I've never heard anything bad about shooting rifled slugs through a rifle barrel. Before the sabots came around, the rifled barrel was the step up in accuracy for the foster slugs.
I went back to foster slugs from the high dollar sabots, and I can still get 2-3" groups at 100yards. Energy is higher with the fosters too. Federals have always worked well for me, but another guy at our club that has the same results with fosters/rifled barrel has great luck with Winchester.
Charlie