madsenshooter wrote on Dec 10^th, 2016 at 8:21am:

They didn't always use 40gr of powder.

Even for the early military loads this was true. At google books one can read several of the Army Ordnance Reports from the 1890s. Frankford was testing loads from under 30 gr to well over 40 gr, depending on the powder and lot. Peyton was the principle powder loaded until that powder plant in California blew up. I think WA replaced it eventually, probably about 1899.

I imagine commercial loads from after WW-I likely used the earliest IMR powders. Whelen praised them in his book written during the war--a book also available at google. Pre-war loads might have been WA, or they might have been MR, or some other powder yet. Whelen's book gives some of the kernel dimensions as well as loads for several powders.