While Ithaca would chamber for longer shells if the customer requested, normally the 16-gauge was chambered for 2 9/16 inch shells and the 20- and 28-gauge for 2 1/2 inch shells. When the 20-gauge progressive burning powder, high velocity, 20-gauge 1 ounce loads hit the market in 1922, Western Cartridge Co., Peters Cartridge Co. and Remington Arms Co., Inc. put up their versions in a 2 3/4 inch case. So, Ithaca may have begun chambering their 20-gauge guns for the 2 3/4 inch shells before the catalogue text caught up. Winchester like the others put their 1 ounce high velocity 20-gauge loads in a 2 3/4 inch case, but with all their 20-gauge Model 12s in the hands of sportsmen made for 2 1/2 inch shells, they also stuffed the load in a 2 1/2 inch shell.
