Although the .280 Remington is considered to be a very balanced cartridge combining the best attributes of both cartridiges due to the high ballistic coefficient and sectional density, characteristic of 7mm calibers, it did not reach the popularity achieved by the .30-06 and .270 Win.
The famous wildcatter P.O Ackley, worked on the .280 Remington case in order to add it to the line of “Ackley Improved” cartridges and named it the .280 Ackley Improved 40 degrees. By 2008, Nosler standardized it and SAAMI accepted it. Ever since, the .280 Ackley Improved has earned great popularity in the US market. Several different companies manufacture rifles chambered in .280 AI, including the Ruger M77 Hawkeye, Savage 110, Browning X-Bolt and Weatherby Mark V.
The .280 AI is basically the .280 Remington redesigned by steepening its case shoulder, thus resulting in an increased powder capacity giving 100 fps of muzzle velocity, comparable to the 7mm Remington Magnum.
The differences between the .280 Remington and the .280 Ackley improved are minimal. A .280 Remington cartridge fired from a rifle chambered in .280 Ackley Improved will result in a case formed for the latter, which may be used for reloading.