Cricket plenum spacer and "Regulated cc volume"?

Hey i am from iraq how can i get cricket plenum

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Hi @Hussseinyousff I bought the gun used and it came with it so I can only suggest starting with contacting Georgia Airguns. He has been working on these guns as long as anyone!

https://georgiaairguns.net/contact-us

V = πr2h

Take your measurements in millimeters and move decimal one place to the left (or divide by 10) which converts them to centimeters. Measure the I.D. of the tube for the diameter and divide by 2 to get radius.

If you don’t want to manually calculate the formula then use the below link to this cylinder volume calculator. Just plug the centimeter measurements in. 


https://www.mathopenref.com/cylindervolume.html

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Thanks@

I also need to determine the original plenum / air volume size for the purposes of the spreadsheet. I will try to calculate that next time I have the gun open! 

Thank you Centercut! I had not considered how the reg would have reduced the available air tube volume.

OK, just circling back on this before I forget...

To guestimate my available air volume in the tube... 

1) My internal OEM plenum spacer is 2.5 cm long and the area inside the tube where it sits has a radius of 1.5 cm = 17.67 CCs of space consumed. So 332.33 CCs are left of my stated 350 air volume.

2) I'm estimating the body of my regulator is a 2 cm with the same radius so that's 14.13 CCs of space consumed. I need to take a way a bit more volume for the slim part of the regulator so let's round up to 20 CCs of space used. This brings my usable air cylinder volume down to 312.33 CCs.

Then my total plenum space guestimate...

1) @zx10wall originally helped me calculate that my plenum extension is 31.8 CCs 

2) The inner volume of the OEM spacer is 13.27 CCs (13.cm radius x 2.5 cm long)

3) Going from my pics it's really hard to come up with the volume inside the valve body. My best guess is maybe 15 CCs

Adding these up I get an estimate of 60 CCs for the plenum.

So using Sikes' efficiency calculator I get 1.44 avg FPE/cuin per shot

http://www.calc.sikes.us/1/index.php

psi start & end = 3118 / 1668
gun tank volume = 312
pellet wt = 25.4
60 shots
900 fps avg

Awesome! What's your reg setpoint at? Just remember when using the calculator if you fall off the reg pressure then total CC's used would include both reg and reservoir

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Howdy, I have the reg set at 120 and I shot down to 115 bar. Thanks, I had not considered that. I updated my TriggerTreat spreadsheet and it came up with an efficiency number of 1.39. Since that one asks for the reg pressure and reg cc, perhaps that takes this into account.

https://photos.app.goo.gl/bfG5AMjBVA3AoDmC8



I will say that this is probably the best the gun as sounded.

I’d recommend doing it and stopping your shots about 5 or 10 bar above your reg set pressure so you don’t complicate things too much. Very good efficiency. 

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Thanks, I will give that a try. Hopefully this weekend I'll have some trigger time

And for reference, here is the hammer spring test I did at the above reg settings (120 bar).



(updated the above graph with better y-axis range)

Good news / bad news regarding my calculations above.

The good news is that my plenum estimate was really close. I decided to email Kalibrgun and just ask them about it and the actual air cylinder volume. They said the .25 caliber has 26cc plenum (17cc on other calibers) and the advertised 350cc air tube capacity IS the real air tube capacity. So my plenum with the extension is 57.8 cc (i'll round up to 58 cc). I also asked about the standard regulator setting. They also said the gun ships with the reg set to 125 bar. The only question they were not able to answer for me was how the firing valve preload was set from the factory. Changing the air cylinder volume back to 350 cc drops my efficiency to 1.27:

I have not shot the cricket much since finding a great deal on a .22 cal diana 54. I really do need to have both a PCP and a springer in my collection.

Anywho, I did another hammer spring test with JSB MKI pellets. Six turns on the HS felt just about right. I did not have time to shoot a full string with these pellets to check for efficiency. 



So with the JSB MKI (it's favorite food) 6HS / 840 fps = 53 fpe @ a regulator setting of 120 bar. Now given the plenum extension and my estimated volume of 58cc, would you cricket gurus think it's worth playing at any reg settings higher than 120? The accuracy is definite there right now so I am trying to resist the urge to test just for the sake of testing ;-)

After doing the HS testing, I shot these 7 shots at 70 yards. The one outside the group was me not getting my holdover right. The sticker above the group is 1/2 inch.

Gotta ask how your gun is performing now. I have not heard of many crickets being shot at 140 bar much less 150 bar.

My plenum extension is threaded and unscrew as you would expect. The real challenge is plucking the regulator out. 

My gun was used and had a huma reg. Not sure if the stock cricket reg has the same female threads for a long m4 (?) Screw to pull it out with...