This 5.56 chambered 7.5 inch Modern Series Barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish and QPQ coated M4 feed ramp extension.All NFA/ATF Rules ApplyYou may use this barrel with a lower receiver that is a Registered SBR, Machine Gun, or Pistol. Possession of this barrel along with a Non-NFA lower receiver is Prohibited, except when installed on a Pistol configuration firearm.Additional Info Length7.5Material4150 Chrome Moly VanadiumProfileDRPFinishQPQ Corrosion ResistantGas System LengthPistolGas Block Journal.750Twist Rate1:7 inchesMuzzle1/2x28 ThreadedWeight17ozOther InfoNo