Once it opens it will drain all the pressure in the firing and reserve chambers until it is equal to the force of the spring.

Why even have the black sleeve, why not just use a machined brass nipple?

jsr instead of trying to guess at the proper tightness. Why not use a feeler guage to measure between the detent cap and cartridge? It might take a while but if you change the amount the cap is screwed in by a small amount then test. You should be able to maintain a pretty good firing probability ...

How did you cut the asa threads for the CO2 tank? Or did you buy some sort of adaptor?

I have a feeling a leak, large pilot volume and the some what restrictive pilot are the culprits. Here is a link to how to apply PTFE tape

Your pilot volume is probably hurting performance as well. Why not place the blowgun where the ballvalve is and use a trigger linkage, and then put the ballvalve where the hosebarb is.

also looks like the barrel wobble could have had an effect. also it looks like the sabot never discards, or it does so very late

You don't think those brass fitting are at risk without the tank being supported elsewhere? For safety maybe you should have the tank also supported by the barrel, better safe than sorry especially with high pressure.

I also know that there are piston valve hybrids - if they can handle then why wouldn't this thing ?

It wouldn't be difficult to build a bolt action rifle around this system (and hopefully a true semiauto )

I have yet to see a piston valve hybrid that was fired as rapidly as bolt action or semi ...

How is the sealing face attached, if it is screwed it could be leaking through the threads. Listen to the above advice as well.

Where did you get the nylon spacers?

"this is for most "digital" eye boards; analog adjustable boards will boost the detection range, however Morlock boards use a digital eye signal" (from zdspb site)

AFAIK the eyes operate only in conjuntion with the board of the gun, but I'm not entirely sure what your asking.

My opinion is that someone on this website could probably build a better and more powerful APG (airsoft pneumatic gun) and possibly even a higher rate of fire. I am wondering why they went through all that trouble when they could have made a vortex block or something.

efficiency, reliability and ...

I think the porting idea has some merit. Take the last foot or so of the barrel and see if it helps, if not it can always be used to make an integral suppressor . Also if it doesn't work on its own we could add in friction as you suggested.