Hornady Superformance, 300 Winchester Magnum, 165 Grain, CX, 20 Round Box 820264 Increase your rifle's performance up to 200 fps without extra chamber pressure, recoil, muzzle blast, temperature sensitivity, fouling, or loss of accuracy. Superformance uses progressive propellants that take your favorite bullets to levels of performance that are simply unattainable with conventional ammunition.