ALL SST "slugs" are actuallyHornady SST BULLETS, loaded into plastic sabots of essentially the same kind as are used to shoot those same type of bullets from muzzleloading rifes. The main difference is that the sabots made to hold the bullets inshotrgun ammo have an outside diameter that fits the shotgun bore.

Since elongated bullets require a spin to remain stable and fly point-forward, all such "slug" loads MUST be fired in a rifled bore.

(I just went to the Hornady site and looked at the ballistics of those loads. VERY impressive! Much more power than needed for just deer. Those would work well on elk or moose too, maybe even big bears! I may have to buy a rifled shotgun!)