AR-STONER AR-15 pistol barrel chambered in 5.56x45mm NATO with a M4 contour and 1 in 7 twist. 10.5" overall length. Chrome moly steel with nitride finish. Barrels are drilled, reamed, and button rifled, profiled and chambered to SAAMI specifications. Compatible with surplus mil-spec ammunition or commercial 223 Remington. Designed for AR-15 pistol builds.