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Chamber pressure, velocity and action time. |
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|  MIL-C-70725A (AR)
(Bubble test), Test in accordance with
4.6.4 Waterproof.
SCATP-5.56mm, Chapter 1, Section 14. If the cartridge fails the
bubble test, the velocity/waterproof test may be used.
4.6.5 Velocity/ waterproof. This test may be substituted
for the bubble test. The cartridges shall be submerged in water
at +20C, for 24 hours, wiped dry, then placed in a temperature
controlled room or chamber at +20 2C for at least two hours.
Fire the cartridges one shot at a time in a universal receiver,
recording the velocity at 15 feet in accordance with SCATP-
5.56mm, Chapter 1, Section 13. Failure to meet the requirement
shall be grounds for rejection.
4.6.6 Chamber pressure, velocity and action time. The test
samples shall be conditioned at the test temperatures, 2C for
at least two hours. The test shall be conducted in accordance
with SCATP-5.56mm (Heavy Bullet), Section 7, except that Port
pressure need not be measured and the firing of reference
cartridges shall be conducted only to qualify test barrels (range
and equipment corrections will be applied to test results). For
Qualification and First Article Inspections, testing at +20C,
-20C and +50C shall be divided equally among three 1 in 7-inch
and three 1 in 12-inch twist barrels. Testing at +68C and -50C
shall be divided equally among one (1) in 7-inch and one (1) in
12-inch barrels. For lot acceptance inspection, testing shall be
divided equally among two, 1 in 7-inch and two 1 in 12-inch
barrels. For acceptance, the average of the results in each
barrel type shall meet the applicable requirements. Action time
shall only be recorded in one barrel of each type, at each test
temperature.
4.6.7 Dispersion. The test shall be conducted in
accordance with SCATP-5.56mm, Chapter 1, Section 3 with the
following amendments:
a. The rounds shall be tested in both a 1 in 12-inch
twist accuracy barrel, and a 1 in 7-inch twist accuracy barrel.
Three (3) barrels of each type shall be used.
b. Equipment lists for dispersion testing can be
found in ARDEC drawings 8654126 and 8649433.
Ten-round targets shall be fired with the targets
located 25 meters from the muzzle of the test barrel. The target
shall be of a size applicable to the expected dispersion of the
bullet holes.
34
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