Airsoft Micro HPA engine

Airsoft HPA engine using the operating principle from Kuba T-1000. This is the mechanical comments only. When fed a pulse of air it will extend the nozzle, then release a burst of pressure.
Apologies for the mix of metric and imperial measurements.
Non printed components:
1 x #5 O-ring (5/16 OD x 3/16 ID)
2 x #7 O-ring (1/2 OD x 3/8 ID)
3 x M3-40 bolt (needs to have a flat head)
3 x M3 nut
1 x metal tube (5/8 OD x 1/2 ID x 30mm)
6mm pneumatic tubing (4mm ID)
Optional: 3/16 in x 14mm Steel pin

I created this while trying to miniaturize the Kuba T-1000 mechanism. This was the smallest size I was able to shrink the parts. I never could get much power out of it, 0.5J was the highest energy I got. If anyone can work out how to get more power I would love to know how.