Any idea why? Quality problems?
Somebody should make these... 
It had it's issues too, basically, it was a thumb advanced rotary mag that
dropped a pellet into the trough ahead of the bolt probe but behind the breech opening. So...think of a bomber aircraft looking for the sweet spot to drop it's bomb. Wind? Elevation? Angle/speed? Bomb (pellet) shape?
All of these factors played into it's effectiveness, not to mention scope clearance. Good concept but... too many variables within the guns and shooters it was applied to IMO.