Per Researcher:

In 1922, Western Cartridge Co. intoduced the 'Super-X' 12 gauge 3 inch shell with 1 3/8 ounces of shot, and the 2 3/4 inch 1 1/4 ounce 3 3/4 dram equiv. load. Peters Cartridge Company's 'High Velocity' and Remington's Kleanbore 'Nitro Express Extra Long Range' loads soon followed. In 1935, Winchester/Western brought out the 1 5/8 ounce 12 gauge 3 inch magnum.

Last edited by Drew Hause; 09/10/11 08:56 AM.