Jay the actual bullet is encapsulated in what is basically a plastic cup. When fired the plastic cup (with the bullet in it) travels down the barrel for approximately .0013333 - .0010000 seconds in shotguns with ammo rated 1500-2000 fps. In this time the plastic cup (sabot) is fitted tightly against the rifled sides of the barrel and the twisted rifling (roughly 1 full twist in anywhere from 24 - 36") gets the sabot and enclosed bullet spinning. It is this spinning that actually stabilizes the round. The sabot picks up air around the edges and peels it back, opening it much like a flower blooms until it falls off the back of the actual bullet.

The only sabot round I know of which acts a little differently is Lightfield's IDS slugs which peel the sabot upon impact.

IDS = Impact Discarding Sabot.

Hope this clears things up. If it has, allow me attempt to get you confused all over again. I don't shoot sabot-slugs thru my rifled slug gun.

Now let me confuse you