Investigation of kinetic energy of .308 projectiles of different masses

Abstract

Projectile kinetic energy is a useful metric in ballistics that allows for the understanding of the magnitude of chemical potential energy that is transferred to projectiles in firearms. The purpose of this report is to investigate the effect that .308 projectile mass has on the kinetic energy of projectiles at muzzle exit of a .308 target rifle. Velocity was measured with the use of a radar chronograph, which was used to calculate the kinetic energy of the projectiles at that point in time. It was found that although velocity decreased as mass increased, kinetic energy increased as mass increased. The kinetic energy increased from approximately 3275J at 155 grains to 3962J at 220 grains. This was explained by the greater opportunity for work to be done on projectiles of greater mass due to slower volume expansion behind the projectile. This acts as a demonstration of Newton’s Second Law and variables that influence projectile behaviour in ballistics such as pressure evolution over time.