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| MIL-C-14858A (AR)
AMENDMENT 3
APPENDIX A
in an insulated box (five cartridges at a time) which has been conditioned at the required
temperature and the box placed at a point convenient to the technician. The cartridges shall then
be removed singly from the insulated box immediately before firing. If an insulated box is not
available, the cartridges shall be removed singly from the temperature controlled room or box
immediately before firing.
A.7.3 In order that the propellant shall be uniformly positioned from cartridge-to-
cartridge, attention to detail is necessary in handling and chambering the cartridges. The
cartridge shall first be held vertically, bullet upward. It shall then be rotated slowly in a vertical
plane, stopping the rotation momentarily after 1800 of rotation when the bullet is downward and
then continuing throughout the remainder of the 3600, stopping when the cartridge is again bullet
end upward. The bullet end of the cartridge should now be lowered slowly to a position slightly
above horizontal and chambered very carefully, taking care that the primer end of the case is not
elevated above the bullet end of the case. (The object is to have the cartridge seated in the
chamber ready to fire, with the propellant in a loose condition at the primer end of the case, and
with such airspace as is present at the bullet end of the case.)
A.7.4 The breechblock is closed gently. If the technician encounters any difficulty
closing the breech block or engaging the trip lever, the test shall be discontinued until such
difficulty is corrected. If any delay should occur after the cartridge is placed in the chamber and
the duration of the delay is approximately 30 seconds or longer, the cartridge shall be extracted
and another cartridge inserted in its place.
A.7.5 The trip lever to which the lanyard is attached shall be engaged with the hammer.
The technician shall retire to a safe position and pull the lanyard with a smooth, firm motion.
The action time, velocity, peak chamber pressure of the shot shall be recorded. The breech block
shall be opened, the fired case extracted and visually inspected by the technician to possible
casualties.
A.7.6 The procedure prescribed in 6.3 through 6.5 shall be repeated until the required
number of reference cartridges has been fired.
A.7.7 Continuous air cooling should be used on the barrel. If air cooling is not
available, the barrel shall be allowed to cool to ambient temperature between each series of tests,
or after a maximum of 20 cartridges has been fired. At no time shall the exposed metal surface
of the test barrel become too hot to grasp with the bare hands (approximately 1400F).
A.7.8 The velocity and pressure corrections shall then be obtained as prescribed in 3.3.
A.7.9 If the mean velocity, chamber pressure or port pressure obtained for the reference
cartridges is not within the limits permitted, the test barrel shall be removed from the test,
another barrel substituted and another series of reference cartridges fired. If this firing fails to
produce satisfactory mean velocity, chamber pressure or port pressure values, the cause thereof
shall be identified and eliminated before resuming the test.
8 (24)
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