as i was running my 17 hmr CZ American in, was cleaning it every five to fifty, was getting black residue on patch with rod, after fifty every 20
up to a 100 and now every 50 rounds i clean it with rod and patch. tried solvent on patch, but no copper residue, so now only clean dry patch, repeating until patch comes out clean.
and it shoot virtually zero at 100yds. rabbits clean kills cross hair on from 60 to 140. had about 300 rounds through it.