(fig. 25), file off its exposed surface, and with a 3/16-inch hexagonal
socket head set screw wrench, back out the screw. Replace and tighten the
screw.
Note. The seal is no longer required and is not to be replaced
after it has once been removed.
(3) Gas cylinder lock. Gas cylinder locks which are extremely
tight fitting may be removed by use of the gas cylinder lock assembling
wrench. Fit wrench over contour of gas cylinder lock and unscrew
(counterclockwise). (See fig. 28)
e. Removing And Installing Extractor Without Removing Bolt From
Rifle (fig. 29). To remove or install the extractor without removing
the bolt from the rifle proceed as follows, using bolt, wire brush, and
screw driver combination tool:
(1) Retract the bolt and insert the wire brush into the chamber of the
barrel until the shoulder bears against the breech end of the barrel.
(2) Allow the bolt to close slowly, turning the tool so that the lug is
under the extractor.
(3) Force the operating rod forward, holding the bolt against the tool,
and turn the combination tool counterclockwise so that the lug pushes the
extractor out of its seat and out of engagement with the ejector.
(4) Retract the bolt slowly, thus allowing removal of the extractor spring
plunger assembly and the cartridge ejector assembly. The firing pin can
then be withdrawn from its well.
(5) To install, place ejector and ejector spring, extractor and extractor
spring in the bolt. With the brush of the combination tool in the chamber,
line up the notches of the firing pin and ejector and force the operating
rod forward, compressing the ejector spring. While holding spring
compressed, press extractor into position.
20. Inspection
a. General. Inspect all parts
for damage, wear, burs, rust, foreign matter in recesses, deformation, and
for function and free action with mating parts. Important points to be
inspected are shown in figures 30 and
31. Test all springs for set,
minimum free length, and fracture.
b. Follower Rod. Inspect follower rod (fig. 31) for a
pinched or worm fork and for loose rivets. The follower rod should have a
long fork; therefore, replace all rods having short forks. (See
fig. 32)
This is necessary to prevent the rod from disengaging when grenades are
being launched, Dispose of the old type (short fork) follower rod in
accordance with existing regulations for unserviceable equipment.
c. Operating Rod Spring. (fig. 24) Inspect the operating rod
spring for free length and load in the following manner, using operating
rod spring gage:
(1) Testing free length. Insert the operating rod spring in the
tube of gage and raise rod until bottom of stop collar is flush with the
top surface of gage. (See fig. 33) Note position of operating rod spring
in regard to top face of tube. If spring does not protrude beyond top face
of tube, the maximum free length of 20 1/4 inches is satisfactory and the
spring is serviceable in regard to free length. With the spring still in
the tube, allow the rod to return to its original position and test for
load.
(2) Testing load. Insert the stem of the 5-pound weight in the tube
of gage and allow its weight to compress the spring. It should compress
between 16 3/4 and 17 3/4 inches which is indicated by the first 1-inch
relief notch cut in the stem of the weight. Note position of this notch in
regard to top face of tube. If top face of tube falls within limits of the
relief notch (fig. 34), the load at 5 pounds is acceptable. Next position
the 11-pound weight on top of the 5-pound weight and allow their combined
weight to compress the spring. It should compress between 11 3/4 and 12
3/4 inches which is indicated by the second 1-inch long relief notch cut
in the stem of the 5-pound weight. Note position of this notch in regard
to top face of tube. If top face of tube falls within the limits of the
notch (fig. 34) the load at 16 pounds is acceptable.
d. Operating Rod (fig. 30). Inspect for binding between the
barrel and receiver group and the operating rod by installing the rod and
bolt in the rifle. As the rifle is tipped up and down, the rod and bolt
should be moved from closed to open position and back by their own weight.
If there is binding, inspect tube for dents and the handle for
deformation, which will cause binding of the under side of the lug on the
cut in the receiver. Inspect the diameter of the piston using no-go piston
gage. (See fig. 35) All no-go piston diameter gages, initially produced
are being withdrawn from service for reworking since the dimension of
these gages has proven unsatisfactory. Pending the correction of these
gages, the piston diameter will be measured with a micrometer and pistons
which measure 0.525 inches or more should be considered serviceable. If
the piston diameter is below the minimum specified by the serviceability
chart (fig. 23), the operating rod assembly should be disposed of as
unserviceable and uneconomically reparable, since an undersized gas piston
tends to reduce the power available to operate the weapon.
e. Follower And Follower Slide (fig. 30). Inspect slides on
follower for correct angle. An angle of approximately 92°
plus/minus 0° 20 minutes must be
maintained. (See fig 36)
f. Rear Sight Pinion - Early Manufacture. Inspect the
pinions visually. Pinions having cracks caused by staking will not be
removed from service (fig. 37), provided they do not interfere with
functioning.
g. Gas Cylinder Group (fig. 38). Check the inside diameter
of gas cylinder with gas cylinder gage. When the threads are cut in the
gas cylinder the metal tends to flow and the inside diameter of the
threaded section is reduced; therefore, this section must be slightly
reamed to allow the gage to be inserted. Use the reamer on one end of the
gage to perform this operation. Only the wire edge on top of the threads
is removed. Remove all chips after reaming; any chips remaining will cause
galling between the gas cylinder and the gas cylinder lock screw, due to
the nature of stainless steel. Insert the gage after reaming and if the
cylinder is serviceable the index surface of the gage should be level
with, or protrude above, the end of the gas cylinder. (See
fig. 39)
Caution: No force must be applied to a gage when a
cylinder is being checked. If the gage is forced in the cylinder and
rotated it will act as a reamer and will render the gas cylinder
unserviceable.
Insert a small rod in the screw driver end of the gas cylinder lock
screw and raise the valve from its seat. Inspect for burs and foreign
matter. This is an important check as gas allowed to escape through the
valve will dissipate the force necessary to drive the operating rod to the
rear, thus causing a short recoil malfunction. Inspect function of valve
spring to see that it closes the valve tightly in its seat. Replace all
gas cylinder lock screws which have burs on the valve face or seat, or
where the spring tension is insufficient to seat the valve tightly. All
gas cylinder lock screws of early manufacture should be replaced by gas
cylinder lock screw with valve assembly.
h. Bolt Assembly (fig. 40). (1) Bolt. Test the bolt
while it is free for freedom and smoothness of movement, and for locking.
(2) Firing pin. Check protrusion of firing pin beyond the face of
the bolt using firing pin protrusion gage. (See
fig. 41) In fired
position, the nose of the pin should protrude from 0.044 inch minimum to
0.059 inch maximum. Remove all full round firing pins and discard in
accordance with existing regulations.
(3) Extractor. Test the extractor for grip of the cartridge base,
and the extractor spring for tension.
i. Barrel. Inspect the barrel as outlined in
section II.
j. Telescope Mount And Bracket (U.S. Rifle, Cal. .30, M1C
(Sniper's) Only) (figs. 42 and
43). Inspect telescope mount bracket
for retention on receiver and for burs on male dovetail slides. Inspect
slide for function in telescope mount bracket and locking action of slide
clamp with locking screws. Check supports for looseness in slide. Inspect
screws and screw holes for worn or stripped threads and all recesses for
foreign matter.
k. Telescope Mount And Base (U.S. Rifle, Cal., .30, M1D (Sniper's)
Only) (fig. 44). Inspect base for looseness on barrel, and for burs.
Inspect dowel pin for burs, wear, and for looseness in base. Inspect knob
for looseness on screw and for worn knurling. Inspect function of plunger
and spring with knob. Inspect all screws and screw holes for stripped or
worn threads. |
