Big Horn Armory AR500 500 Auto Max AR-10 Semi-Auto Rifle, 18.5 in Barrel, Threaded with Brake, Free-Float M-LOK, 7+1
The Big Horn Armory AR500 is a large-frame AR chambered in 500 Auto Max, built on a DPMS-pattern receiver set and made in the USA. It features an 18.5-inch barrel with a 1:24 twist, a factory multi-port brake, and a free-float M-LOK handguard with a continuous top Picatinny rail. This rifle combines a robust 7075-T6 hard-anodized receiver set with practical enhancements like flip-up iron sights, a collapsible stock, and a slick-side upper with dust cover.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Overall Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: Minor scratches and blemishes are present on exterior surfaces. The firearm presents in great overall shape.
What's Included
- 1x 7-round modified SR-25-pattern steel magazine (500 Auto Max)
- Flip-up iron sights installed (Diamondhead front sight)
- Detachable bipod mounted on Picatinny rail adapter (installed)
- Picatinny riser rail installed on the upper receiver
Built on an AR-10 platform with a DPMS-pattern large-frame receiver set, the AR500 is purpose-built for the 500 Auto Max cartridge. It operates via a semi-automatic direct impingement system and is marked with Big Horn Armory's Cody, Wyoming origin.
The 18.5-inch barrel uses a 1:24 twist to stabilize heavy projectiles and is finished with a threaded muzzle, factory multi-port brake, and recessed crown. This setup delivers controlled muzzle behavior and secure accessory attachment at the muzzle.
The receivers are 7075-T6 aluminum with a hard-anodized finish, matched to stainless components treated in Hunter Black Nitride. The slick-side upper omits the forward assist while retaining a dust cover for debris protection. The overall finish is black for a uniform, durable appearance.
A free-float M-LOK handguard with a full-length top Picatinny rail provides mounting space along the entire upper line. Flip-up iron sights are installed, with a Diamondhead front sight confirmed. A Picatinny riser rail is fitted on the upper receiver, and a detachable bipod is mounted via a Picatinny adapter.
Furniture includes a collapsible carbine stock with a QD sling socket and a ventilated rubber buttpad, plus an overmolded textured AR-style pistol grip. The rifle uses modified SR-25 pattern magazines with a 7+1 capacity. Overall length is approximately 37–40.25 inches, length of pull about 11.5–15 inches, and weight around 9 lb.