When folks mention the AR platform, they tend to equate it with flexibility and consistent development—the AR-10 and AR-15 have become the workhorse for most shooters because they do so much so consistently. But then, occasionally a design puts that known formula into a fresh category: harder hits, alternative functions, more aggressive performance. Enter the Big Horn Armory AR500, an AR-style rifle built to handle the .500 Auto Max cartridge and bring big-bore power to a platform most of us already know how to use.
The .500 Auto Max began with a modest, ambitious concept: take the knockdown attitude of the .500 Smith & Wesson Magnum and modify it into a rimless cartridge that would cycle smoothly through a semi-automatic rifle. The result is a forcing platter of bullets—275- to 700-grain bullets, with factory loads typically ranging from around 350 to 600 grains. In short, it’s brute force teamed with semi-auto practicality.
That versatility is what makes the cartridge exciting. It isn’t just a “sledgehammer” cartridge—loaded properly, it can be used for game-stopping tasks with hardened projectiles, or customized for defensive applications with alternate bullet types. Handloaders and shooters willing to put in time at the reloading bench can optimize loads for hunting, remote bug control, or other demanding tasks where additional energy is crucial.
Designing a rifle that could withstand that energy necessitated fundamental changes. The AR500 takes the AR-10 footprint but recovers it: the bolt face is widened to receive the .520-inch rim, extractors and ejectors have been strengthened and reengineered, and the action has been smoothed out to function with the big cartridges dependably. Purchasers may have 10- or 18-inch stainless barrels, both finished for durability and fitted with a 1:24 twist. Notably, even with the bulk weight, most configurations weigh less than 10 pounds—easy for a rifle of this kind to push.
Ergonomics and comfort were not an afterthought. The AR500 features a free-floating M-LOK handguard, ambidextrous controls, and a crisp match-grade trigger set around 3.5 pounds. You do register the recoil, but a well-designed muzzle brake reduces much of the bite—more in the line of a stout 20-gauge rather than an unforgiving shoulder-breaker. The feeding is done by modified single-stack AR-15 magazines, a practical but effective solution to getting straight-walled, large-diameter rounds through smoothly.
Ballistically, the figures are impressive. A 440-grain bullet at about 1,650 feet per second generates over 2,600 foot-pounds of energy—more than most handgun rounds, and within the realm of the larger hunting cartridges. Hot-loaded, heavier projectiles can drive energy numbers still higher, placing the AR500 in the realm of truly large game or anti-material applications where penetration depth and momentum are important.
Accuracy is not neglected either. Fitted with the proper optic—a 1–8x variable, say—the field reports indicate solid, tight groups at 100 yards, with solid trajectories out to 150 yards in most loads. Switch to the 10-inch barrel with a brace, and the rifle is small enough for vehicle carry or close-quarters work, expanding its useful applications for some security or field-use applications.
The platform’s flexibility carries over into its gas system: an adjustable gas block cleans up cycling with supersonic and subsonic loads, and the rifle cooperates nicely with suppressors. That sort of dialing in opens doors—breaching, ranged anti-material duty, or survival tools in the boondocks—where a one-size-fits-all rifle would struggle.
Standing back, the AR500 is a rational progression, not a replacement for current cartridges such as 5.56 NATO or .308. It doesn’t attempt to be the go-to infantry round; it makes a place for itself where maximum effect and intuitive ergonomics are needed. Consider it another chapter in the long history of small arm progress—niche, but logical.
Big Horn Armory hasn’t been standing still, either. They moved to expand operations in Cody, Wyoming, to accelerate production, decrease wait times, and expand the regional workforce. That expansion facilitates quicker shipping and a more consistent supply for customers who need something different.
In the end, the AR500 is not a novelty. It shows what the AR design can accomplish when engineers reach beyond its boundaries: a practical, user-friendly big-bore rifle that provides actual stopping power without sacrificing modularity and ergonomics. For those shooters who desire a familiar platform but on the strong side of the power curve, the AR500 is an attractive option.