Rockdoc,

You are right, I would have to explore a few options. Mike Orlen might be able to backbore the barrels and get rid of the pitting or just lenghten the cones. I don't think that lenghtening the cones alows for shooting longer shells. One does not lenghten the chamber but only the cones...
Did you notice an improvement in the pattern with the cone lenghtening?

jOe, does the pitting stop with the oiling of the gun?