As a victim of a public education in the great State of Missouri K - post-graduate
I'm not so good with numbers. I think we are all just trying to understand, despite we and the British speaking a different language
A not unreasonable summary, which Bro. Bruce has been telling us for years, is that
there is no reason to believe turn-of-the-century Bulk (and esp. Dense) Smokeless Shotshell pressures were much different than today's loads.
The fluid steel and pattern welded barrels were not 4140 however, many are now 100 years old, and some were neglected or abused. I think we also understand our margin for error is less.