450 Bushmaster: Extraordinary Large Bore Cartridge

There is a long-standing debate among avid shooters concerning the effectiveness of small diameter, lightweight, fast-moving bullets versus large diameter, heavyweight, slow-moving bullets

450 Bushmaster: Extraordinary Large Bore Cartridge

There is a long-standing debate among avid shooters concerning the effectiveness of small diameter, lightweight, fast-moving bullets versus large diameter, heavyweight, slow-moving bullets, and this debate is especially germane to military personnel. Consequently, ever since the introduction of the 5.56 x 45mm NATO cartridge during the Vietnam War era, military personnel have complained about its relative lack of stopping power; especially among special forces operators. Thus, many new rifle cartridges with significantly larger bullets have been developed in the intervening years that are specifically designed to fit and cycle in the AR-15/M16 platform.

However, the .450 Bushmaster which was originally conceived by Colonel Jeff Cooper and developed by Tim LeGendre of LeMag Firearms and then licensed to Bushmaster Firearms International is designed to be used in standard  AR-15 and M16 rifles with modified upper receiver assemblies and magazines and thus, it represents the extreme end of the large diameter, heavy bullet, spectrum. But, unlike many of its cousins, it is definitely not a slow cartridge!


In fact, the original concept for this cartridge was developed by popular gun writer Colonel Jeff Cooper who was an avid proponent of the .45 ACP cartridge over the 9mm Parabellum and who, like so many avid shooters, was dissatisfied with the small-diameter, lightweight, .22 caliber bullet used in the 5.56 x 45mm NATO cartridge (aka .223 Remington). Therefore, Cooper envisioned a large-bore cartridge of at least .44 caliber for use in a semi-automatic rifle that was capable of providing one-shot kills on both enemy personnel and medium to large game animals out to 250 yards.

So, inspired by Jeff Cooper’s original cartridge concept which he called the “Thumper”, Tim LeGendre of LeMag Firearms used the .284 Winchester as a parent case to develop a straight-walled rifle cartridge with a rebated rim that he called the .45 Professional cartridge and, he later built and delivered an AR-15 chambered for his new cartridge to Colonel Cooper. Then, Bushmaster approached ammunition manufacturer Hornady to produce a small quantity of the new .45 Professional cartridge for testing but, Hornady wanted to shorten the cartridge case slightly from 1.771″ to the now-standard 1.700″ in order to accommodate their 0.452 inch, 250-grain, pointed SST Flex-Tip bullet and both LeGendre and Bushmaster approved the change. Thus, the name of the new cartridge was subsequently changed to “.450 Bushmaster”.

450 Bushmaster  vs. 45 ACP  vs. 9mm


Concerning its ballistics, the .450 Bushmaster is a high-pressure round with a maximum pressure of 40,000 psi as established by the Small Arms and Ammunition Manufacturers Institute (SAAMI) and is capable of firing a .45 caliber, 250 grain, bullet at over 2,200 fps and a 260-grain bullet at over 2,100 fps. In addition, this round has a surprisingly flat trajectory for such a heavy bullet with such a large diameter and thus, if the firearm is zeroed at 150 yards, a shooter can expect to see a rise of only 1.8 inches at 100 yards and a drop of only 2.4 inches at 200 yards. Plus, with a whopping 2,800 foot-pounds of kinetic energy at the muzzle, it has plenty of knockdown power to stop everything from feral hogs to elk and moose and even bears within its designated target range of 250 yards.

Magazine Compatibility

Both Hornady and Remington now commercially manufacture .450 Bushmaster ammunition and, because this cartridge was specifically designed with the AR-15 platform in mind, it easily fits single stacked in a standard AR-15 magazine with a single shot follower. Therefore, a 10-round AR-15 magazine body will contain 5 rounds and a 20-round AR-15 magazine body will contain 9-rounds whereas, a 30-round magazine body will contain 13 rounds.


Consequently, even though magazine capacity is limited, there is considerable interest in this relatively new semiautomatic rifle cartridge among military personnel since it provides special forces operators the instantaneous, one-shot, stopping power that is lacking with the 5.56 x 45mm NATO cartridge which can very well mean the difference between life and death in certain Close Quarters Battle situations.

In addition, it has also become a popular round among avid hunters of both medium and large game species since it provides a relatively flat trajectory out to 250 yards when longer shots are called for and, it also makes the perfect choice for hunters who commonly hunt dangerous game in thick brush due to its extreme kinetic energy and deep penetration. Thus, many hunters who prefer the AR-15 platform consider it to be the ultimate “brush gun” cartridge as well as the perfect dangerous game cartridge. Thus, due to its growing popularity, several firearms manufacturers such as Ruger now offer bolt action rifles chambered for this cartridge as well.

(photo credit Sturm, Ruger & Co., Inc.)

Parting Thoughts

So, with a muzzle velocity of 2,100 fps to 2,200 fps, the .450 Bushmaster is certainly not a slow cartridge and, with a 250 grain or 260-grain bullet delivering 2,800 ft/lbs of kinetic energy at the muzzle, it is absolutely devastating on impact! Therefore, it is no wonder that this cartridge has become so popular among military Special Forces personnel as well as medium and large game hunters who prefer the AR-15 platform since it has the power needed to instantly stop enemy soldiers wearing standard body armor as well as both large and dangerous game species at relatively long ranges.

The .450 Bushmaster cartridge is very likely to continue to grow in popularity as more firearms manufacturers produce rifles chambered for this round and more ammunition manufacturers produce ammunition with a wider range of bullet weights and designs. So, if you are a hunter who has a preference for the AR-15 platform and/or who commonly hunts medium to large game species and, especially dangerous game species such as Feral Hogs or Brown Bear in thick brush, then you should definitely consider adding a rifle chambered for the .450 Bushmaster to your arsenal since it certainly fits the bill!

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