I'm not a a firearms expert, but the the muzzle flash looks very different than anything I've seen. . .in the pic it looks like a brightly lit cumulus cloud. . .and its projecting straight forward. A number of weapons have "flash suppresors" which distribute the muzzle exhaust perpendicular to the barrel, at its end-- I have no idea if the weapon you're using does so, but its a neat effect, and widely used in firearms shots for film. . . Also, the exhaust should appear to be lit from within. . .