The 2 3/4 inch 12-gauge shell was the standard shell for all of the 20th century in North America. The Winchester Model 1897 was made for the 12-gauge 2 3/4 inch shell. The Remington Autoloading Gun, from its introduction in 1905, was made for the 2 3/4 inch 12-gauge shell. Many of our North American firearms manufacturers had the policy of holding their chambers 1/8 inch shorter then the intended shell. This is clearly spelled out in the Remington era Parker spcification sheets in
The Parker Story on pages 164 to 169.
Western Cartridge Co. introduced the Super-X shell, loaded with progressive burning powder, in 1922, in both 12- and 20-gauge in a 2 3/4 inch case. The 12-gauge load was 3 3/4 drams equiv. and 1 1/4 ounces of shot and the 20-gauge load was 2 3/4 drams equiv. and 1 ounce of shot. They also introduced the 12-gauge 3-inch Super-X with 1 3/8 ounces of shot pushed by 4 drams equiv. of progressive burning powder at that time. The term "Magnum" first appears in North American shotgunnery in 1932 with the introduction of the Ithaca NID Magnum-Ten for the new Western Cartridge Co. 3 1/2 inch Magnum-Ten shell. The 12-gauge 3-inch "Magnum" came along in 1935 when Winchester introduced their Model 12 chambered for a 3-inch 12-gauge shell, and Winchester and Western upped the payload in their 12-gauge 3-inch Super-Speed and Super-X shells to 1 5/8 ounce of shot pushed by 4 1/4 drams equiv. of progressive bruning powder and called them 3-inch magnums. When the 16-gauge Super-X shell came out in 1923 it wa put up in the old 2 9/16 inch case, with a load of 1 1/8 ounces of shot pushed by 3 drams equiv. When Remington introduced their Model 11 and "The Sportsman" in 16-gauge in 1931, they were made for 2 3/4 inch shells and Remington introduced a 2 3/4 inch 16-gauge shell called the Auto Express which carried a load of 3 1/4 drams equiv. and 1 1/8 ounces of shot.
The old 2 5/8 inch 12-gauge shells and the 2 1/2 inch 20- and 28-gauge shells disappeared from our ammo catalogues with WW-II, but the 2 9/16 inch 16-gauge shells continued to be offered until about 1960 or 61.