I know this may be blaspheme to many, but I have to ask. With powders such as American Pioneer and Triple Seven being so easy to procure, has anyone had good success using these powders in a flinter? I'm talking about using a good authentic black FFFG or FFFFG priming powder, and maybe perhaps a few grains of the same down the bore as a sort of "spark plug" load to light off the main charge of one of the replacement powders? Ok, I'll sign off with that and put on my manure resistant rain coat for all of the stuff that will be no doubt flying my way.
If you're switching from a BP substitute as I did when I switched to Flintlocks, I went from Pyrodex RS to Goex and had a few lbs of Pyrodex left over that I did not want to waste.
I tried layered loads of 20grns Goex down bore, followed by 50-60grns Pyrodex RS...worked perfectly, accurate, consistent, etc, and I used up some of the Pyrodex.
However, I soon tired of fooling with the two different types of powder, the extra time involved, the chance for error, etc, and after a couple range trips, stopped doing it.
The good news is I later got a .12ga SxS percussion smoothbore and I'm using up the leftover Pyrodex RS that way.
If you can't find real BP locally, a couple places sell loose cans with a 5 can minimum...like Graf & Sons, or PowderInc...that's how I got started...ordered a can of FFFFg and half dozen cans of FFFg.
If you ever switch to something like Goex, you'll never go back to BP substitutes...it has four outstanding qualities: It's fast, clean, accurate, and reasonably priced...Enjoy!