.280 Remington Ackley Improved (using Sierra bullets)
Date: Mar 31 2021
The .280 Remington Ackley Improved can be traced back to wildcat cartridges developed around World War II, such as the .285 O.K.H., 7mm-06 Mashburn and 7mm-06. Each of these are variations of the .30-06 case necked to 7mm. Remington Recognized the value of this cartridge and in 1957 offered .280 Remington rifles and ammunition. It was based on the .30-03 case and is around .046 inch longer than the .30-06 case. It is a great cartridge with many applications that include long-range competition and big-game hunting. Unfortunately, industry maximum average pressure limits were comparatively low, which left performance on the table.
Experimenters soon began blowing out the .280 Remington case to increase powder capacity and performance, with the Ackley version (by Parker 0. Ackley) becoming popular. In 2006 Nosler introduced it to SAAMI, and it became an industry standardized cartridge. With the shoulder blown out to a 40-degree angle to increase capacity, and pressures increased, it launches popular 140- to 160-grain bullets at nearly the same velocities as the 7mm Remington Magnum. It offers this performance in a standard (non-belted) case while utilizing less powder, producing less throat erosion lower and recoil. In testing here, extreme spreads were found to be remarkably low, and accuracy was very good.
Nosler lists factory ammunition with various 140-grain bullets at 3,150 fps, with the 150-grain versions advertised at 2,900 and 2,930 fps. The 160-grain Partition is listed at 2,950 fps.
The .280 Remington Ackley Improved thrives on powder with a burn rate similar to Hodgdon H-4831SC, With Hodgdon H-1000, IMR-7828, VihtaVuori N-165, Ramshot Magnum, Accurate MagPro, Alliant Reloder 19 and Reloder 22 each producing good results. When using spherical (or Ball) powders, do not reduce the starting loads, as hang-fires and erratic ignition can occur. A standard large rifle primer will offer proper powder ignition, with Winchester Large Rifle primers being used to develop the accompanying data.
Rifles that were built prior to the .280 Remington Ackley Improved becoming an industry standardized cartridge may have different chamber dimensions. As such, special caution should be taken when developing handloads or using the accompanying data.