This will be my last post on the subject. I'll bet a lot of readers are baffled by all the numbers shown in many posts on this thread.
An analogy that comes to mind here would be: for someone to take automobile engine horsepower ratings from the 1920-30's or so, and try to compare with modern engine horsepower ratings. Yep horsepower is horsepower. But that person has no idea if the dynamometers (if any) used back then were all calibrated from auto maker to auto maker and if the results obtained with that relatively primitive equipment and converted from torque to horsepower are all dead nuts accurate - as compared with current horsepower ratings made using modern technology.
Why does this analogy at least partially fit? Because many of us are using vintage SxS shotguns and are relying on period lead crusher ton or even period psi pressure numbers to cipher what we can shoot in them relative to modern transducer psi ratings. But when using those period pressures no allowance is being made for the relatively simple gunpowder manufacturing technology back then and even small differences in % of nitrogen (money number) in various lots of the powders, addition/deletion of powder additives, and advances in shotshells such as roll crimps morphing to star crimps, different wadding materials over the years. etc. On that line it's no different than looking at a modern shotshell loading manual for a specific powder charge weight and hull, and seeing the differences in pressures by substitution of alternate primers and wads.
Sorry for my rambling here, but I come back again that a good approximation of vintage lead crusher numbers to modern psi, may be made by taking the tons/sq inch X 2240 X 1.10. This will yield a number that hasn't been enhanced by the addition of yet another conversion factor that, in sum, might make gents think that certain vintage shotguns and barrel materials were designed for higher pressures than they may have been.
FINIS
frank
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