.450 Bushmaster

The .450 Bushmaster (derived from the .45 Professional) is a Rifle Cartridge/Firearm Concept, developed by Tim LeGendre of LeMAG FIREARMS LLC, and licensed to Bushmaster Firearms International for production and distribution. LeGendre still retains ownership of the concept. The .450 Bushmaster is built on the XM-15 platform and designed to be used in the standard M16 and AR-15 platforms, using modified magazines and upper receiver assemblies.

Bushmaster asked 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".  Bushmaster also requested a name change to ".450 Bushmaster", to which LeGendre agreed.

Based on the "Thumper" concept popularized by Jeff Cooper, the purpose of the cartridge was to provide guaranteed one-shot kills on big-game animals at 250 yards, using a large-bore (.44 cal or greater) cartridge in a semi-automatic rifle.

Col. Cooper was not a fan of the M16/AR-15 system due to its use of the .223 Remington/5.56x45mm NATO cartridges, however to Cooper's extreme delight, two 45 Professional/AR-15's were built and delivered to him, by LeGendre.

There are a number of Big Bore AR-15’s, on the market today. The Genesis of the 45 Professional concepts was years before the others were created, paving the way for copycatting. Today the 450 Bushmaster, in the hands of competent Hand-Loaders, uses ALL 45 caliber bullets. The .458 diameter line of bullet offerings, are being swagged, to the .452” standard, of the 450 Bushmaster's Bore, thus making hundreds of bullet choices available to the 450 Bushmaster Hand-Loader (see 450Bushmaster.net for process). The 450 Bushmaster is not a Low-Pressure pistol case, as can be found on the other Big Bore AR15's. The 450 Bushmaster is a Modern-day High Pressure Rifle Case, thus making better use of the efficiencies, of heavyset .458" bullets, delivering more speed and down range terminal performance, than can be had by the low pressure pistol cased cartridges, that are currently used in other AR-15's.

The .450 Bushmaster is available in a 16 inch or 20 barrel. It uses a standard 20 round AR-15 magazine, with a different follower to create a five-round .450 Bushmaster magazine. The followers can be purchased through Bushmaster. The XM-15 platform (similar to an AR-15) controls the recoil of this heavy round. The rifle recoil is more like a push than the hit a user would expect from a regular rifle. Hornady and Remington both now manufacture ammunition for the rifle.

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. This rifle has a free floating barrel making it extremely accurate—it is capable of sub 1 MOA.

It comes with an A3 “Flat-top” upper receiver with Picatinny rail for sight/optics mounting convenience, allowing for the choice of the sight or scope to mount on it.