To realize the full potential of a rifled barrel your probably going to have to pony up for sabots(Rem Copper solid, Win parti gold, Fed Barnes Expander) or stablized slugs(Lightfield Hybred, Rem Buckhammer).
My Marlin 512 has a 1 in 28" rifling twist and likes the sabots best. My Browning A-bolt has a 1 in 35" twist and likes the stablized slugs better.
I have been able to get away with using cheap Winchester Super-X rifled slugs to sight in with but accuracy with the high dollar slugs designed for rifled barrels is improved enough in my guns to make it worth the $$$.
I do my sighting-in work at 50 yards to avoid wind problems that all slugs suffer from at 100. I must be the only one to notice this because I read all over the net about how some $40 single shot can shoot sub MOA @100 with Remington Sluggers:)