the 280 AI set out to improve the .280 Rem by steeping the shoulder to 40 degrees to increase powder capacity. Weatherby is known for ballistics and velocity. Caliber 280 Ackley Improved Bullet Type Hammer Custom Bullet Weight 139 gr Muzzle Energy 2871 ft lbs Boxes Per Case 10 Rounds Per Box 20 Muzzle Velocity 3050 fps Unit Of Measure box