.450 Bushmaster


The .450 Bushmaster is a rifle cartridge developed by Tim LeGendre of LeMag Firearms, and licensed to Bushmaster Firearms International. The.450 Bushmaster is designed to be used in the standard M16s and AR-15s, using modified magazines and upper receiver assemblies.

History

The.450 Bushmaster is descended from the "Thumper" concept popularized by gun writer Jeff Cooper. Cooper was dissatisfied with the small-diameter 5.56×45mm NATO of the AR-15, and envisioned a need for a large bore cartridge in a semi-automatic rifle to provide one-shot kills on big-game animals at 250 yards. Inspired by this, LeGendre developed his.45 Professional cartridge, and later built and delivered an AR-15 in.45 Professional to Cooper.
Bushmaster requested the ammunition manufacturer Hornady to produce the.45 Professional cartridge for this project, but Hornady wanted to shorten the cartridge case and overall length to accommodate their 0.452" 250-grain pointed SST Flex-Tip bullet. Bushmaster and LeGendre approved the change from a 1.772" case and 2.362" OAL to the now standard 1.700" case and 2.260" OAL. This permitted operation in the more abundant and popular AR-15 platform versus the AR-10 platform. Also, a name change to ".450 Bushmaster" was approved.

Loadings and ballistics

The.450 Bushmaster makes use of.452" bullets because of the lower impact velocities and energies would not adequately expand the heavier jacketed.458" bullets. The cartridge is chambered in bolt action rifles by Ruger, Savage, and Remington, Ruger's No. 1 single shot rifle, AR-15 rifles, as well as an AR-15 pistol by Franklin Armory.
Ballistically, the.450 Bushmaster has a rather flat trajectory out to 200 yards; if the firearm is zeroed at 150 yards, the user can expect to see a rise of 1.8 inches at 100 yards, zero at 150 yards, and a drop of 4.9 inches at 200 yards. The cartridge fits single-stacked in a standard AR-15 magazine with a single-stack follower. A 10-round AR-15 magazine body yields a four-round magazine, a 20-round AR-15 magazine body yields a five to seven-round magazine, and a 30-round body yields a nine-round magazine. Hornady, Remington and Federal now manufacture ammunition for the rifle, and Starline manufactures empty brass for handloading.