ORIGINAL: Grunter Hunter
Well, welcome to slug-shooting! You can also buy the 'rifle slug' screw-in chokes so you can shoot the saboted slugs. The screw-in choke has the rifling in it for the sabots.
Mossberg does not recommend that! Their barrels are Back Bored and some Over Bored. They recommend that you use Improved Smooth with Rifled Slugs or Rifled Barrel with Sabots.