Buckhunter - I've been doing alot of reading and testing different slugs in my 870 (see my post in this forum). The Federals with the Tru-ball worked best for me. But this is a smooth bore not a rifled barrel. You may want to try some of the newer saboted slugs in your Mossberg rifled barrel. They may give you better accuracy. Many of the others like the Rem. Sluggers have rifling on the slugs themselves that isn't needed with your barrel. Even with the smooth bore like mine I don't believe this 'rifling' on the slug does much good. Good luck and good shooting.