[mcguyver]

Compression may in fact not be good. A slow speed test with your finger does not always replicate good high-speed flaring of the piston head o-ring against the cylinder wall. I've found that when using full cylinders, use a ported piston head. If the CYMA head is a ported head, try a different o-ring or replace the head.

You will also be able to tell if your comrression is good by dry-firing the fully assembled gun and seeing how much air comes down the barrel (use a tissue paper at the muzzle) and see if any air is leaking out the feed nozzle at the hop-up.