The only polishing I've ever done besides by shooting a lot.
A friend sent me some Corbin's paste. Took all the tooling right out of it before it was ever fired.
Never had any copper fouling. But, the first 300 thru it were Moly'd.
It's a very slick shinning bore.
While sorting bullets with my load. It showed a marked preference for 40gr V max in .223's.
Less than .300".
Hope this helps, good luck,
George