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MIL-C-14858A (AR)
AMENDMENT 3
the same manner as in the first day and in accordance with the same criteria; (2) for each 20
round test the average velocity and standard deviation of the velocities shall be recorded; (3)
also, the daily average velocity (20 rounds in each of eight assemblies) and the Grand Average
of the entire series (5 assemblies x 3 days) shall be computed and entered in the Cartridge Lot
Acceptance Record (DD250)."
PAGE 16
*
4.5.6, Delete in its entirety and substitute the following:
"4.5.6 Chamber pressure.
4.5.6.1 Pre-conditioning and choice of test methods. Prior to chamber pressure testing,
cartridges shall be conditioned at 70F 2 F for a minimum of two hours. The test shall be
conducted in accordance with TECP 700-700, Vol. III when using the copper crush cylinder
method, and in accordance with Appendix D of SCATP - 7.62mm when using the EPVAT
method."
4.5.6.2 Selection and "breaking-in" of chamber pressure barrel assemblies. The five
chamber pressure barrel assemblies - specified in Ordnance Proof Manual (OPM) 7-12, Sect
2.1(2)b (of the TECP) shall be selected from a quantity of eight candidate barrel assemblies.
Prior to the firing of 30 reference cartridges through each of the eight candidate barrels - as
described in the next sentence - each of the eight candidate barrels shall be "broken in" by
firing 100 standard ball cartridges through them. (ONCE BROKEN IN, THE BREAKING IN
PROCESS SHALL NOT BE REPEATED.) Selection of the five chamber pressure barrels to
be used as described in 4.4.6.3 below, shall be made by firing 30 reference cartridges through
each of the eight candidate barrels and then selecting out those five (out of eight) barrels
having the lowest standard deviation for chamber pressure.
4.5.6.3 Testing procedures. First of all, there shall be three test cycles, one test cycle on
each of three succeeding days. FIRST DAY: (1) twenty reference cartridges shall be fired in
each of the five selected-out barrel assemblies; (2) the average velocity and standard deviation
of the chamber pressures for all five (20 round) firings shall be recorded. THEREAFTER, ON
TWO SUCCESSIVE DAYS, using the same five chamber pressure barrel assemblies: (1) an
additional 20 cartridges shall be fired each barrel; (2) the average chamber pressure and
standard deviation for all five barrels shall be recorded; (3) at the end of the third day, the
Grand Average chamber pressure and standard deviation for the entire series (5 assemblies x 3
days) shall be computed and entered in the Cartridge Lot Acceptance Record (DD250)."
PAGE 21
*
Add new Appendix A as included page 21.
4

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