I suspect the boys at Chicopee Falls didn't spend a lot of time checking the regulation on these entry-level doubles. Some other likely problems could be if your Springfield No. 311 was made from their introduction in 1929 to 1934 --



it was likely originally chambered for the 2 1/2 inch .410-bore shell which in those days contained 3/8 ounce of shot. Modern day shells may just regulate differently then the shells at the time.