Proof Research Barrel Features The Proof Research Barrel is machined from stainless steel with five grooves cut into an 18 inch rifle length profile designed to fit the AR-15 platform. A 1:7 inch twist rate stabilizes heavier .223 Wylde and 5.56 bullets at speed giving precision shooters and hunters consistent accuracy at extended distances. The standard barrel description keeps the contour balanced for both handling and heat management during strings of fire. A 5/8x24 threaded muzzle accepts standard AR-15 muzzle devices brakes and suppressors without requiring a gunsmith to re-thread the barrel. The .223 Wylde chamber splits the difference between .223 Remington and 5.56 NATO pressure and dimensions letting shooters run either cartridge through the same barrel with confidence. A .750 inch gas block diameter keeps the barrel compatible with the wide range of free float handguards and gas blocks already on the market. Stainless steel construction offers strong corrosion resistance and a long service life under repeated firing. For AR-15 owners looking to upgrade accuracy without a full custom build the Proof Research Barrel is available for sale at GrabAGun. Proof Research Barrel Specifications Manufacturer: Proof Research Model: Barrel Compatible Hosts: AR-15 Caliber: .223 Wylde Material: Stainless Steel Barrel Type: Rifle Length Twist Rate: 1:7 Diameter: .750 Grooves: 5 Thread Pattern: 5/8x24 Barrel Length: 18 Available At: GrabAGun