4.6.5 Sear release disengagement test. The gun shall be tested
with the gun held in a horizontal position. The hammer shall be in the
released position, and the firing rod shall be fully forward under spring
action. The travel of the firing rod from the point where the firing
rod slack is taken up to the point where the sear release disengages the
sear shall be measured using the inspection equipment in accordance with
4.6.6 Hammer release and spring return load tests. The gun shall
be tested with the gun or firing mechanism in a horizontal position.
The hammer shall be in the cocked position when the load required to re-
lease the hammer from the sear is applied and measured. The hammer shll
be in the released position with the firing mechanism attached to the
gun or, the hammer shank shall be 90 5 from the top of the firing
mechanism housing with the firing mechanism detached fron the gun when
the spring force returning the firing rod from the fully retracted posi-
tion to engage the sear release with the sear is measured. Inspection
equipment in accordance with Drawing D7270711 shall be used.
4.6.7 Firing pin indent test. The gun shall be tested with the gun
held In a horizontal position. The prescribed copper compression
cylinder shall be inserted in the recess of a holding fixture in accor-
dance with Drawing D7270710 and the holding fixture inserted in the
barral chamber while the bolt is held open. The bolt shall be manually
returned to battery position and the firing rod pulled to release the
firing pin. The holding fixture shall be removed from the gun and the
depth of the indent in the copper compression cylinder computed by
measuring the distance from the original surface of the cylinder (before
indentation) to the bottom of the firing pin impression. The firing pin
indent impression shall be visually examined to determine whether the
concentricity and indent requirements have been met.
4.6.8 Endurance test.
18.104.22.168 Guns shall be tested using a contractor designed, govern-
ment approved mount.
22.214.171.124 Firing shall be single shots, deliberately spaced at
approximately 2 second intervals, in series not to exceed 100 rounds
using fully loaded magazines. The magazines shall be used in rotation
so that approximately 500 rounds will be fired from each magazine.
126.96.36.199 The barrel shall be cooled to ambient temperature by air
after each series. The guns shall have been lubricated as specified
below at the beginning of the test and cleaned and lubricated after each
500 rounds and at the close of each day's firing. No other cleaning
and lubrication shall be performed during this test. No parts shall be
altered or replaced during cleaning except that parts broken or worn to
the extent that they are unserviceable shall be replaced.