MIL-DTL-19264C (OS)
4.6.6.3.3 Matching Charge Evaluation. A linear, least squares equation shall be calculated for the
velocity-charge data for each gun. The MC is determined by substituting the required velocity in the
linear least squares equation and solving for the charge weight. Three (3) MC rounds are fired in each of
the four (4) guns to determine the MC projectile muzzle velocity.
4.6.6.3.4 Assessed Charges. The assessed charge (AC) shall be determined by using the formula:
⎛ MCi ⎞
4
∑⎜ Δ 2 ⎟
⎟
⎜
⎠
i=1 ⎝
AC =
i
4⎛
1 ⎞
∑⎜ Δ ⎟
⎜ 2⎟
i=1 ⎝ i ⎠
where: MCi = charge weight of the test propellant estimated to match the mean RP projectile velocity in
the ith gun.
Δi = difference between the mean muzzle velocity obtained for the matching charge in the ith gun
(MCi) and the mean RP projectile muzzle velocity in the ith gun. Note: If Δi is zero, replace the
zero with 1.
4.6.6.3.5 Charge Weight Validity. The validity of the assessed charge shall be determined by a firing
program in any of the gun barrels used in the powder proof firings from the instrumented test mount using
cases instrumented with piezoelectric gauges to obtain breech pressure measurements. The program shall
consist of ten (10) RP rounds and ten (10) TP rounds which have been assembled and preconditioned as
noted 4.6.6.3 except that adhesive, in accordance with drawing 3208375, shall be used on the closure plug
and allowed to cure. The rounds shall be randomized to eliminate any gun erosion or hot gun effect.
Velocity measured in this test is for information only. The mean chamber pressure and chamber pressure
standard deviation shall meet the requirements of 3.8.2 and 3.8.4 respectively or the lot shall be rejected.
4.7.6.4 Velocity Uniformity. The velocity standard deviation shall be determined from the matching
charge data obtained from each gun barrel. The velocity standard deviation shall meet the requirements
of 3.8.3 or the lot shall be rejected. To calculate the velocity standard deviation, perform the calculations
described in a though d.
a. Calculate the sum of the squares of the deviations from the mean for each gun barrel.
b. Sum across the gun barrels.
c. Divide by the quantity of the sum of the total number of rounds minus the number of guns.
d. Take square root to nearest unit of acceptance criteria.
4.6.7 Examination of packaging. Each unit of packaging shall be visually examined for conformance
to the requirements of Section 5.
4.6.8 Relative quickness. Relative quickness of the propellant shall be conducted via closed bomb test
as specified in MIL-STD-286, Method 801.1.2. The closed bomb reference propellant shall be
representative of the nominal composition of the propellant type to be tested (preferably the RP used for
ballistic acceptance testing). The "hot-wire" method of ignition may be used as an alternative to the
"squib" method.
4.6.9 Interface tests. The procedure is described in the note (see 6.5). For the first article lot the test
is mandatory. For production lot, the test shall be performed at the discretion of the Government: (1)
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