This 5.56 chambered 18 inch Performance Series Barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish. Our Performance Series barrels feature a Nickel Boron Coated Extended M4 Feed Ramp Extension.This barrel features a longer .750" profile dimension necessary for proper installation of the OPS Inc 12th model collar and... More