As a 25yr Infantry veteran I can tell you that the visibility of muzzle flash from a modern weapon is little to none due to the effectiveness of the flash suppressor at the end of the barrel. It is most definitely not visible by the shooter while looking through iron or optical sights. The amount of illumination the current game shows due to muzzle flash is highly unlikely in RL. There are many YouTube videos showing the effects flash suppressors in the dark of night including the very primitive slant suppressor on an AK-47. And not a single one produces the amount of flash that they do in game. The reason Hollywood weapons produce such a flash is due to the flake type of gunpowder used in the blanks that burns very slow producing flame. A modern high velocity round uses grain powder that burns extremely fast thereby producing very little flame.