It's my understanding, that back in the days of black powder, the quartermaster would have a "proof gun" (this may not be the correct term), which was a pistol-like contraption which had affixed to it a lever and a scale which when loaded w/ a known weight of black powder would then provide a measurement of its relative strength / potency so that a given batch could be used safely / most effectively.
My son is building such a thing as his science project for the year, but I'm not finding any historical examples.
Does anyone have any references, links, or other helpful information? Just having the correct terminology might be helpful, since searching for "black powder proof gun" mostly turns up discussion of proof-firing a weapon and proof marks.
And searching with a clear mind reveals the term "eprouvette" (Fr. for test tube) and a useful link at: http://firearmshistory.blogspot.com/...r-quality.html
I'd still be glad of any other references or thoughts anyone might have....