Later the rotation was effected by a cupped copper disc called an "automatic gas-check" attached to the base end of the projectile. The powder gas pressure expanded the rim of the gas check into the rifling grooves and prevented the escape of gas; it also firmly fixed the gas check to the projectile, thus causing it to rotate. A more regular and efficient action of the powder gas was thus ensured, with a corresponding greater range and an improvement in accuracy.
Later the rotation was effected by a cupped copper disc called an "automatic gas-check" attached to the base end of the projectile The powder gas pressure expanded the rim of the gas check into the rif.ling grooves and prevented the escape of gas; it also firmly fixed the ga,s check to the projectile thus causing it to rotate A more regular and efficient action of the powder gas was thus ensured, with a corresponding greater range and an improvement in accuracy.