Proof Research PR15 Steel AR Barrel Features The Proof Research PR15 Steel AR Barrel is chambered in 6mm ARC and built from double stress-relieved 416R stainless steel the same base material Proof Research uses in its carbon fiber barrel line. This steel is a pre-hardened chromium stainless alloy developed in collaboration with rifle barrel makers specifically to meet the consistency and durability demands of precision shooting. Proof Research applies the identical drilling rifling and lapping process to this steel barrel as it does to its composite barrels meaning the same quality control and repeatability carries over despite the different material. A 1 in 7.5 inch twist rate is matched to the heavier bullet weights commonly loaded in 6mm ARC giving shooters the stabilization needed for long-range accuracy. At 20 inches long with a .750 inch gas journal diameter and a rifle length plus one gas system the barrel is configured for standard AR-15 pattern rifles rather than a compact pistol build. The 5/8x24 threaded muzzle is a common standard for 6mm and similar bore diameters giving builders easy access to a wide range of brakes compensators and suppressors. Finished in stainless steel the barrel offers strong corrosion resistance along with the distinct look that stainless construction provides. At 3 pounds 3 ounces this is a precision barrel for AR-15 builders focused on accuracy and it is available for sale at GrabAGun. Proof Research PR15 Steel AR Barrel Specifications Manufacturer: Proof Research Model: PR15 Steel AR Barrel Caliber: 6mm ARC Material: 416R Stainless Steel Color: Stainless Barrel Length: 20 Twist Rate: 1:7.5 Gas System Length: Rifle Length Gas Journal Diameter: .750 Thread Pattern: 5/8x24 Weight: 3 lbs 3 oz Compatible Hosts: AR-15 Available At: GrabAGun