BARREL LENGTH: 16 - CALIBER: 5.56 NATO - TWIST RATE: 1:8 - PROFILE/CONTOUR: M4 - MATERIAL: 4150 Chrome Moly Vanadium - FINISH: Parkerized - GAS SYS: Carbine - DIAMETER AT GAS PORT: .750 - MUZZLE THREAD: 1/2-28 - TREATMENT: Non RF85 - ADDITIONAL SPECS/NOTES: Barrel is compatible with .223 Ammunition.