I've never tried it, but from what I have read/heard, you pack the wadding into the cartrige case, NOT the barrel.

Seems to me, if you had a pretty short barrel, like a 2" .38 or something, you MIGHT be able to pull the bullet, dump all of the powder into a pile on your tinder, put the muzzel close, and pull the trigger. The flash from the primer MIGHT light the stuff off. Last ditch effort in my opinion...