7.62x51 NATO GRENADE LAUNCHING BLANK

Think of a grenade launching blank as a "Hail Mary" throw in football.  Powerful, with a long slow follow through made for a moderate to longer distances.. 

A Military training blank for weapons is more like a volleyball serve. A quick light slap to get the ball moving a short distance. It only needs enough power to make the blank adapter at the end of the barrel cycle the weapon.