I saw one of those carbines that were converted to 7.62x25. It had a bore that looked more like a sewer pipe. It was obvious that corrosive ammo had been used and then not cleaned properly.
It took a lot of work and time to get the piston nut freed up then get the piston out so all of the rust could be cleaned out. What a chore. Personally, I don't think it was worth the effort, the bore just didn't warrant it and because the only factory ammo available is corrosive, it means a complete takedown after every shooting session.
It did operate reliably though once everything was cleaned up, as much as it could be without replaceing parts anyway.
CanAm, why don't you pick up an inland or Iver Johnson replica or a grungy shot out US milsurp and rebarrel it? Probably be further ahead, unless your looking for a collectors piece. bearhunter