Hey guys, don't jump in ahead of me with your answers! Read the name of the forum and keep aware that the questions are asked to Veral Smith, not anybody. I'm very strict on enforcing this, with the delete button, if I see error in an answer.
However I'm leaving the post by Mobada in place, because it's half right but completely wrong.
All revolvers have varying dimensions between throats and barrel and all can be fire lapped. Just open up the cylinder throats till they are a bit larger than the barrel, then firelap.
As for the pitted barrel, firelap it then follow the very detailed lap instructions on how to fix the pits so they don't hinder performance.
You can use the round balls to firelap, by putting a little compound on the noses and smearing some in the bore with a bore brush. Compound on the nose will slide back around the ball when you touch her off. Keep the charges low as possible to avoid leading. If a cap and ball revolver needs to have the cylinder throats opened up, purchase a reamer that is at least .001 larger than barrel groove diameter and ream all the way to the botton of the chambers, to clean up any rust, buildup, etc but also to enlarge them a bit for a tad more powder room. The guns I've played with have tapered chambers and a reamer fixes it.
Most machine tool supply houses, probably all, will speical order custom diamete chucking reamers, and manufacures make many sizes in .001 increments. They aren't expensive, like having a custom shop which caters to gun builders do the grinding.