Not cheap but Remington copper sabot slugs (there are several versions) are extremely accurate out of a rifled barrel with a scope. Copper solids will group at 3 to 5 inches at 100 yards. I've taken deer at well over 100 yards with my 870 SP, rifled barrel, Leupold scope, and Rem. copper solid slugs. (I would, of course, prefer a rifle - a firearm limited to poachers in Iowa.)
