Spit-Hole Effects on the Ballistics of a 7.62-mm Cartridge

The U.S. Army Research Laboratory conducted a study to examine the effects of a small caliber (7.62-mm) cartridge s spit-hole on the interior ballistic performance of the cartridge. The performance metrics evaluated were cartridge pressure and muzzle velocity. The laboratory incorporated its custom breech apparatus that measures primer pocket pressure, and used standard midcase pressure measurements and high-speed imaging to evaluate early projectile motion out of a custom-built short barrel gun.