When I first tried it I used a mix of 2 3/4 inch shells and some 3 inch steel bb. It didn't like the cheap Winchester 2 3/4 inch shells from Walmart. It fired them though. When I went goose hunting I used Kent shells in bb. Not sure if they were over 1 1/4. No jams or anything. The gun worked well. It was cleaner to clean than my browning gold. With those gas ports it has out the side I think help.