MIL-DTL-70599C
indent, muzzle down position indent and firing pin indent position.
3.6.1.2 Bolt action indent. When the bolt is closed and the firing mechanism is released,
the firing pin indent shall not be less than 0.020 inches.
3.6.1.3 Muzzle down position indent. When in a muzzle down position, the bolt carrier
assembly shall be released from the full recoil position and the firing mechanism shall not be
actuated, the firing pin indent shall not be greater than 0.008 inches.
3.6.1.4 Firing pin indent location. The firing pin indent shall not be off-center more than
one half the maximum diameter of the indent.
3.6.1.5 Firing pin protrusion. The firing pin protrusion shall not be greater than 0.036
inches and shall not be less than 0.028 inches.
3.6.2 Trigger pull.
3.6.2.1 Minimum trigger pull. The minimum trigger pull shall not be less than 5.5
pounds when checked with the burst disconnect in a deep notch of the burst cam.
3.6.2.2 Maximum trigger pull. The maximum trigger pull shall not be greater than 9.5
pounds when checked with the burst disconnect in a deep notch of the burst cam.
3.6.2.3 Creep. The M4 trigger shall be free of perceptible rough movement between the
time the trigger slack is taken up and the hammer is released.
3.6.3 High pressure resistance.
3.6.3.1 High pressure resistance test. The barrel assembly in accordance with drawing
9390009 and bolt in accordance with drawing 8448510 shall withstand the firing of one M197,
5.56mm high pressure test cartridge in accordance with drawing 10533839 or commercial
equivalent conforming to SAAMI-Z299.4 specifications. Unless otherwise specified, the barrel
assembly and bolt shall be tested concurrently.
3.6.3.2 Headspace. After the high pressure resistance test, each weapon shall be gagged
to meet headspace requirement after proof firing.
3.6.3.2.1 Minimum headspace. After the high pressure resistance test, the headspace
shall not be less than 1.4646 inches when measured to the 0.330 inches datum diameter on the
first shoulder of the chamber.
3.6.3.2.2 Maximum headspace. After the high pressure resistance test, the headspace
shall not be greater than 1.4706 inches when measured to the 0.330 inches datum diameter on the
first shoulder of the chamber.
3.6.3.3 Barrel assembly integrity. After the high pressure resistance test, the barrel
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