Dan is right on with his advice. I had the same problem with a newly aquired TC hawken. After cleaning with 0000 steel wool and PB blaster and polishing the bore with JB paste, it looked terrific. After a couple of range sessions, accuaracy fell off and loading became difficult. I cleaned and polished the bore again. Accuracy was again good but loading was still problematic after 6 or 7 shots even with swabbing the bore. I polished for a third time and looked at the bore with it lighted from the breech. I was amazed to find microscopic pits full length that did not show when inspecting from the muzzle. The difficult loading was from a three inch length of bore with bad pitting, also not visible when looked at from the muzzle. I sent the barrel to Bob Hoyt for reboring and rifling to 54 cal.