MIL-STD-662F
5.3.3 First firing. For acceptance testing, the first round shall be loaded with a reference propellant charge so that the striking velocity is approximately 75 to l00 ft/s (23 to 30 m/s) above the minimum required V50BL(P) as given by the appropriate specification. For most other types of ballistic tests, the first round shall be loaded with a reference propellant charge where the estimated likelihood of either complete or partial penetration is 50%.
5.3.4 Examination of witness plate. The witness plate shall be examined for penetration by holding it up to a light to observe light passage. A complete penetration is recorded when any light passes through the witness plate. If no light is visible through the witness plate, a partial penetration is recorded.
5.3.5 Subsequent firings. If the first round fired yields a complete penetration, the propellant charge for the second round shall be equal to that of the first round minus a propellant decrement for a 50 or 100 ft/s (15 or 30 m/s) velocity decrease in order to obtain a partial penetration. If the first round fired yields a partial penetration, the propellant charge for the second round shall be equal to that of the first round plus a propellant increment for a 50 ft/s (15 m/s) velocity increase in order to obtain a complete penetration. A propellant increment or decrement, as applicable, for at least 50 ft/s (15 m/s) shall be used until one partial and one complete penetration is obtained. After obtaining a partial and a complete penetration, the propellant increment or decrement for
50 ft/s (15 m/s) shall be used. Firing shall be continued until a V50BL(P) is determined, using a random pattern of impact sites, unless otherwise specified.
5.4 Calculation of the V50 BL(P) ballistic limit. The V50 BL(P) shall be calculated by taking the arithmetic mean of an equal number of the highest partial and the lowest complete penetration impact velocities within the allowable velocity span as defined by the contracting officer (see USATECOM TOP 2-2-7l0).
5.5 Computation of striking velocity. Instrumentation velocities shall be corrected as follows:
VS = VI - VL
Where:
VS = Striking velocity at the test sample
VI = Instrumentation velocity
= Distance (between sensory devices) Time (chronograph reading)
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