I have a 3200 Remington that's about 35 years old now. I haven't kept track and I won't say it has been shot a lot, but it has been shot steadily over the years. The inside of the barrels have a black finish which I have to presume is just a very thorough blue job. There's not the first sign of that finish wearing through to bright steel. How is that? My take is that shotgun barrels don't wear much, chokes either.