Old-Win, i wasn't ever that great a shot, although I can still keep the signal-to-noise ratio consistent enough off the bench to test ammunition and do experiments. And no shooter has more fun than I do.
I also wondered about the potassium nitrate report. The main impurities in “bad” KNO3 are chloride and sodium, from the substitution reaction. The sodium ion attracts moisture, caking the powder.
Everything I’ve read on high quality black powder involves the extent of “incorporation” done on the mixture. Kinetic phenomena like burn characteristics go all over the place to the direct extent that the ingredients aren’t evenly distributed through the mixture.
Incorporation is done on rolling mills; the old-time ones had the two stone wheels twirling around the circular stone track. It isn’t grinding or mixing, as those operations are understood. Incorporation presses the particles of sulfur into the pores of the charcoal. Dampening and more incorporation gets the saltpeter into there also.
Doing this under expert observation and management is expensive in proportion to how long it goes on. There are stages where it is “good enough” for an application: blasting, fireworks, safety fuse, mil-spec stuff, musket powder, sporting powder, etc.
Black powder that’s good enough for blasting can be made with all sodium nitrate. The other powders would need purer ingredients, and I’m sure the descriptions by the Mad Monk and others of the creosote content needed in the charcoal are true, but the bulk of the effort, and expense is the incorporation. Getting a mixture like this truly homogeneous (enough, for instance so an expert shot can’t notice variances in burn characteristics on the target), while still mixing slowly enough to not create a safety hazard, can take a surprisingly long time.
I was told once that if I wanted a Volkswagen Bug (the old, air-cooled model), to get one that was made before 1966. “After that, they went General Motors and the quality went down.” The new ones looked the same, but little nuances like the cruising speed being the top speed weren’t there anymore, he said. Maybe the Swiss outfit tried to scale up or streamline production in some way. One could assume that the better the incorporation, the higher the density of the resultant powder as all the pores in the charcoal would be filled completely.
The nice thing about the old lots was that a good load could be worked up without a lot of finagling, and the same load would be good with the next lot I got. If it’s now down to the same effort and uncertainty in development work as any other powder, the higher price simply isn’t justified.