Throw good money after bad?

[AKJC1977]

I think it would be a shot in the dark if your not real familiar with gun barrels,but sounds like you are to the point ya have not much to lose.There is some literature on crowns in the library,Don't know how in depth it gets. I dont know diddley bout the crown except it is a subtle chamfer that helps the pellet exit the barrel properly. Sure wouldnt know where to start whiddling. AKJC1977