Technical data

TM 9-1005-319-23&P 0029
0029-7
Table 1. 5.56mm Rifle M16A2/M16A3/M16A4, M4/M4A1 Carbine - Continued.
Item Standard
Bolt locking lugs and bolt pin
cam hole. ............................... 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. Use instructions contained in inspection
penetrant 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 in. (0.071 cm) or more than
0.036 in. (0.091 cm). Use firing pin protrusion gage 7799735.
Socket head cap screws 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 5.5 lb (2.49 kg) minimum. Maximum for M16A2, M16A4 and M4 is
9.5 lb (4.31 kg). Maximum for M16A3 and M4A1 is 8.5 lb (3.86 kg). Test
trigger pull (see WP 0009).
Lower receiver group............. Inspect hammer and trigger pin holes using plain cylinder plug gage
12006472. Penetration of the gage in any one or more of the four holes will
be cause for rejection.
Inspect for cracks, corrosion, or mutilation which would affect functioning.
Small dents or gouges will not be cause for rejection.
Inspect receiver for corrosion in the lobes of the pivot or hinge pin area.
Width between lobes shall not exceed 0.515 in. (1.30 cm).
Inspect receiver for break through of metal.
Inspect receiver and receiver extension for initial loss of protective coating.
NOTE
Lower receivers without pivot pin detent may be used
for all Air Force mission requirements.
Action spring ........................... M16A2/M16A3/M16A4 Rifle only:
Free length of spring shall be between 11-3/4 and 13-1/2 in. (29.84
and 34.29 cm).
M4/M4A1 Carbine only:
Free length of spring shall be between 10-1/16 and 11-1/4 in.
(25.56 and 28.58 cm).