For those with the interest, the last article in John Brindle's series in The Double Gun Journal, “Black Powder & Smokeless, Damascus & Steel” was in Volume 5, Issue 3, Autumn, 1994, “Some Modern Fallacies Part 5”. He discusses in detail the progression of black and smokeless proof, but has very few pressure numbers.
This is one of his conclusions:
"The pressures produced in the breechloader by black powder, as black powder was actually loaded at the end of the 19th century, were not significantly lower than those given by smokeless (then often termed “semi-smokeless”) powders developed as a substitute for, and an improvement on, black powder."
Our local library obtained a PDF copy of the entire series for me in 2016, but it is under copyright by DGJ so I can't share it.
