I know this is a thread about longevity, but I'd like to add something I experienced firsthand with a chromed and then nitride barrel.
I had a S&W M&P15R, the 5.45x39 version. It originally came with a chrome lined barrel. I shot Wolf 60gr through it without issues. Decided to make it into a pistol so I bought another lower (to keep it legal going to a pistol) and cut down the chrome lined barrel to 11". Again no problems. Later I decided to make a training carbine out of it and bought a Ballistic Advantage melonited 14.5" barrel and extended FH for it. Then I started having failures-to-extract. A lot of FTE. Never remedied the problem and sold the upper and ammo to a guy with the admonition to liberally use a chamber brush while firing or it would FTE.
Now, to be fair it could've been an out-of-spec chamber. Could've been the steel-cased Wolf (there is no brass-cased 5.45 that I know of). Or it could've been the Melonite. Not sure. I have an MR556 pistol that I had the barrel nitrided on. Granted, I'm using brass-cased NATO ammo but I've never had a FTE from it so far.
I'm sure this muddies the water a bit but from my limited experience steel-cased ammo + nitriding doesn't do well.
11C2P '83-'87
Airborne Infantry
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