20mm cannon on German AFV. No muzzle flash.

http://www.youtube.com/watch?v=Y-B96xZ8Tyk

MG-42 firing multiple bursts (7.92mm). No muzzle flash.

http://www.youtube.com/watch?v=AwW31u6wYvE

Vickers .303 firing multiple bursts. No muzzle flash.

http://www.youtube.com/watch?v=HeycW...tailpage#t=82s

Unless I'm mistaken, that's all of the main rounds used by both sides. 20mm and 7.92mm for the Luftwaffe and .303 for the RAF. So they should not be visible during the daylight, but should at night.