I have been shooting flintlocks for quite awhile and I have loaded the pan from the priming flask for many years!
I started out using FFFFg for priming and I've stuck with it.
Well, I can't say I have
NEVER loaded the pan from a horn before because I can remember priming from a little flat primer horn many years ago....but that was a hit and & miss affair because I never put the same amount in pan each time, and I got a lot of pan flashes back in the early days.
I "think" my first priming flask, dispensing 3-4 grs FFFFg, came from DGW, about the same time I got my .69 smoothie....which would have been in the mid 1970's....It was advertised to be the greatest thing since sliced bread, but so was the old Ultra-Hi that I bought at the same time.
Turner Kirkland must have sold a boat load of those old Ultra-Hi's, at less than 100 bucks each they were in demand, and many of those old guns are still around.
(I strongly suspect the reason the old Ultra-Hi' are still around is because they were made in Japan by Miruko, a very high quality name when it comes to all manner of firearms, even to this day.)
I like the idea of one powder for everything, but my brass priming flask is so small I carry it on a leather boot lace around my neck, it always there and it's always handy "without" ever having to put the plug back in it each time.
I've never measured just how much that little primer will hold but I guessing well over 100 / 150 grains.....dispensing 3 gr of FFFFg at a time it seems to last forever, much like a full can / pound of FFFFg, it's very much akin to that Energizer Bunny, it keeps going, and going, and.....
Uncle Russ...