HI, Interesting idea. Here's my 1 1/2 cents worth, and that's probably about all it's worth too. Ha! About the only thing I can think of at the moment would be to add some thin plastic or PE strips--painted the appropriate colors--coming out of the barrel. Super glue these in place and have your 'smoke' intertwined with this to give support to both the 'smoke' and the 'flame.' Now not every having attempted something like this, this may be way off the mark, but it may be worth experiemnting with just to see if it looks real or not to you. Since this 'flash' of burning powder is a momentary thing, there wouldn't be all that much of it showing, just enough to give this area some color of flame inside the smoke being generated. Just a guess here.
A really neat idea. Keep us posted on this.
Good luck and take care, Sgirty