I recall seeing photographs of a Madbull prototype. It had a series of long slots on the side to allow light to show through for the muzzle flash effect, and a slotted outer cover which, when rotated, would either cover or uncover the slots.
Personally, I've found that firing tracer BBs does enough to call attention to one's self during a night game. You really don't need to add simulated muzzle flash.
