I, personally, would go for the Iver long before I even thought about a CVA. "Choke bore" means full choke, which was normal on old single-shots.
There are two types of slugs. Sabot and Foster.
You want the Foster kind. Sabot slugs are for use in rifled shotgun barrels. They don't work for beans in a smoothbore.
Brenneke slugs are a Foster-type, with a wad attached to the backside. I think they are the best of the Foster type, but they do cost more.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.