It wont take a spark very well to ignite. I guess you could...but you would be pretty frustrated trying to get it to go off. 2F burns much slower, and you want that pan to catch quick and burn fast...so FFFF or 4F is the ticket for the flash pan. 2F or 3F for the propellant charge.
Think of it this way.Blackpowder is Blackpowder reguardless of "F" size.
The "F" is the size screen it passed thru.Kinda like Fg is a log,FFg is a spilit log,FFFg is kindling,and FFFFg is sawdust.
All wood but different sizes and different burn rates.
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