I second the lapping idea, I've lapped about all my guns after getting a kit for my revolver that I couldn't get the groups down enough. The kit I got was from LBT and was supposed to do a few guns, but I still have compound and have done most of my guns including my b/p ones. You are supposed to use bore size soft lead slugs and enough powder to push the bullet out of the barrel. I used maxi balls for my b/p job, you roll the bullets in the compound between glass or smooth metal plates and the compound gets imbedded in the soft lead. My original pistol went from a 3+" group to less than 1" at 50 yds ande all my other guns showed significant improvement and the b/p's are much easier to clean. I would shoot 10 rounds then clean and test fire a few rounds and if not satisfied I fired 10 more and on til satisfied.