Originally Posted by Kmaddock
It looks very tight between the cylinder and the ricasso for a round to fit into the chamber. The small hold in the handle I presume is for when cartridges blow out.
Why the grove is in the cylinder is confusing as well.
One thing to consider is that in my youth when making .22 guns is that you can set off a rim fire on crushing it from the front of the rim. This might explain the detonation method.
The slide bit with the bar protruding might be the firing pin that the hammer propels forward or Maybe this was cocked back, held by the hammer device and then flew forward to strike the rim of the round
I will try and take a picture f the picture and make some sketch.