The Effect of an Unconditioned Barrel on Temperature Conditioned 5.56mm Cartridges

Report No. ARL-TR-4748
Authors: Robert P. Kaste
Date/Pages: June 2009; 26 pages
Abstract: Several organizations independently tested the same lot of 5.56mm ammunition temperature conditioned to -55, 125, and 160 ¿F and reported discrepancies in chamber pressures and muzzle velocities. These discrepancies precipitated this investigation into the time required to temperature condition 5.56mm ammunition and the effect of using an unconditioned weapon to fire conditioned ammunition. The unconditioned weapon dramatically affected the temperature of the conditioned ammunition. Substantial changes in the cartridge temperature occurred when the cartridge remained in the chamber, even for a short time. Cartridges loaded into a 30 round magazine took about 3 times as long to change temperature as did single rounds.
Distribution: Approved for public release
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Last Update / Reviewed: June 1, 2009