This is the barrel from our “SRC” rifle – similar to our 16″ M4 barrel, but it includes a 1913 military standard gas block (attached onto the barrel using taper pins) to which you can mount a variety of accessory front sights. The barrel material is 4150 Chrome Moly Vanadium 11595E steel, and it is chrome lined in Bore and Chamber for long wear and ease of cleaning. Button rifling is 1 turn in 9 inches – right hand twist for optimum accuracy with a wide range of .223 / 5.56mm ammunition. A Black Manganese Phosphate finished is applied for protection against rust and corrosion. This barrel includes the barrel extension (with M4 feed ramps), barrel nut, front handguard cap, 1913 mil std. gas block with sling swivel. It does not include a bayonet lug. The muzzle is threaded 1/2” x 28 T.P.I. to accept a variety of flash hiders or muzzle brakes.