M79 Grenade Launcher Replica - 40mm Shell PropM79 grenade launcher is single shot, shoulder fired, and break action. It fires a 4046mm grenade, which uses what the US Army calls the High Low Propulsion System to keep recoil forces low. This historical weapon first appeared during the Vietnam War. This is a science fiction prop gun. This M79 prop is just a toy and doesn't actually shoot anything. It has no moving parts. Use it for cosplay or scifi movie making. Full Scale (Life Size): 27. 3" x 5.