In the beginning, the "standard" 28-gauge load in the U.S. was 1 3/4 drams equiv. and 5/8 ounce of shot in a 2 1/2 inch shell. RST is currently putting up a lovely little recreation of this shell. The Super-X 28-gauge shell came out in 1932 with 3/4 ounce of shot in a 2 7/8 inch case and the pre WW-II Model 12s and Ithaca and Parker Bros. doubles were chambered for this caseb. After WW-II the 28-gauge loads began being put up in 2 3/4 inch cases, and post WW-II Model 12 28-gauge guns were chambered for 2 3/4 inch shells.
Actually, clear back in his 1910 book The American Shotgun, Chas. Askins writes about handloading 3/4 ounce 28-gauge loads in 2 7/8 inch cases for his 6 3/4 pound 30-inch barrel Parker Bros. 28-gauge gun.
