The .450 Bushmaster is a powerful rifle cartridge designed for big-game hunting, specifically for use in AR-15-style rifles. It was developed by Tim LeGendre of LeMag Firearms and later adopted by Bushmaster Firearms International.

The .450 Bushmaster cartridge has a bullet diameter of .452 inches (11.5mm) and utilizes a straight-walled brass case with a rebated rim. It was created as a short-range, large-bore cartridge for hunting medium to large game, particularly in areas with straight-walled cartridge restrictions.

One of the primary motivations behind the development of the .450 Bushmaster was to provide a cartridge that could be chambered in the popular AR-15 platform while delivering significant stopping power. It was specifically designed to be compatible with standard AR-15 magazines and components, allowing for easy conversion of existing rifles.

The .450 Bushmaster is known for its excellent terminal performance, delivering high energy and stopping power on game animals within short to medium ranges. It has gained popularity among hunters for its ability to take down large-bodied game such as deer, feral hogs, and black bear.

Due to its power and recoil, the .450 Bushmaster is not typically used for long-range shooting. Its effective range is generally limited to a few hundred yards, making it well-suited for hunting in dense woods or other close-quarters environments.

In addition to hunting applications, the .450 Bushmaster has also found use in some law enforcement and military roles, particularly for close-quarters situations where a larger caliber and stopping power are desired.

Overall, the .450 Bushmaster offers a potent option for hunters and shooters who desire a big-bore cartridge in the familiar AR-15 platform, combining the versatility of the rifle with the power needed for taking down large game at shorter ranges.