There was no thought of a substitute while the flintlock was king. Most all of the substitutes came along rather recently since the advent of the inline and especially when they started using the 209 ignition. Black powder ignites at about 460 degrees while the rest of the subs require from 600 to 800 degrees for ignition. That is primarily why real black powder is still best for the flinters. Black powder is not the least powerful though as APP has that honor according to Hodgdon. The real stuff is all I use and it gets the job done in flintlock, side lock and inline.