I highly recommend using Foster type slugs. If you keep the powder load moderate they are MUCH more accurate than round balls. The only problems I've experienced with them are the "maximum" or high speed loads which, I believe, are erratic due to the base skirt being blown out by high pressure when the slug leaves the muzzle. I've shot them from improved cylinder and modified chokes in a couple of pump guns with no problem and with excellent accuracy out to 75 yards or so. The "rifling" doesn't really spin the slug but lets it squeeze through a choke, while the hollow base stabilzes it.
