[T. O'Heir]

Sabotted slugs require a rifled barrel.
A rifled choke tube is kind of old technology. They were made before the manufacturers started making fully rifled shotgun barrels. Made for regular slugs not sabotted slugs.
You can expect 2 or 3 inch groups at 100 with a smooth bore using slugs and iron sights. Some shotguns are scary accurate with 'em. You do have to try a box of as many brands as you can just like a rifle or handgun though.