Franklin Armory Pistol Length 7.5 inch 5.56 NATO Barrel Black 00-52503-BLK. 5 inch Pistol Barrel. 5.56 NATO. 1x9 Twist. 4140 Steel. Salt Bath Nitride Chamber Bore and Finish. Pistol Gas System. A4 Barrel Extension 8620 Steel. Index Pin Installed TDC....