M16 Maintenance Manual TM9-1005-319-23.pdf - CombatRifle.net

Table 3-1. 5.56MM Rifle M16A2, M4/M4A1 Carbine - Cont
ARMY TM 9-1005-319-23&P
AIR FORCE TO 1 l1W3-5-5-42
Bolt carrier group
Item
Bolt locking lugs and bolt
cam pin hole
Standard
Inspect bolt for elongated or oversized firing pin hole using plain
cylinder gage 12620101.
Firing pinholes which permit the plain cylinder plug gage to fully
penetrate at any position on the circumference will be rejected.
Bolt face with a cluster of pits which are touching or tightly grouped,
covering an area measuring approximately 1/8 inch (0.31 cm)
across will be rejected.
Bolts which contain pits extending into the firing pinhole will not be
rejected unless firing pin hole gaging check determines
rejection.
Bolts which contain individual pits or scattered pits will not be
cause for rejection.
Only phosphated bolt carriers are acceptable. Both phosphated and
chrome plated bolts are acceptable.
Inspect for cracks in the locking lugs and cam pin hole area. Use
a black light, if available; otherwise, use a glass of no more than
3X magnification or use inspection penetrant (item 25, app D).
Use instructions contained in kit for application. If cracks are
detected, the bolts will be replaced.
NOTE
Particular attention must be given to the area where
the lugs meet the bolt body and around the side walls
of the cam pin hole.
Bolt rings must not be broken. Ring gaps must be properly spaced
approximately 1/3 turn apart and not in line.
Firing pin protrusion must be not less than 0.028 inch (0.071 cm)
or more than 0.036 inch (0.091 cm). (Use firing pin protrusion
gage 7799735.)
Socket head capscrews must be staked.
Carrier key must not be dented where end mates with gas tube.
Repair or replace damaged carrier keys.
Headspace
Inspect headspace using headspace gage 7799734. Excessive
headspace will be cause for rejection.
Trigger pull Inspect trigger pull using trigger measuring fixture 7274758.
Trigger pull must be minimum 5.5 pounds (2.49 kg), maximum
for M16A2 and M4 is 9.5 pounds (4.31 kg) and
maximum for M4A1 is 8.5 pounds (3.86 kg). Test trigger
pull, refer to page 3-83, steps a, b, c, and d.
Change 4 3-101