I own a Ruger AR-556 AR-15. Ruger states that it uses a Cold Hammer-Forged 4140 chrome-moly steel barrel with a matte black oxide finish. They do not specify what the said barrel rifling is lined with. I have called them on several occasions and received different answers on this Q?. Such as, Nitride lined, Melonite lined, and, being it is CHF 4140 chrome-moly barrel, it's chrome lined from the material of the barrel. Is there ANYONE that can tell me the TRUTH about how the said barrel rifling IS lined, if any? And, whatever answer you give me, should I look for another barrel if it ISN'T any of the above given answers?