BCM 16″ government profile, midlength gas system, button rifled barrel. Barrel is 1/7 twist, fully chrome lined with M4 feedramps. These have the factory BCM gas block, BCM barrel nut, and BCM flash hider factory installed; eliminating this guesswork. Ready for your BCM handguard of choice. Includes factory BCM gas tube and gas tube pin. Barrel nut wrench notches are mint condition.