LeMAG FIREARMS LLC
Place of origin
Rebated rim, Straight wall
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.
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 (.223 Remington) of the AR-15, and envisioned a need for a large bore (.44 cal or greater) 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 to accommodate their 0.452" 250-grain pointed SST Flex-Tip bullet. Bushmaster and LeGendre approved the change from 1.771" to the now-standard 1.700", and a name change to ".450 Bushmaster".
Loadings and ballistics
The .450 Bushmaster is a high-pressure rifle case, thus making efficient use of heavy .452" bullets. The cartridge is chambered in bolt action rifles by Ruger, AR-15 rifles, as well as an AR-15 pistol by Franklin Armory.
Ballistically the round is very flat 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 2.4 inches at 200 yards. The cartridge fits single stacked in a standard AR-15 magazine with a single shot follower. A 10-round AR-15 magazine body will yield a 5-round magazine, a 20-round AR-15 magazine body will yield a 9-round magazine, and a 30-round body will yield a 13-round magazine. Hornady and Remington both now manufacture ammunition for the rifle.