Use a rifled slug...the old style used in shotshell barrels.....smoothbores... I also recommend a cylinder choke.....My smoothbore cylinder gun shoots three shot groups at 25 yards into the size of a clay pigeon 10 out of 10 shots. Actual groups are about 2.5" at 25 yards.

I use iron sights and no scope. This rig is a 100 yard gun max.....but it's extremely powerful in that range.