my 700 in 22-250 picks up copper like nothing ive ever seen. either because its still newer(less than 200rds down it) or just because its a 250...the copper laughs at regular solvent and a brush. i got some of the outters bore foam. let it sit a half hour...hit it with a few patches and most of the time its clean. occassionally, after shooting a bit, it will take 2 foam sessions. but thats after 20rds or so...i usually clean it every couple rounds..everyday after groundhog hunting usually..