On topic, the cheapest 12 guage slug rounds I've found for target practice are the wolf rifled found here:
http://www.abcoutdoors.com/home.php?...oduct&id=35066
Brenneke usually are the cheapest, but they are out of stock everywhere. Maybe they discontinued the KO line. I don't know.
Oh, and the rifled(foster) slugs work on smooth bore better. The sabot rounds work in rifled barrels better. Don't use sabot in a smooth bore. I hear it could be bad. The brenneke and other rifled on the slug varieties work best as a slug in smooth bore as compared to a solid ball. I notice that the recoil is lessened with rifled/ribbed slug rounds.