I never had to put 4f in the barrel to light off pyrodex. I was hoping to find a cleaner burning, noncorrosive substitute.
777 is less corrosive and cleaner, but like Pyrodex, the manufacturer recommends a 5grain FFFF booster under the main charge for flintlocks. It also doesn't keep well and after a few shots you may need to knock out the crud ring just forward of the chamber, unless you're shooting well-lubed PRBs.
You have choices, but none of them give you everything you want.
