sensor 16 in fig4 one end of the feeder tube 2 adjoins the inlet to the projectile chamber 11 of the weapon 1 a light barrier 17 in the sensor 16 intersects the feeder tube 2 in a direction perpendicular to the plane of the drawing during the resting phase depicted in fig4 a the feeder tube 2 is completely filled with balls 14 and the frontmost ball 141 is situated at the entrance to the projectile chamber 11 of the weapon 1 the entrance to the projectile chamber 11 is closed and all the balls are at rest within the feeder tube 2 the series of balls 14 contained in the feeder tube 2 is acted on by the spring force transmitted via the feeder 8 the light barrier 17 is interrupted by the ball 141 and the sensor 16 reports the presence of a ball after a shot is fired by the weapon 1 the inlet to the projectile chamber 1 opens up and the frontmost ball 141 driven by the force of the spring moves into the projectile chamber 11 once the ball 141 has partially entered the projectile chamber 11 in the status as depicted in fig4 b the light.