Firstly, the AR family has stretched its limits without making much noise over time. The AR-10 and AR-15 have set the baseline of the expectations of shooters from the platform in terms of the three main characteristics: rugged reliability, simple modularity, and straightforward serviceability. As the need for heavier work shifted, the manufacturers began wondering how far they could push the AR concept. Big Horn Armory’s response to it is the AR500: an AR-style rifle melted down around the gigantomachous .500 Auto Max cartridge.
.500 Auto Max was conceived as one of the simplest and boldest projects ever: take the already known power of the .500 Smith & Wesson Magnum and make it a rimless cartridge so that it can reliably cycle in a semi-automatic action. To make the concept a working cartridge that reloaded from roughly 275 to 700 grains, and where the factory powders are mostly used in the 350–600 grain window, Big Horn Armory has done so. The result allows an AR-pattern rifle to be equipped with devastating, hard-hitting potential without losing basic function.
However, the round doesn’t have to be one-note due to the power available. The spectrum of loads ranges from hardcast projectiles for deep penetration to hollow points for defense. Handloaders can use the available bullet types and velocities to create a variety of cartridges suitable for heavy hunting, pest control, and even unconventional tasks such as stopping a heavily laden vehicle. Essentially: .500 Auto Max is as adaptable as it is powerful.
More than a simple parts swap was required to allow a semi-auto AR to feed that cartridge. Incredibly, the AR500 shows some cheating on the part of the designers, as it still borrows the AR-10’s exterior dimensions, but changes the bolt face to accept the .520-inch rim, and the extractor/ejector systems are new to ensure reliable cycling. The barrels can be 10 or 18 inches and 1:24 twist with stainless steel standard and are treated for durability. Despite all that heavy-duty steel, most builds remain under 10 pounds—substantial, but still manageable in the field.
Ergonomics matter just as much. To achieve the necessary level of precision and reliability, Big Horn installed a free-floating M-LOK handguard, ambidextrous controls, and a crisp match-grade trigger of around 3.5 pounds on the AR500. Recoil is there, but a well-functioning muzzle brake softens it considerably—it’s more like a heavy 20-gauge than a shoulder-breaking cannon. Modified single-stack magazines, which are based on AR-15 geometry, are designed to work with big, straight-walled cartridges and are used for loading.
The ballistic performance is very impressive indeed. For example, a 440-grain bullet moving at approximately 1,650 feet per second will generate roughly 2,600 foot-pounds of energy—this is already well above the power of typical handgun cartridges. If the combinations are hotter and heavier, then the energy can get close to 4,000+ foot-pounds, thus the AR500 can be used for big-game hunting or anti-materiel activities.
Great accuracy has not been sacrificed for the sake of power. In the field, one can achieve with suitable optics the closest groups are about two inches at 100 yards, and the bullet’s trajectory remains practical up to around 150 yards. The 10-inch pistol-length configuration with a stabilizing brace makes the rifle compact enough for vehicle use or close-quarters tasks, thereby making the rifle attractive not only to hunters but also to some security and tactical users.
The aspect of practicality manifests itself in the operation. An adjustable gas block makes the rifle run smoothly with both supersonic and subsonic loads, and hence it is suppressor-friendly. This degree of customization broadens the rifle’s applications from being a tool for breaching and material works to a rugged survival rifle for remote regions.
When considering the larger picture, the AR500 is not an attempt to replace 5.56 NATO or .308 in general service. Instead, it is positioned in a very narrow niche where extreme terminal performance is required. This is yet another evolutionary branch of small arms development that widens the capabilities of AR-pattern firearms.
Big Horn Armory had progressed along with the plan and thus decided to relocate to a bigger facility in Cody, Wyoming, to quickly increase production, reduce waiting time, and hire more local people. The company has stated that the move has resulted in increased machining capacity, which is what makes meeting demand faster possible.
The AR500 is a statement, after all, that it is a known interface but with a lot more power underneath. Therefore, the AR500 is one of the most capable big-bore AR solutions available today for shooters who want massive stopping power but still in a familiar AR ergonomics package.