In North America, the "standard" 16-gauge shell was a 2 9/16-inch case with a maximum load of 2 3/4-drams of bulk smokeless powder or 22-grains of dense smokeless powder pushing 1-ounce of shot. From the 1905 Union Metallic Cartridge Co. catalog --
Our ammunition manufacturers would put these loads up in longer cases of 2 3/4-, 2 7/8- and 3-inch, with more/better wadding.
The progressive burning smokeless powder, high velocity, loads in 12-gauge 1 1/4-ounce and 20-gauge 1-ounce were introduced by Western Cartridge Co. in 1922 as their Super-X load put up in their 2 3/4-inch FIELD shell.
In late 1922, Western added the 16-gauge Super-X load of 1 1/8-ounce, but put it up in the 2 9/16-inch shell.
The other ammo manufacturers followed suite, Peters with their High Velocity and Remington with their Heavy Duck Load (which soon morphed into Nitro Express).
The 2 ¾-inch 16-gauge shell really began to get some traction when Remington Arms Co., Inc. introduced their Model 11 and "Sportsman" autoloaders in 16-gauge in 1931, chambered for 2 ¾-inch shells. While Remington's regular Nitro Express 16-gauge progressive burning powder load was put up in a 2 9/16-inch hull with a load of 3 drams equiv. pushing 1 1/8 ounce of shot, for their new 16-gauge autoloaders they introduced the slightly faster Auto-Express with a 3 1/4 drams equiv. charge pushing 1 1/8 ounce of shot --
The 2 ¾-inch Magnum shells with 1 1/2 ounce in 12-gauge, 1 1/4 ounce in 16-gauge and 1 1/8 ounce in 20-gauge first appear in the December 15, 1954, Western Cartridge Co. catalogues.