While most of our ammunition companies put up their progressive burning powder, high velocity, 20-gauge, 1 ounce load in a 2 3/4 inch or longer shell, Winchester also stuffed the load in a 2 1/2 inch case --

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

probably because there were so many sportsmen in the marketplace with their Model 1912 20-gauges made for the 2 1/2 inch shell.