Shot generally expands about 1 inch per yard of travel, which translates into a plate-size pattern at the end of the hall
Although one time I did absent-mindedly shoot buckshot through a rifled 12-guage barrel (which is designed for rifled slugs). It produced a yard-wide doughnut pattern at 7 yards, due to the spin imparted to the buckshot.
Interesting. I will definitely have to do some more research!