If you are going to rust brown or rust blue a lock, it depends upon the finish you want, ie: scaled or polished...that determines how far to take the polish on a lock or barrel, for that matter. Some folks like the look of flat browning, that is, no shine. For that, drawfiling and 180 grit will suffice. But if you intend to card away all the scale, such as when you rust blue, then the higher the polish, the better the brown/blue will look, to my eye, anyway. I concur that original longrifles that I have examined are not taken to a high polish.