Researcher;
Great info. I too had often wodered about the pressures of some of loads you mention. I could not help but believe they had to be quite high, much higher than we have so often seen implied that all the older loads were. Some of the pressures you state exceed present day SAAMI Specs. Some of these very loads were listed in Lefever Arms Co catalogs with no distinction made as to their use in either steel, twist, or damascus bbls. Many shooters of the era also used a comparatively fine graind black powder which itself was no pussy-cat for pressure.
At least as early as 1913 the LACA catalog stated all their 12ga guns would be shipped with 2" chambers unless otherwise ordered. L C Smith had gone to 2 3/4" for their 12 ga guns even earlier.
I realize that some early shells did not have a very high base wad, & I have not tried it but with a 3˝ dram measure & 1Ľoz of shot one would not get much wadding in a hull shorter than 2 3/4". The smokeless loads would have fit the 2 5/8" hull much better I would think, but those early smokeless powders were all quite fast burning, thus high pressures with heavy shot charges.
