No interest in trying subs in a flintlock...Black powder is charcoal, potassium nitrate and sulfer...The sulfer lowers the ignition temperature...
Pyrodex came out in the 70s, it was made with a higher ignition temperature so it didn't have to have all the government regulations on shipping and storage that real black powder does...
Since the ignition temperature is higher, it's harder to ignite with sparks from a frizzen...
Nope, not trying it...No need to have to pull a charge for experimenting when real black powder works just fine...