The size of shrapnel balls in World War I was based on two considerations. One was the premise that a projectile energy of about was required to disable an enemy soldier. A typical World War I field gun shell at its maximum possible range traveling at a velocity of 250 feet/second, plus the additional velocity from the shrapnel bursting charge (about 150 feet per second), would give individual shrapnel bullets a velocity of 400 feet per second and an energy of 60 foot-pounds (81 joules): this was the minimum energy of a single half-inch lead-antimony ball of approximately , or 41-42 balls = 1 pound. Hence this was a typical field gun shrapnel bullet size.