As per Dan request, I am attaching a couple of pictures from My friend José's gun.
He has been a pneumatic guy for life but wanted to try band guns, so he took a Riffe, dimantled it and pretty much copied it with hand tools. The only thing he didn't do was the guide. Al the rest is done by hand with file, saw and drill. Even the mechanism, which he copied from Riffe and accepts both Euro and American shafts. EVERYTHING was hand made!
Of course he could do something better looking, but is his first prototipe and it works!
Enjoy...