Hornady Superformance GMX Ammunition 308 Winchester 150 Grain GMX Boat Tail Lead-Free (20pk)SUPERFORMANCE ammunition is loaded with proprietary propellants that increase the velocity ratings up to 200 feet per second compared to other popular brands. Because there is no increase in pressure, regardless of the caliber, there is no increase in felt recoil but there IS an increase in efficiency and high speed performance. From sub zero arctic temperatures to almost unbearable desert heat, SUPERFORMANCE ammunition can withstand any hunting