I shoot them at the enemy if I'm almost out of ammo. Not sure if it does any harm but I hate to let them go to waste. I fired one accidently at night near a convoy once when I first started to play the game and it was useful to the enemy. Plus I like to make my night departures and arrivals a bit more dramatic for the band and fraulines so a couple over their heads always brings a tear to everyone's eye.
