The development of AR platforms continues unabated, with caliber enhancement far beyond the old 5.56mm and .308 Win. Included in these would be the Big Horn Armory AR500 in .500 Auto Max. Just such a gun shows this evolution very clearly.
The .500 Auto Max cartridge is a joint development by Greg Buchel, President of Big Horn Armory, and Tim Sundles of Buffalo Bore Ammunition. It is thus, in essence, a rimless case for the .500 S&W Magnum cartridge, meant to provide unparalleled stopping power in a semi-automatic platform. The .500 Auto Max can be reloaded using the same dies, shell holders, and load data as the .500 S&W except for a taper crimp since it headspaces off of the case mouth.
The foremost idea behind the .500 Auto Max is to achieve unparalleled stopping power at short to moderate ranges. With bullet weights from 350 through 440 grains at velocities of 1,900 to 2,300 fps, the trajectory is relatively flat out to 200 yards. This will make the cartridge extremely effective against heavily armored assailants or large game such as hogs, but also engine blocks. That the .500 Auto Max will easily blow through automotive body panels speaks to the power of this round.
Big Horn Armory’s AR500 is an AR-10 type receiver, modified to accept the .520-inch rim of the .500 Auto Max cartridge. The rifle includes an 18-inch, 1:24 twist stainless steel barrel, finished in nitride for improved surface hardness and resistance to corrosion. An adjustable gas block ensures trouble-free running with a wide range of loads, while the free-float M-LOK handguard and nickel-boron coated bolt carrier group add to the performance and ease of maintenance of this rifle.
With an ambidextrous selector and bolt catch, plus a superb trigger pulling at just 3-3.5 pounds, among its massive features, the AR500 design is one of the most interesting modified AR-15 size magazines—one stack to accommodate the .500 Auto Max cartridge for optimum reliability in feeding and performance.
Operational testing on the Echo Valley Training Center’s Jungle Walk Range proved the AR500 in diverse terrains and multiple-target scenarios. Performance against the range vehicles was nothing short of sterling—the .500 Auto Max cartridges used had no difficulty perforating the windshields and bodies of cars to engage the steel targets within. The muzzle brake truly tames recoil, holding the AR500 to a manageable level for even long shooting sessions.
As a pistol variant, it has the same reason for being manufactured: consumer demand. This year, due to more consumer demand, Big Horn Armory has released the AR500 pistol variant. The model comes with a 10-inch nitrided barrel featuring a 1:24 twist rate in an M-Lok-compatible handguard. An adjustable gas block was put in place to provide fine adjustment with sub-sonic loads and suppressors. The AR500 pistol weighs in at 8.1 pounds empty and is a compact yet very effective and potent firearm, as most users may need, but in a more compact package without losing its ballistic performance.
Big Horn Armory’s AR500 in rifle or pistol form is indeed a rather huge quantum leap in the capabilities brought by the AR platform. By tapping into the strength of the .500 Auto Max cartridge, the AR500 delivers versatility, power, and reliability that equip it for both big-game hunting and tactical operations with equal ease. An effective range of engagement out to 200 yards with a substantial terminal effect truly sets the AR500 apart in its class of semi-automatic rifles.