MK12 BarrelThese are Crane Spec. MK12 barrels. These barrels are the result of tens of thousands of dollars in development done by the U.S. government to give our Special Operations guys the best weapon system they can have. We have spoken with many riflemen who have used these barrels and carried them in combat and have found unanimous satisfaction with their reliability and accuracy. Specs:Material: 416R StainlessBarrel extension: M4 feed rampsChamber: optimized for use with MK262 (Black Hills 77gr equivalent)Twist: 1 in 7 right handContour: for use with OPS inc.Length: 18 in and threaded 1/2x28 for use with most common muzzle devicesWeight: 2 lbs 6.3 oz *****Centurion Arms barrels require no further break in********Requires gunsmith installation