MIL-STD-662F
be found in ITOP 4-2-805. Spacing between triggering devices is a function of the expected velocity of the projectile being fired. In many instances, physical restriction, such as short overall distance from muzzle to test sample, dictates the spacing of the triggering devices. The last pair of triggering devices shall be placed at least 4 ft (122 cm) in front of test sample and should be protected from possible damage resulting from fragments.
5.2.2 Witness plate. The witness plate shall be 0.002 in. (0.05 mm) thick aluminum sheet for transparent armors and vision devices and 0.020 in. (0.51 mm) thick aluminum sheet for all other armors. The minimum size of the witness plate shall be 11 in. by l4 in. (279 mm X 356 mm) and be of sufficient size to be impacted by all fragments resulting from projectile penetration. The witness plate shall be made of 2024-T3, 2024-T4 or
5052 aluminum alloy sheet, and shall be located 6 + 0.5 in. (150 + 10 mm) behind and parallel to the armor test sample. When the test sample is a helmet the witness plate shall be rigidly mounted inside the helmet and 2 in. (51 mm) behind the area of impact and may be smaller than specified above so that it will fit inside the helmet. When the target presents a curved surface, such as a visor, the witness plate shall be located 6 +
0.5 in. (150 + 10 mm) behind the target, curved and oriented to maximize the probability of perpendicular impact.
5.3 Ballistic test procedure. The procedure listed below is a general description of the method for obtaining a V50BL(P). One should note that the actual method to be used may vary depending on target composition, specification or contract requirement.
5.3.1 Warm-up for constant velocity. When warmer rounds are needed for weapon or target alignment or establishment of a specific striking velocity, a test round shall be fired through the witness plate to determine the exact point of impact. Additional rounds shall be fired as required until the proper alignment and a stable striking velocity have been achieved. The propellant charge versus velocity curve for the weapon being used shall be referred to as a guide for establishing the required velocity within a practical + tolerance. Normally, this will be about + 25 ft/s (8 m/s).
5.3.2 Yaw. The test sample shall be mounted as described in 4.5. The point of impact shall be located on the test sample and shall be positioned to line up with the previously determined line of flight of the projectile. Yaw shall be measured for each round by yaw cards, flash radiograph or photography. Any round for which yaw is determined to be greater than 5o shall be disregarded in the calculation of the ballistic limit. In the case of a dispute concerning a particular barrel, yaw shall be measured by a photographic measurement system using a multi-flash light source to determine projectile velocity and yaw. Yaw shall be measured by the system to an accuracy of 0.5 degree.
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