I made the rather optimistic purchase of a very cheap, tatty, incomplete Schimel GP22 for spares a few months ago.
Close inspection of the distortion of the metal in broken foresight area of the barrel shroud confirms a previous owner discovered the barrel housing to be siezed in the frame by twisting with the foresight and snapping it off
I'm now in the process of machining out the barrel shroud (having first determined it's internal dimensions) prior to making a new one, plus a replacement backstrap (original present but broken) and hopefully a 12g compatible CO2 housing/piercer assembly (the missing bit!).

- Nick