Taylor's .62 Hawken, back in the 70's, had a bright area on the barrel from resting against the bench when loading - ie; worn browing, that appeared like a band when looking through the sights. Holding this bright 'band' level with the rear sight's flat, and putting the blade in the middle of the target, gave a perfect "0" for 325 yards, the distance to the 12" whitish coloured rock we used to shoot at in Squamish, BC. such a 'bright band on a browned smooth barrel would do the same - however, it is easier to sigth down the 'plain' of the barrel and place the blade on the taget, the ball striking on it's top edge. For longer ranges, merely hold up a bit of blade or sight base works. Bending the barrel is necessary for this sighting system to work on most RB smoothbores - except mine. Maybe somebody (the maker - Hunkeler) already bent the barrel - but it's perfect and worthwhile doing - correctly.