I've been shooting blk pdr for over 50 yrs so your warning is certainly wasted on me but maybe not on others. Thought I made it very clear that I am just looking for something for the F/L priming pan & your idea of mixing sulfur may work. Hopefully I don't have to resort to that experiment but will remember it. Incoming reveals that I have to have the right type of sulfur.
I got in touch with a friend who has a plant nursery about getting the proper ingredients and he has a blk pdr Colt he doesn't shot & said if he can find the pdr, I can trade my merde for his. Of course I don't know if he has true blk pdr until he finds it. Also, walking in my house, an old powder flask in a shadow-box of mine caught my attention. Took it out and sure enough, it had enough pdr for a good 20 pans. I work with the musee's in 2 countries & thinking about ck'ing those flasks(1 I even donated).
Thanks for the sulfur input as I may have to try that.