Reloading The .450 Bushmaster
THE .450 Bushmaster was introduced in 2007 to provide a more powerful cartridge that would increase the performance of AR-15 rifles. Shooting a .452 calibre 250gn bullet at 2200 fps it did indeed boost striking energies considerably compared with the 5.56 NATO’s small, light 55gn bullet leaving the muzzle at 3300fps. Like the 6.5mm Creedmoor, the .450BM got off to a slow start and took a while to gain popularity; I can hardly believe it was 12 years before I got a rifle to review, let alone reload!
The .450 Bushmaster is a cartridge that’s little more complicated to reload than the average bottleneck centrefire. I've heard it described as being a shortened .284 Winchester necked up to shoot .45 calibre bullets; a sawn-off .45-70 and a lengthened .45 ACP. Not one of these descriptions really does the cartridge justice.
It is a straight case measuring 1.70" tapering from 0.500" at the head to 0.48" at the mouth. The rebated rim measures 0.473 which is standard for rimless cartridges in the .30-06 class. The case is designed
