Consists of a steel auxiliary device with a removing breech plug with a spring loaded pin on the side which matches a hole near the head when in place. The front face has a rim firing pin for the .22 LR ammunition used. Smooth bored to the muzzle and was used for non-automatic practice on miniature ranges. (Fleming p. 143)

Base with the spring loaded breech plug removed.   

Spring loaded breech plug shown at 200% scale.

   .22LR cartridges used