I have not made any weapons so I know very little about it. However...
If the chugshot can have that blue thing swirling around, then why can't the flames be animated as part of the gun?
The shoot would animated the flames out of the gun like a recoil action does on shoot for regular guns.
The flames swirl all the time, you just dont see them until it pushes them out of the barrel through an animation when fired.
After all, its not that far from the end of a gun barrel to the center point of the screen.
You'd just need a fat barrel to hide the flame in.