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|  MIL-P-85662(AS)
3.1.1 Air space. The propellant charge weight that is required to
achieve the ball istic requirements of 3.2 and that conforms to the require-
ments of Drawing 1397AS190 shall result in an air space in the primed -
cartridge,case, which shall permit the insertion of the API projectile into
the charged case without any vibration or tamping to cause compaction of
the propellant charge.
Unless otherwise specified in the contract or
3.1.2 Nitrocellulose.
purchase order (see 6.2.1), nitrocellulose recovered from the rework of
propellants or new nitrocellulose with the nitrogen content not fully
meeting the requirements of MIL-N-244 may be used in lieu of, or in
combination with, complying nitrocellulose. Propellant so manufactured
shall comply with all chemical, physical, and ball istic requirements.
3.2 Internal ballistic performance. The propellant's internal bal-
listic performance shall be sampled as specified herein when loaded into
representative API Cartridges conforming to Drawing 1397AS190 and fired
in the approved specified GAU-12/U single-shot barrel and test fixture.
3.2.1 Muzzle velocity. The average muzzle velocity of the sample
cartridges, conditioned at 18 to 24 degrees Celsius (C), shall be not
less than 1,000 meters per second (m/s). The sample standard deviation
(see 6.4) shall not exceed 10 m/s. At any cartridge temperature from -54
to 71"C, the projectile muzzle veloclty shall be greater than 950 meters
per second.
3.2.2 Pressure. The average chamber pressure of the sample car-
tridges, conditioned at 18 to 24C plus three standard deviations of
chamber pressure, shall be not greater than 425 megapascals (MPa). The
average chamber pressure of the sample cartridges, when functioning at
any individual temperature from -54 to +71C plus three standard devia-
tions of chamber pressure, shall be not greater than 476 MPa. Pressure
shall be measured with a piezoelectric type pressure transducer or
equivalent.
3.2.3 Action time. The action time of the sample cartridges shall be
not greater than 6.0 milliseconds (ins) at any cartridge temperature from
-54 to 71c.
3.2.4 Special action time. The action time requirement of 3.2.3 shall
also be achieved with the propellant in the "powder-to-bullet" orienta-
tion with the ammunition conditioned at -54C. A charge weight 3 grams
below the established charge weight shall be used.
3.3 Flame temperature. The propellant shall have an isochoric flame
temperature of not greater than 2,800 Kelvin (K) as determined by the
Hirschfelder method of calculation.
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