Lots of people say that a polished barrel will throw the best pattern. I don't recall if it was the Nitro or hevi-shot site that says to clean your barrel between shots when patterning so you can see what the load can really do. On another board, the question was asked about cleaning between shots and most folks with great results run a bore snake or brush/patch between shots when patterning. I never paid attention to that before but I never had great patterns before either. I just picked up a 12 gauge bore snake to use when patterning