I looked over Greener, but unfortunately, he uses Curtis & Harvey granulation numbers (6 vs 2) to describe the powders in question. He says the load that blew the gun was a full charge of a "very fine grained" powder. I've never played with 3Fg, so I can't comment if that qualifies as "very fine."

Greener refers to detonation of black powder in big cases, but more modern sources say this never happens; it's just not part of the chemistry of black powder.

I'll note one muzzle loader guy say 1F is too slow for 500 gn .45s, that 2F is about right (up to 100 gn or so), and that 3F can work in some rifles.

I'll keep reading and post back here. I must try to locate a copy of Seyfried's articles on the subject; I've always admired his work.

Karl