To Piggy back on Klawman's question... My rifled barrel 20 gauge has stamped on it...use sabot-slugs only
. I take that as a pretty serious warning from the factory.
On the other hand My Saiga smoothbore 12 will do 4 inch groups at 50 yards with old-style slugs (1 oz) although I hope I don't need a 'group' for the smaller Whitetail we are seeing here in Indiana this year. Having a ten round mag full of slugs can do a job on a small critter if they **** me off !