Well, it's time to go back to resurrecting an abused rifle.
What abrasives have you tried for fire lapping with paper patches?
Grinding compounds smeared on the patches before firing?
Dry powders rubbed on the patch?
Dry powders sprinkled on a fixative coating?
What kind of results have you achieved?
How much larger was the bore next to the chamber versus at the muzzle?
Can you determine how much metal removal was achieved for how many shots fired?