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|  MIL-C-63990C (AR)
3.9.2 Day test. The bullet of the tracer cartridge shall
exhibit ignition of the trace when fired from both the M249
machine gun and M16A2 rifle.
3.10 Temperature stability. The action time, pressure and
velocity of sample cartridges conditioned and fired at the
temperature extreme specified below shall be in accordance with
3.10.1, 3.10.2, 3.10.3 and 3.10.4.
a. Conditioned at 125 2F for not less than one
hour and fired at that temperature.
b. Conditioned at -65 2F for not less than one
hour and fired at that temperature.
3.10.1 Velocity. The average velocity shall not decrease
by more than 250 fps with respect to the average velocity of the
sample cartridges conditioned at 70 2F. Any increase in
velocity is acceptable.
3.10.2 Chamber pressure. The average chamber pressure
shall not vary from the average chamber pressure of the sample
test cartridges conditioned to 70 2F by more than 7,000 psi.
The average chamber pressure of the sample cartridges conditioned
at 125 2F shall not exceed 60,000 psi. Any deecrease in
chamber pressure is acceptable.
3.10.3 Port Pressure. The average port pressure shall not
vary by more than 1,500 psi from the average port pressure of the
sample test cartridges of the same lot conditioned at 70 2F,
and shall not be less than 11,400 psi.
3.10.4 Action time. The mean action time for these
cartridges shall be as stated in 3.15.
Both the average vertical standard
3.11 Accuracy
deviation and the average horizontal standard deviation shall be
no greater than 10.3 inches at 600 yards.
3.12 Function and casualty. The cartridge shall function
without casualty at ambient temperature and under the temperature
conditions specified below in both the M249 machine gun and M16A2
rifle.
a. Conditioned at 125 2F for not less than one
hour and fired at that temperature.
b. Conditioned at -65 2F for not less than one
hour and fired at that temperature.
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