Of all the calibres 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.
The .280 Ackley Improved casing is touted as launching a 7mm, 120 gr. bullet over 3,400 fps by Peterson. The .280 Ackley has a similar velocity to the 7mm Rem Mag, when using light to mid-weight bullets. It also tends to produce less recoil and less muzzle blast. When comparing the 280 Ackley with similar size cartridges, it has heavier bullet options than the 270 Win, and a flatter trajectory than the .30-06 Springfield.
Peterson’s .280 Ack Imp is designed for reloading. They have an ultrahard head and a thicker web which allows them to tolerate high pressure and allows more reloads per case.
Warning: Only use Peterson Cartridge Co. casings in firearms in good condition, designed, marked, and chambered for this cartridge. Do not use Peterson Cartridge Co casings for “fire forming” or any other purpose other than what they were designed and tested for. Peterson retains no responsibility for the enclosed casings if they are used outside of the manufacturer’s recommendations.