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|Place of origin||United States|
|Designer||LeMAG FIREARMS LLC|
|Parent case||.284 Winchester|
|Case type||Rebated rim, Straight wall|
|Bullet diameter||.452 in (11.5 mm)|
|Neck diameter||.473 in (12.0 mm)|
|Case length||1.700 in (43.2 mm)|
|Maximum pressure (SAAMI)||40,000 psi (280 MPa)|
|Test barrel length: 20 in (508 mm)
Source(s): Hornady & Remington
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 M16 and AR-15 platforms, 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,[when?] and later[when?] built and delivered an AR-15 in .45 Professional to Cooper.
Bushmaster requested[when?] 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
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.
- PREMIER® ACCUTIP™ 450 BUSHMASTER Remington Arms Company
- Frank C. Barnes (5 October 2012). Cartridges of the World: A Complete Illustrated Reference for More Than 1,500 Cartridges. Gun Digest Books. pp. 97–. ISBN 1-4402-3059-5.
- "45 Cal .452 250 gr FTX® (450 Bushmaster)". Hornady. Retrieved 2016-08-13.
- Pridgen, D.K. "FRANKLIN ARMORY XO-26 .450 BUSHMASTER". Tactical-Life Magazine. Retrieved 26 Feb 2014.
- Hornady Manufacturing - 450 Bushmaster (Archived 2009-08-05)
- Bushmaster .450 Rifle & Carbine - Bushmaster Firearms (Archived 2009-08-05)