I am not sure Dupont ever made a premium BPO like Orange Extra or C&H Diamond grain. There were at least 2-3 really good powders made in the US in the late 19th c. I pulled the bullet from 38 S&W BP load and it was loose in the cases. Very fine grained, probably what used to be called “Revolver”. Very shiny with no evidence of “black lead”. I think this was a UMC but its been some years ago now and fool like I did not write it down and it belonged to a friend.
There was a brown powder made by some US maker that was supposed to be really good. And the Slug Gun and the BPCR target guys were REALLY finicky about powder. They, some at least, were known the resift the powder the make for a more consistent grain size. This effects flame propagation through the charge and can effect accuracy. As does milling time, how hard the cake is pressed and what the charcoal is and how it is charred. The Charcoal charring and the species of tree and even when in the year it was cut were critical. There were Americans who only used C&H Diamond grain. Which is VERY, VERY different than the C&H that was imported to the US in the 1960s and 70s. This stuff was essentially blasting powder and could very easily have been contaminated with Sodium Nitrate. Since it was made in a plant in Scotland that made blasting powder. Or so i was told by Bill Knight. Bill considered Swiss to be the nearest thing to the old premium powders. And probably is that good. Good as Diamond Grain I doubt but is pretty close.
