Butch's Bore Shine. I have been a high power competitor for 40+ years. Hoppes #9 used to be the only choice but, products evolved. Butch's Bore Shine gives me the best results. I use J&B Bore Paste to remove copper fowling after 500 to 1000 rounds.
A heavily soaked patch is used to coat the bore several times and the rifle is placed muzzle down to allow the solution to dun down the full length of the bore. More is applied as needed until the patches come out clean. Rem Oil is used to coat the bore for storage, until the next match.