Been looking all over the interwebs but haven't found any pressure data for original black powder 12 gage shotgun shells.
I have two Hopkins and Allen falling block 12 gage shotguns in good working order but I am curious to what pressures these old shotguns worked under and as well as what breach thrust pressure would be. The older of the two shotguns was made between 1888 and 1898 and has the side takedown screw. The newer one was made between 1898 and 1908 with the bottom takedown screw. And no, I haven't tried shooting them.
I suspect chambers to be 2 5/8" but will measure and make sure. I read a post here that breach thrust was in the range of 6500psi. Can anyone confirm this?