18.104.22.168 Ammunition and links (see 6.2).
Unless otherwise specified in
procurement documents, the Government standard 7.62mm, M60 High-
Pressure Test Cartridge (MIL-C-46477) shall be used for the high
pressure resistance test; the 7.62mm, M80 Ball Cartridge (MIL-C-
46931) linked with the M13 Link (MIL-L-45403) shall be used for
all other firing tests; and the M172 Dummy Inert Loaded Cartridge
(MIL-D-60573) linked with the M13 Link shall be used as required
in the functioning firing test to separate belts of linked M80
The Government standard 7.62mm, M13 Link
(MIL-L-45403) shall be used for linking ammunition required for
4.5.1 Headspace test. Each machine gun with both its
assigned and spare barrel assembly with biped assembly shall be
gaged for headspace requirement (see 3.4.1) before and after high
pressure resistance firing, prior to acceptance, in accordance
with instructions specified on drawing 7274136 using the
inspection equipment conforming to drawing 7274515 and 7274459.
4.5.2 Firing pin indent test Each sample machine gun with
both its assigned and spare barrel assembly with biped assembly
shall be tested for firing pin indent requirement (see 3.4.2)
using the inspection equipment in accordance with drawing 7274381
The machine gun shall be cocked and then held in a
horizontal position with the cover assembly opened.
fixture containing the copper compression cylinder (8440920)
shall be inserted unto the barrel chamber, the cover closed, and
the trigger pulled to release the bolt and indent the copper
The holding fixture shall be removed from the machine
gun and the depth of the indent in the copper cylinder computed
by measuring the distance from the original surface of the copper
cylinder (before indentation) to the bottom of the firing pin
If any firing pin indent is not within the require-
ments, three more impressions shall be taken and the average
depth of the three indents of each test shall be calculated to
determine whether the requirement has been met.
shall be visually examined to determine whether the concentricity
requirement has been met.