Big-bore ARs get full-production status with the
.450 Bushmaster Rifle and Carbine.

   I had just finished shooting groups and was measuring their sizes when a gray-haired regular of the local range came strolling over to assess the situation. Having arrived a few minutes earlier, he hadn't seen the gun I was testing. "Good shootin' muzzleloader," he said, eyeing the clusters of thumb-size holes in the target but ignoring the black rifle parked on the bench behind me. "Sure would be," I replied, "if it were a muzzleloader." ".45-70," he half asserted, half questioned before I had a chance to explain. "Nope, .450 Bushmaster," I said, nodding toward the AR. ".450 what? In an AR-15? I didn't know they made them that big." "Yeah, it's a real thumper," I answered with a smile. It's always good to get one over on the old guys.

   Big-bore ARs are not a new concept, though they are relatively obscure. For decades wildcatters and custom gunmakers have stuffed cartridges with bullets approaching the size of cocktail wieners into the platform, but even the most successful creations—the .458 SOCOM, .499 Leitner-Wise and .50 Beowulf being good examples—are at best semi-production affairs. It's not every day you come across rifles in these chamberings, not to mention factory-loaded ammunition for them.

The .450 Bushmaster cartridge is quite a bit fatter than the .223 Rem. and requires a widened ejection port. The feeding ramp on the .450 Bushmaster rifle is also enlarged to ensure reliable function.

   But now, thanks to a team effort by Bushmaster Firearms and Hornady, fans of the AR looking to take power to the next level have a factory-produced option in the .450 Bushmaster. A 20-in.-barreled rifle and a 16-in.-barreled carbine in the beefy cartridge are both rolling off Bushmaster's assembly lines, not to mention upper receivers, and factory-loaded ammo should be available in magazine-filling quantities from Hornady by the time you read this.

A Big-Bore Born
   The inspiration for the .450 Bushmaster is the .45 Professional, a wildcat cartridge formed by cutting a .284 Win. case off at the neck to accommodate a .45-caliber bullet. The .45 Professional is designed for short, .45 ACP-type bullets, but at the time of development, Hornady engineers wanted to employ the company's 250-grain, .452-in. SST Flex-Tip muzzleloader bullet (now called the FTX bullet) in the new cartridge. The velocities that the cartridge would be capable of producing mandated a larger, heavier bullet, and Hornady already had good results with inline muzzleloaders shooting the SST Flex-Tip at velocities of 2,000 fps and greater. So, in order to use the longer bullet and keep the cartridge overall length at 2.260 ins.—the same as the .223 Rem.—Hornady trimmed the case to 1.700 ins.

An Izzy-style muzzle brake helps tame the recoil of the .450 Bushmaster. It also promotes faster shot-to-shot recovery by reducing muzzle flip.



Born of the .284 Win., the .450 Bushmaster has a rim diameter of .473 in. It necessitates a larger bolt face but has more strength than a severely rebated rim.

The .450 Bushmaster is essentially a .284 Win. case cut off at the neck to accommodate a .452-inch bullet, then shortened to provide for a cartridge overall length of 2.260 ins.—the same as the .223 Rem.

   The resultant .450 Bushmaster case measures .499 in. at the case head and tapers slightly to .478 in. at the case mouth. Case capacity is 55.1 grains of water. Its rebated rim measures .473 in., the same as its .284 Win. parent and a deviation from most other big-bore AR cartridges that thin dramatically at the rim to keep the .447-in. diameter of the 7.62x39 mm. Remember, this is a joint effort with Bushmaster, so making bolts to fit a non-standard rim diameter is no big deal.

   Hornady says the .450 Bushmaster, with a maximum average operating pressure of 38,500 psi, will launch the 250-grain FTX bullet at 2,200 fps from a 20-in. barrel. In a 16-in. barrel, velocity drops only about 100 fps, according to the company, because the cartridge utilizes a propellant with a fast burn rate. I did not have a 16-in.-barreled carbine on hand to test this claim, but I chronographed the average muzzle velocity of 10 shots from a 20-inch barrel at 2,188 fps. The .450 Bushmaster is one cartridge that lives up to factory specs.

   Exiting the barrel at 2,188 fps, the 250-grain FTX load packs 2,659 ft.-lbs. of energy. That's more than twice the wallop of a 60-grain .223 Rem. Hornady TAP load. With a fully loaded, nine-round .450 Bushmaster magazine, that means you have almost 24,000 ft.-lbs of energy at your disposal, which is downright impressive firepower. The trajectory of the big bullet may not be as curvaceous as you think. Zeroed at 150 yds., the .450 Bushmaster is 1.41 ins. high at 100 yds., 4.08 ins. low at 200 yds. and 11.21 ins. low at 250 yds. continued on page 2

The .450 Bushmaster magazines utilize a specialized follower to keep the cartridges in a single stack. Capacity is drastically reduced by the rotund cartridges. A magazine that would normally hold 20 rounds of .223 Rem. only has room for five .450 Bushmaster cartridges.

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Sourcebox

Bushmaster Firearms
(800) 883-6229
www.bushmaster.com

Hornady
(800) 338-3220
www.hornady.com

Nightforce Optics
(208) 476-9814
www.nightforceoptics.com

In the Bush with the .450

Much has been made of hunting with black rifles in recent months—pro and con—and I come down unequivocally on the pro side. Freedom is about choice, not ignorance. I've used AR-15-style rifles for years on coyotes and varmints. For such applications, accurized ARs really are the better mousetrap.
   But when it comes to larger game, the most serious limitation of an otherwise excellent platform has been the power of the cartridge. Fortunately, in .223-length guns we've seen heavier hitters such as the .50 Beowulf and .458 SOCOM emerge, and now we have the .450 Bushmaster. Ballistically, the cartridge is essentially a hot .45-70 fired out of a semi-automatic platform with a detachable box magazine. With Hornady's production capacity behind it, you shouldn't have any trouble getting as much .450 Bushmaster ammunition as you want or can afford.
   I was fortunate enough to head to Troy Ayer's excellent Buck & Boar in Swansea, S.C. to try a pre-production .450 Bushmaster rifle and 250-grain Hornady FTX factory loads on wild boar hunt last spring. Ayer manages his wild boars to make them as purely European as possible, and he offers some of the most fun hog hunting I've experienced. On the trip, my group took 11 boars. When hit properly, each dropped dead in its tracks with no need for a follow-up shot—just as you'd expect with a 250-grain bullet leaving the muzzle at about 2,200 fps.
   My first was a medium-sized hog taken at a mere 10 yds. The bullet entered the chest cavity from a two-thirds-on angle, and the hog dropped on the spot. We recovered the bullet on the offside rear hindquarter after it penetrated about
22 ins. After impact, it had expanded to .695 inch and weighed 174.8 grains, retaining 70 percent of its unfired weight.
Am I believer? You bet. I've ordered a .450 Bushmaster upper and magazine as my new black bear gun. Now if we can only find a quiet factory- or user-installed safety, it really would be the better big-bore mousetrap.
—Mark A. Keefe IV
Editor in Chief, American Rifleman