If the slug barrel is smooth (no rifling) then you should not use Sabot slugs as they will not stabilize and your accuracy will be poor.

With a smooth slug barrel (no rifling in the barrel) Foster type slugs are best. Some of the packaging will read "rifled slugs" this means the slug itself has groves cut in it. The reason for this is so that groves in the slug will catch the wind as it travels downrange and impart some spin in order to stabilize the slug.

Now if the barrel is rifled then either foster or Sabot slugs can be used. Sabot are recommended and are more accurate, they should shoot pretty good out of most standard rifled slug barrels. All boxes of Sabot slugs will say "Sabot" on the box somewhere.

If you are indeed using a rifled barrel and Sabot slugs....And are still getting bad groups I'd suggest trying different brands of Sabot slugs to see which will perform the best. Remember size and velocity can differ greatly with Sabot slugs on the market today and not all will work with thedifferent rifle barreltwist rates out there, Find the ones that work for your particular barrel.

Good Luck.