That's an interesting set up for the internals, thanks for posting the description & drawings. I think I'll get things to a stage where the piston is free to travel the length of the cylinder without binding & locking up before trying it with the one original spring. If its fairly smooth & power is adequate for 15 yd paper punching then all well & good but if not then a spring swap & some form of guide / sleeve might be required.

I'm sure you are right about that piece being the trigger bent, but it definitely looks like a lump. I'm intrigued by the design, on one hand it seems all about ease of manufacture, cost minimalisation & function. Yet I would have thought the two spring set up wouldn't have got off the drawing board, or testing based on the latter. It's no LP53.

Still can't work out how the piston is so tight, cylinders don't shrink & steel pistons don't grow......

Unless I can sort out the barrel wobble on this one it might not be capable of anything where the word accuracy is used to describe its capabilities........