It's not uncommon to hear people claim a plain old carbon steel rimfire barrel will maintain reasonable accuracy for 100,000 rounds or more as long as its not ruined by over-zealous cleaning or pitted from neglect. It's not to hard for me to believe with the soft bullets and minimal powder charges used.

Nitrided 22 lr barrels are used in (at least) the CMMG and RTB conversion barrels, to the best of my knowledge the first wide-scale use of nitriding for rimfire barrels.

It will be interesting to see what kind of barrel life people report, given the surface hardness and corrosion resistance that is claimed for the treatment.

Andy