One of the primary drawbacks of a conventional firearm is that it wastes so much of the explosive force it created in order to propel a bullet out of the barrel with the hope of hitting a target. The majority of this precious motion force and energy is wasted by blowing it out the end of the barrel. The muzzle blast collides with the air mass and creates an ear splitting explosive noise, which can give away a soldier's position. Instead of harnessing the muzzle-blast energy and putting it to work for military and law enforcement purposes, this energy is currently wasted.
Utilization of muzzle blast energy to propel a grenade was practiced beginning in World War I. At first, this required a blank cartridge so that a bullet would not impact and blow up the barrel. Later inventions utilized a “bullet trap” or cup which caught the bullet and transferred its momentum to the grenade.
The French developed the VB grenade, shortened from its full name the “Vivien et Bessiers” shoot-through grenade. This technology also required a special cup adapter enabling its function.