Logic would dictate that, using the correct projectiles, in a gun with chambers in good condition, there's no way that I can think off that a spark could get into the powder from the front end. Mine shaves a small ring of lead off when seating the bullet, so there's an interference fit there.
Using an undersized bullet might make a difference but I can see where you're coming from Tac.
However, I'm a belt and braces man (I use spring washers AND locktite on threads ) so the addition of a semi greased felt wad can't do any harm and spaces the bullet out a little.
I've not been using black powder for as long as you have Tac but I must be doing summat reet as I've been at it (on and off) since the mid seventies and I still have all my fingers.
Cheers