Speaking of averages, IMO a rifled barrel with the right loads will usually outshoot a smoothie. BUT I have seen some smoothbores that would amaze you! The old Ithaca 20" smoothbore Deerslayer I used to own would put three of a certain lot of Remington Foster-type slugs into 3" at 100 yards. A friend's Remington 870 would do the same with a Brenneke. Butmine just would not shoot those Brennekes at all.

Yes, you CAN shoot thoseFoster-type rifled slugs in a rifled barrel. In some gunsthey shoot very well, in others, they crud up the bore real fast with LEAD! When this happens, they stop shooting accurately.....

IF I owned a rifled bore deer "shotgun", I would not handicap it with 1930's technology (Foster "rifled slugs"). I would use the best available (the one that shoots best in my barrel!!) modern sabot-type "bulleted" shell.......

Range: The Foster-type slug is pretty much finished by the time it gets to 100 yards, max. The bulleted-sabot type from a rifled barrel might be OK to 150, and maybe even 200 yards. BUT, remember, ALL single-projectile shotgun cartridges use bullets or whatever that are designed to poop out before they've gone very far, since most places that require shotguns for deer do so for safety reasons. They don't want bullets or slugs flying into the next county!