You can shoot Foster ("rifled") slugs. The problem, though, is Foster slugs are very soft lead so they can squeeze through a choke. The very soft lead melts into the rifling, leading your barrel very badly.
When I worked at Gander Mountain years ago, I would explain it to customers like this: Only one of the components (barrel or ammunition) should be rifled. Rifled barrel = no rifled slugs. Smooth barrel = rifled slugs.