This problem is with a custom PacNor .458 barreled smokeless muzzle loader. Bullets
have to be sized to have no resistance at the muzzle in order to push them down to
the tighter breach end of the barrel. Even at that, carbon builds to the point the
barrel has to be cleaned after very few shots in order to again get the bullet to the
powder charge.

Suggestions?

I believe that SOMEHOW the breach end needs to be lapped in a way that does not
enlarge the bore diameter of the muzzle. What method could one go about to do that?

We should change our politicians
like we change dirty diapers....
and for the same reason.