
I've shot a deer with a 20 smoothbore with single bead at 60 yards, my first, 12g smooth with single bead at 45, and 20g rifled barrel with scope from 7 yards to 93.
It blows that this state won't allow a 20g for elk as they are just as effective as a 12. IMO
If you are buying, and not hunting elk, Mossberg (500) makes a nice combo with a smoothbore and a cantilevered scope mount rifled barrel. They also make a rifled barrel with fiber optic sights which is easier to find but then you have the potential limitations of this type of sight, which I personnaly do not like as much as a scope.
Just remember, if you shoot a smoothbore, you need rifled slugs. I think you can shoot rifled slugs from a rifled barrel but you get better performance out of the saboted bullets. If shooting buckshot, you want a smoothbore as a rifled barrel may spin the shot out of any decent kind of pattern. I would not shoot at a deer much past 40 yards with buckshot, and that only after patterning to make sure I had a pattern not much bigger than 6-8", but that's me.