Read on Rainier's website about the select medcon line. They have a proprietary surface hardening treatment they use on those barrels. I was going to either melonite or nitride mine so I called rainier and they said no because its already been done with Rainier's own system.

I talked to the guy for half an hour about it. Its Rainier's own type of melanite type or sort of treatment to surface harden the barrel and make it last a lot longer than either melanite or nitride when applied to stainless steel.