Some people refer to it as the .280 Improved. Other people call it the .280 Ackley. On casings made by Peterson, they are headstamped .280 Ack Imp. Whichever way you refer to it, the concept popularized by gunsmith and wildcatter P.O. Ackley, is here to stay. Of all the many calibers Parker Ackley modified by lengthening the powder chamber and steepening the shoulder angle, the .280 Ackley is the only one, so far, that has been adopted by SAAMI. And it is a high performer. Mfg: Peterson Cartridge