If you REALLY want to see a spread pattern, once by mistake I fired buck through a rifled barrel meant for slugs. Hit the target in a doughnut pattern.
Actually, I have a rifled choke tube in my 20” iron sighted Rem 870. It will shoot slugs in the black at 90 yds. and still pattern buckshot well at 30 - 35 yds. I keep it handy at home for that reason.
If you were shooting a fully rifled slug gun I suppose that might give the shot cup a pretty good spin though. Bet that was ammusing to observe.