Abstract: The terminal effectiveness of fin stabilized, subcaliber armor piercing projectiles depends primarily on the impact velocity at the target. The aerodynamic drag and related velocity decay experienced over the trajectory from the gun to target is reduced by shortening the length of the acceleration transfer interface between subcaliber projectile and discarding sabot. This applies for multiple annular grooves and helical grooves. Special groove configurations to reduce the pressure drag and related boundary layer shock wave interaction are disclosed. The reduction in length of the acceleration transmitting interface permits its location to a position aft of the point of boundary layer transition from laminar to turbulent flow and therewith to take advantage of the low frictional coefficient of the laminar boundary layer over a large portion of the subcaliber projectile. The resulting reduction in aerodynamic drag is particularly effective for mid caliber projectiles.

Abstract: The invention concerns a fin-stabilized discarding sabot projectile for employment from a rifled barrel and is particularly suitable for automatic cannons having calibers from 12.7 to 70 millimeters. The full rate of spin commensurate with the rifling twist of a specific barrel and the muzzle velocity is imparted to the projectile during launch using a rotating band which is fixed and an integral component of the discarding sabot. The discarding sabot design involves the in-place injection molding of the sabot body, including a seal with obturator, onto the fin-stabilized projectile. The absence of slipping rotating band provides for a rugged sabot configuration which is particularly important for ammunition employed from automatic cannons. Launching at full rate of spin results in large centrifugal forces acting on the components of the sabot which provides for instantaneous and precise sabot separation upon projectile exit from the muzzle.

Abstract: The invention concerns a fin-stabilized projectile for employment from a rifled barrel and is particularly suitable for automatic cannons having calibers from 12.7 to 70 millimeters. The full rate of spin commensurate with the rifling twist of a specific barrel and the muzzle velocity is imparted to the projectile during launch using a rotating band which is fixed and an integral component of the discarding sabot. Subsequent to exit from the muzzle of the gun the rate of spin of the projectile is decelerated rapidly by aerodynamic damping to avoid potential adverse effects due to Magnus moments. The aerodynamic design of the fins is such that the projectile spin reaches a steady state rate of spin which is at least 50 percent larger than the nutation frequency of the projectile. By means of this spin tuning resonance instability and roll lock-in are avoided over the operational range of the projectile.