... especially considering that so many of these guns continued to be used long after the low pressure ammunition they were designed to digest was no longer generally available?
FWIW, the Remington Hammerless Doubles were said to be "guaranteed for nitro powders" from their introduction in 1894. Up to at least 1905, the heaviest loads available from our North American ammunition companies in the 12-gauge 2 5/8 inch paper shells was 3 1/4 drams of bulk smokeless powder pushing 1 1/4 ounces of shot. By 1910, our loading companies backed off the loads offered in the 2 5/8 inch paper shells to a max of 1 1/8 ounce loads, and one needed to go to the 2 3/4 inch or longer shells to get the 1 1/4 ounce loads. A surviving hang tag for a 1908 vintage Remington KE-Grade says it was targetted with a UMC Nitro Club shell 2 5/8 inch, load X8, with 24 Grains Infallible and 1 1/4 ounces of shot. I don't have access to a 1908 UMC catalogue, but the January 1907, and June 1909, shows load X8 to be 24 grains of Infallible pushing 1 1/4ounces of shot, and coming only in a 2 3/4 inch Nitro Club shell?!?
The heaviest smokeless powder loads offered in the 2 3/4 inch and longer 12-gauge paper shells were 3 1/2 drams of bulk smokeless powder, or 28-grains of dense smokeless powders such as Infallible or Ballistite, pushing 1 1/4 ounce of shot.
According to a couple of DuPont Smokeless Shotgun Powders booklets I have in my collection, these were quite stout loads, the various bulk powders going 11,700 to 11,800 pounds and the 28-grains of Ballistite a whopping 12,600 pounds.
Many, many lighter loads were offered, but we "know" that North American Nimrods being as they are, that plenty of them were loading their guns up with the heaviest loads available.
When progressive burning powders, developed during WW-I, were applied to shotshells, Western Cartridge Co.'s Super-X loads leading the way in 1922, they pushed that 1 1/4 ounces of shot out of a 2 3/4 inch 12-gauge paper shotshell at considerably higher velocity, and actually lower pressures than the old bulk or dense smokeless powders were capable of.
