I have done a bit of shotgun magic. Until the last two years Indiana was a shotgun only state so to speak. The barrel pinning goes a long way to get them shooting consistantly. We used to buy the browning a-bolt shotgun and the H/R ultra-slug hunters quite a bit and do some great groupings with them also.
It is not as easy as it would appear and a good Dr. sluggun would have saved us quite a bit of time and money. I can still remember trying to get a double to shoot to the same point of impact with a dual back sight and single front sight.