When it comes to getting more power out of the AR-15 platform, shooters have been limited for years. The need for more power out of a semi-automatic rifle was recognized long ago, but it is only in the last decade or two that manufacturers have stepped up to offer more options. The two primary big-bore AR-15 cartridges on the market today are the .50 Beowulf and the .458 SOCOM. But there’s another option out there: the .450 Bushmaster.
While the Beowulf and the SOCOM were originally designed to provide military and police forces with a larger-caliber harder-hitting cartridge in the AR-15 platform, the .450 Bushmaster was designed with hunting in mind. Inspired by legendary shooter and gun writer Jeff Cooper, the .450 Bushmaster was designed by Tim LeGendre, licensed to Bushmaster, and ammunition was created by Hornady.
Unlike the .458 SOCOM, which uses .458”-diameter rifle bullets, the .450 Bushmaster was designed around .452”-diameter pistol bullets, due to the fact that the .45-caliber rifle bullets are designed for use in magnum cartridges such as the .458 Winchester Magnum, and may not provide adequate hunting performance in the smaller .450 Bushmaster. Because of that, the .450 Bushmaster uses the same bullets as the .45 Colt, .454 Casull, or .460 S&W.
The .450 Bushmaster case is based off the .284 Winchester, featuring a .500”-diameter base and a .473”-diameter rim. That .308 Winchester-sized rim in the AR-15 means that pressures have to be kept low, with a maximum pressure of 38,500 psi. Despite that, the .450 Bushmaster is capable of impressive performance.
The .450 Bushmaster can push a 225-grain bullet to nearly 2,500 feet per second, and a 300-grain bullet to nearly 2,000 feet per second, for muzzle energies between 2,600 and 3,100 foot-pounds. Heavier bullets can be loaded too, but handloaders will have to pay attention to overall length and ability to feed through an AR-15 magazine. Because of the .450 Bushmaster’s size, magazine capacity in standard AR-15 magazines is limited. Expect to fit 4 rounds in a 10-round magazine, 6 to 7 rounds in a 20-round magazine, and 9 rounds in a 30-round magazine.
As with many other less common cartridges, the real knock on the .450 Bushmaster is its ammunition cost. Today during the great ammo crisis of 2020, the cheapest ammunition available is about $1.70 a round. Handloading is the name of the game if you want to be able to shoot the .450 Bushmaster cheaply.
Does the .450 Bushmaster bring anything to the table that the .458 SOCOM and .50 Beowulf don’t? Probably not, and factory support for the .450 Bushmaster could be questionable in the future, now that parent company Remington has gone bankrupt and the Bushmaster brand has been sold to Franklin Armory. If you have a .450 Bushmaster already, it’s probably time to stock up on ammunition and components. The .450 Bushmaster will definitely stand you in good stead in your survival armory, but if you’re starting from scratch looking for a big-bore AR-15, you may want to stick to the tried and true .50 Beowulf and .458 SOCOM.