If your using an inline it will work fine.They give a hotter,more direct flane to the charge.
In a flinter,stick the real Goex Black Powder.
Blackpowder gives faster ignition because of its lower flash point.
Okay.....I'll bite. 90gr. 2f 777 with 5gr fff BP. In a Lyman GPR. Been shootin it for years now and have had no ignition issues at all. I like the ease of cleaning. Use it in the TC Encore inline also w/o issue.
It's all in what ya like and what works for you. I must add that I never had ignition issue with BP either and the smoke/smell was great too!!
Here too, used black for about 23 years and switched to 777 about 6-7 years ago. I notice a slightly longer delay than with the black but I haven't tried the black primer charge yet. Never had an instance when the pan went off that the main didn't. Took my longest deer shot this year with 90gr 3F T7 and a PB 338 Platinum, haven't ranged it yet but I know where 200 is so the shot should range at about 180. MV is 1630fps, I zero at 100 and pattern it at 150, 6" low. Took a big NM bull elk in Sept with this load and am seriously considering using it for an upcoming Newfoundland moose hunt.
Use what you want. Having said that I use good old Gooex in all my muzzleloaders. The reason for that is the ignition point of real BP is around 460 degrees while all the substitutes have an ignition temp of over 700 degrees. A flintlock has the weakest fire of any ignition system. I had a real problem with ignition using APP in a sidelock.