I have a custom built 300 PRC built by Randy Melvin of Bull Mtn Rifles. Incredibly reputable gunsmith but has since retired. Last year the carbon ring was so bad it pulled bullets from the casing when ejected prior to firing. This year I’ve cleaned with thorough clean, butch’s, Montana extreme, and boretech eliminator along with other lower end products. The gun is built on a Borden LRX action with a lilja barrel. When functioning correctly it’s a dream but honestly I’m in a love hate relationship with the thing. I bought a repaint to confirm the issue. The barrel is spotless. After scrubbing and soaking for 6 days the carbon ring was mostly removed. 7 shots later it’s back in full force. Question now is should I have it reamed out a bit more for tolerance issues or keep scrubbing. It has never seen a factory load. All loads have been with either ADG or Peterson brass, H-1000 powder, either Winchester lrm or CCI magnums. Cases were trimmed to sammi specs. Please advise!