Tuning Cobra valve tech built into raw valve

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Well I blew the first poppet I made apart dry fired at about 50 bar and I think the outside of the poppet bottomed out on the outside of the chamber and that was it for that lesson learned so I made another poppet with a longer spring guide so if it were to bottom out again it would do it on the inside of the chamber so the stem doesn't break apart the poppet again made this one to .325 and took the front of the poppet down to about .235 and got the oring to fit good I the 1/4 inch sized chamber which I took and lengthened the depth of the chamber because of the slightly longer poppet I didn't lap this one in yet just threw it together it has a 30 degree sealing angle and pretty much sealed all the way up I have under a 150 bar left in my tank apparently my bottle oring decided to let loose now to so I lost a bunch of air before I realized what was going on I put in as much air that would go after changing the bottle oring about 125 bar or so and I have a ever so slight leak yet at the poppet tried 2 shots and got 672 and 676 which were both off the reg since it is set at 150 I'll probably need more tension on ssg and give it another go after I lap in the poppet and fill my small 90 cu in bottle back up so I can try it above the 150 bar setting may need to shorten the poppet spring guide or just open up the vent holes poppet has about 3/16 of travel before it bottoms out on the inside and vent holes are at only .050 total between the 2 of them so I should have a working cobra valve tomorrow after lapping it in power adjustment will take some tweeking though it is sipping air at just under 700 fps though lol
 
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I don't think that any more shot count can be squeezed out of it.

However I shall check the shot count later.

There is a reason for which I cannot be sure about maximum shot count. In fact I have to use 25 grain and 34 grain both kind of pellets without changing the reg pressure. 

So I am not going to tune it for maximum efficiency for the time being.

Later I might tune it for 34 grain only
 
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Lapped in the valve it seal once I got over a 150 bar tried 12 shots on 3300 psi fill I got 835 low and a high of 846 but I don't know what my ssg gap is set at yet and that was with out the power plenum I will install the power plenum now a see where I'm at for speed and adjust my ssg tension and gap from there and see what I get so for It is looking good 
 
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Well I'm done testing for a bit the huma reg took off the first 2 threads on my raw bottle valve I'll be going back to the raw regulator and getting a new bottle valve which sucks bottle went in like normal shot the gun Down to 150 bar on gauge turned it about a turn and fired again turned it another turn and fired was coming off like normal the the last 2 threads bottle got stuck had to use a wrench to get off the reg found the first 2 threads gone wtf I'll be contacting huma and see what they say never had problem before mean while I'll be looking for a bottle valve to fit it 
 
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Bleed holes .. .040 to @ .070" Start small and if power really takes a hit open it up. It will be a Try and see result type tweaking of said vent size.
Click to expand...

I had an idea a while back after reading the GTA thread on making the bleed holes adjustable.

Instead of using a single hole with a fixed size, the idea that came to me was to use multiple smaller holes (maybe with a #80 drill), and then making an adjuster that exposes N number of holes depending on the setting (kind of like a kaleidoscope).

Have some ideas on how to make that work, but I'd probably want to draft something like that with CAD before attempting to wing it by hand.

Just an idea.
 
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In the rifles I’ve used a cobra set up . I use carburetor jets. They can be had on eBay for fairly cheap and you get a wide assortment. I found the volume to be tricker to get right. Between the stroke and the bore size I tend to go a small as possible with a maximum of .25” travel . One of the best features is the ability of the set up to self regulate in non regulated applications. 
 
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I was playing around with the idea of putting a needle valve like in a carb out the front and fit a oring on the inside where the needle valve goes in to seal it and thread the needle valve wouldn't take much adjustment to be fully open or fully closed I don't have the tooling for cutting internal orings in anything but peek or other plastics 
 
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Well I got a average of 880 19 fps spread 50 shots avg 58.5 fpe .93fpe / cuin had a 12 fps spread for 45 shots not to bad with a .020 gap on ssg 3550 fill .170 tp 61 gram hammer and am using a viton oring in the cobra chamber so I'll switch that out to 70 or 90 buna and may play with tp sizes yet to that's at 150 bar on the reg and only 92 shots on this huma reg so far looks like the cobra valve is working cut my spread pretty much in half just need to get shot count back up I may try a lower reg setting to to up the shot count using 34 gr mk2 even if they are at 850 it would be fine for me also lubed hammer with mobile one multi viscosity making some progress anyway
 
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Well I got a average of 880 19 fps spread 50 shots avg 58.5 fpe .93fpe / cuin had a 12 fps spread for 45 shots not to bad with a .020 gap on ssg 3550 fill .170 tp 61 gram hammer and am using a viton oring in the cobra chamber so I'll switch that out to 70 or 90 buna and may play with tp sizes yet to that's at 150 bar on the reg and only 92 shots on this huma reg so far looks like the cobra valve is working cut my spread pretty much in half just need to get shot count back up I may try a lower reg setting to to up the shot count using 34 gr mk2 even if they are at 850 it would be fine for me also lubed hammer with mobile one multi viscosity making some progress anyway
 
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Added another vent hole for a total of 3 and size of .064 changed out the viton oring to 70 buna didn't have a 90 and swapped out the tp to .150 filled it to 2500 psi while waiting for my large tank to fill and took 12 shots last shot was coming off the reg at 896 for a low and high shot of 906 10 fps spread was 6 till last shot used sikes calculator for efficiency it is now sitting at 1.04 fpe/cuin 61.4 fpe per shot 29 psi used per shot and a average of 902 so by adding another vent hole and changing transfer port to smaller .150 size from like .170. I used less air but gained in fpe which also should help my es as well 
 
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