4150 QPQ coated inside and out for amazing corrosion resistance and durability. Carbine gas for longevity and reliability.Faxon Firearms barrels are the pinnacle of value. Manufactured 100% in-house from cradle-to-grave, these barrels are button-rifled and air-gauge tested to ensure superior accuracy. Barrel Material: 4150 CMV Steel Barrel Type: Button Rifled Barrel Caliber: 5.56 NATO Barrel Twist: 1:8 Barrel Length: 10.5 Barrel Profile: Light Barrel Gas System: Carbine Inside Finish: QPQ Nitride Outside Finish: QPQ Nitride Muzzle Thread: 1/2-28 TPI (Threads Per Inch) Gas Block Diameter: .750 Gas Block Journal Length: 1.1 Barrel Extension: M4 Weight: 1.10 lbs Magnetic Particle Inspected 11-degree Target Crown