When folks refer to AR-style rifles, they often mean familiarity and versatility: the AR-10 and AR-15 lines have become standard-issue for militaries, police, and civilian shooters because they’re modular, low-maintenance, and easy to train on. But occasionally a niche dictates something much more radical—larger game, tougher tasks, or tasks that require raw stopping power. Big Horn Armory answered that call with the AR500, an AR specifically built with full-on big-bore capability on a platform most are already comfortable with due to the powerful .500 Auto Max cartridge.
The .500 Auto Max began as a bold idea: borrow the ballistics that others have come to admire in the .500 Smith & Wesson Magnum and restyle the cartridge as a rimless round that would be simply fed from a semi-automatic rifle. Big Horn Armory welcomed that challenge and developed a rimless, high-bore cartridge accepting bullets from roughly 275 to 700 grains, factory loads usually being in the 350 to 600 grain range. In short, it delivers magnum-class energy into a familiar, repeatable rifle package.
That brute strength doesn’t make the round simple. The .500 Auto Max is quietly versatile. Load it with hardcast bullets for man-eater stopping, choose expanding bullets for protection, or tweak handloads to an assignment—rural pest control by way of serious big-game hunting and even unusual jobs where stopping power is most important. Handloaders especially enjoy the cartridge’s variability; it’s easy to tailor performance to an application rather than accepting an all-around round.
Turning that cartridge into a viable rifle required more than simply replacing components. The AR500 is AR-10-style based but rebuilt where it counts: the bolt face has been expanded to accept the .520-inch rim, extractors and ejectors have been rearranged for reliable cycling, and receiver and buffer systems are strengthened. Barrel configurations are 10- or 18-inch stainless steel with a 1:24 twist and treatments for hardness. Even with the strengthened build, most models have the rifle under 10 pounds—heavy, but not unmanageable for a big-bore platform.
Comfort was not compromised, nor was ergonomics. The AR500 boasts a free-floating M-LOK handguard, ambidextrous controls, and a match-grade trigger that breaks positively at about 3.5 pounds. Recoil is present but damped by a large muzzle brake that keeps recoil nearer the feel of a stout shotgun than a runaway cannon fire. It is loaded from single-stack, altered AR-15-style magazines configured to the straight-walled cartridges, and the system cycles well when set up correctly.
Ballistically, the numbers are a draw-card. Standard performance would drive a 440-grain bullet at around 1,650 feet per second for some 2,600 foot-pounds of energy—some more than a .44 Magnum can deliver. Heavier, hotter loads drive that number still higher: some 350-grain overpressure loads have been clocked at over 2,300 feet per second and over 4,000 foot-pounds of energy. Those statistics place the AR500 into a category that can do nearly any large animal or tough stopping task.
Accuracy is not sacrificed for the punch. In field testing, a well-trained AR500 with quality glass will hold tight 2-inch groups at 100 yards, and the round flies flatter than most expect out to 150 yards. Short-barreled, pistol-configured setups with a 10-inch barrel and stabilizing brace make the rifle small enough for in-vehicle carry or close-quarters use, expanding its usefulness beyond open-country hunting into situations where mobility is an issue.
Practical adaptability is built into the platform: an adjustable gas block enables the rifle to cycle acceptably with both subsonic and supersonic bullets, and the gun becomes suppressor-friendly when it is tuned correctly. Those same capabilities make it usable in applications from breaching and light anti-material to a survival rifle for deep penetration forays, where one large rifle has to do many things.
Taking into account the thread of history, the AR500 is neither a move to replace mainstream calibers like .308 Winchester or 5.56 NATO; it’s a special adaptation of the AR concept for situations where pure impact is called for. It is part of a centuries-long tradition in small arms design where specialized needs call for design leaps of innovation—look at the change from smoothbore muskets to rifled barrels, or from bolt actions to semiauto designs. The AR500 simply challenges a new question to the AR platform and answers with ruthless efficiency.
Behind the rifle is Big Horn Armory, a company that has increased capacity and moved into a new, larger building in Cody, Wyoming, to keep up with demand and shorten delays. That growth has helped the company increase production, bring in new machines, and achieve more market presence—things owner Greg Buchel says are all about delivering capability consistently and affordably.
At its core, the AR500 is a statement and device: it shows the modular AR idea can be pushed to deliver unfettered kinetic energy without giving up the controls, ergonomics, and accessory matrix shooters love. For anyone who needs nearly unmatched stop power in a platform they already know, the AR500 and .500 Auto Max cartridge is a strong, though specialist, innovation in modern rifle design.