Cricket tune questions
Ordered compact cricket from WWAG…Charlie F called me prior to shipping and asked me how I liked my gun to shoot. He said it’s shooting ~800 fps. I told him I want it shooting around 880, didn’t care too much for shot counts. So gun arrived and I’m indeed shooting around that range…using H&N Baracudas! (He tested them using JSP 18grn). So that was a nice surprise.
However, I am not satisfy with the chrony numbers I’m getting. I filled to 3000psi and shot 14 shots and got the following…
880, 879, 874, 876, 877, 877, 874, 880, 880, 878, 877, 875, 876, 875
standard deviation = 1.9, average 877 fps
Filled to 3000psi and shot another 14 shots:
874, 879, 874, 882, 883, 884, 886, 880, 886, 877, 880, 884, 879, 884
standard deviation = 4.2, average 880 fps
Fill to 3000psi and shot another 14 shots:
883, 898, 903, 894, 899, 897, 900, 889, 885, 886, 887, 883, 886, 884
standard deviation = 7.1, average 890 fps
———————————————————————————-
So what the hell is going on here? What’s up with the inconsistency? IS THIS ACCEPTABLE? I don’t like it! I thought the cricket regulator is supposed to be better than this.
What is an acceptable standard deviation? Do I have to mess with my regulator? Is the regulator set too high or too low? Could someone please help? I’m going nuts here :banghead:
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Viewing 15 replies - 1 through 15 (of 15 total)
Thank you my friend but some questions do arise for an inexperienced poor man as I am.
Is there one bell curve for all possible VST/HST settings? Or multiple curves exist, each VST/HST individual setting corresponds to one specific curve?
I will try to make this magic trip alone into the tuning abyssos if you could advise me how to obtain bell curve the right way. I mean how many bars should I pump the gun after I unseat reg, should I put light VST and mid-way HST and record speed and bar reading per shot? I haven’ set a clear view on the subject yet.
Regards,
George
I’ve noticed the same phenomena on another regulated gun that was very far from it’s optimal tune, with springs and reg pressure totally unbalanced. I think this will problem will disappear if you manage to get the gun in tune, I don’t think the problem is a leaking o-ring. Correct me if I’m wrong.
One way to find the optimal tune is to take out the reg, setup the HST and VST so the rifle shoots a little more than the desired speed at the peak at the bell curve. Note the pressure at the peak and set the reg to this pressure (you can measure reg pressure with the RAI). Lower HST slightly to get desired speed, keep VST. The gun should be very consistent and air efficient at this setting. If you want even better consistency but at the expense of a little air, you can leave HST as it was when shooting unregulated. The process is time consuming, but you get good results. If someone has an easier method, I’d like to hear it. 🙂
While closing to target speed I noticed a strange phenomenon,
gun is consistent if cocked and fired quickly (2-3 sec) shot after shot. When there’s some time between shots, let’s say 5-6 sec, then I notice significant drop of speed, 200 fps down!!! When I fire it quickly again, consistency is back.
Suspected leak and left gun rest overnight, next morning was still as I left it. Reg seems working fine. There’s a RAI installed and should provide plenty of regulated volume but something is not working as desired. Cricket is compact .22 with VST spring changed to lighter one with low tension, HST stock FAC spring halfway, reg set to 100 bar, 40 fpe but with the above strange problem.
Any idea will be appreciated,
regards,
Geoge
The relationship between HST, VST and reg pressure is, very simplified: HST balanced with reg pressure + VST. The VST + reg pressure works together against the hammer.
This is to keep same spot on unregulated bell curve which should mean same consistency.
In order to keep the same balance you should use softer valve spring tension (VST), not higher and/or higher HST. Most people leave the VST alone and only adjust with HST. Start with resetting the VST to 1 turn CW from initial tension, then try higher HST by 1/4 turn CW at a time. You can also try 1/4 turn softer VST.
Hello all,
after some good reading on the subject I’m trying to achieve a self/home-made tuning of my .22 Compact Cricket. A good quality pressure gauge and a Combro are my allies in this battle. Gauge fits on the drain-hole of the firung valve body.
Gun was chronoed 860 fps very consistent shooting 18.1 JSB out-of-the-box. Unknown reg pressure, suppose it was around 110bar. HST 1 turn CCW from full, that is one turn CCW after screw it all the way in, stock spring 56mm. Firing valve spring (stock spring also) was 1 turn CW after spring’s initial constrain by perforated aluminum disk compressor.
Wanted to go up to 880-890 so tried to set reg higher.
Current setup is; reg 122 bar, seems OK. HST 1 turn CCW from full, firing valve 3 turn CW after spring’s initial constrain. Shoots 16 grain 5.51 pellets as per
810,807,809,807,808,740,810,745,809,810,743,808,809,808
Forgot to mention that I also installed a RAI.
What is the influence of valve spring tension on this phenomenon? What am I missing? Obviously I don’t quite understand how to use higher pressure to propell the pellet efficiently. Thanks to Ernest, sniperlabyo, I did understand the influence of HST and how to obtain maximum speed by test, is there anything else that I should focus on?
Regards,
George
Your sample size is too small so your estimate of the SD with a confidence level of say 99% can have a significant error. The SD number can probably have an error of +-50% using a population of 14 so statistically there may not be any difference between the 7.26 and the 2.79. They are within the sample error.
Also, you need a full string to determine of the regulator is properly adjusted since some behaviors only show up near the beginning or end of the shot string before it falls off of the regulator.
You need a full string. What can it do – maybe 30 shots?
800, 800, 800, 800, 800, 800, 800, 814, 814, 814, 814, 814, 814, 814
sd = 7.26
800, 807, 808, 807, 808, 807, 808, 807, 808, 807, 808, 807, 808, 814
sd = 2.79
Obviously, the second one is better….
[quote=”SECoda”]
btw- 14 fps max spread isn’t bad.
[quote=”tbear”]
Well that depends, that’s why I’m looking the at standard deviation. For example:
800, 800, 800, 800, 800, 800, 800, 814, 814, 814, 814, 814, 814, 814
sd = 7.26
800, 807, 808, 807, 808, 807, 808, 807, 808, 807, 808, 807, 808, 814
sd = 2.79
Obviously, the second one is better….
Don’t turn the HST 1/2 turn. That is way to much. One issue is statistical. Your calculating a SD on too few shots so there is a lot of variation. Do a full string and post it from 200-220 bar down to falling off of regulator.
btw- 14 fps max spread isn’t bad.
However, I am not satisfy with the chrony numbers I’m getting. I filled to 3000psi and shot 14 shots and got the following…
880, 879, 874, 876, 877, 877, 874, 880, 880, 878, 877, 875, 876, 875
standard deviation = 1.9, average 877 fps
Filled to 3000psi and shot another 14 shots:
874, 879, 874, 882, 883, 884, 886, 880, 886, 877, 880, 884, 879, 884
standard deviation = 4.2, average 880 fps
Fill to 3000psi and shot another 14 shots:
883, 898, 903, 894, 899, 897, 900, 889, 885, 886, 887, 883, 886, 884
standard deviation = 7.1, average 890 fps
———————————————————————————-
So what the hell is going on here? What’s up with the inconsistency? IS THIS ACCEPTABLE? I don’t like it! I thought the cricket regulator is supposed to be better than this.
What is an acceptable standard deviation? Do I have to mess with my regulator? Is the regulator set too high or too low? Could someone please help? I’m going nuts here :banghead:
an important issue is the hammer spring tension, the spring must to have some tension, too loose down consistency
then tried to give some tension, turn CW half turn, an try again
Try to make all string from 200 -110 bar or what you prefers. There is better see behavior of regulator.
I’ve already gone through two tins so after 100 more shots I’ll give you guys an update…
Gun is new and all parts in the gun are new regulator include… Be patience and shooting some time without chrony (500 shots) and after all parts settled correctly check whole string with chrony 200 bar to 110bar and you will see deviation and shot count as well.
Give it some time & shoot it. The reg does require some break in shooting to settle in for best consistency.
Im no expert, but that looks a hell of a lot better then my edgun
Viewing 15 replies - 1 through 15 (of 15 total)
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The “bell curve” is the plotted shot sting you get when shooting a fill from an unregulated PCP through the chronograph. Y axis is fps and X axis is number of shots. At the highest fps you have the “peak”, the top of the bell curve, and here is the point where your rifle runs the most consistent. That is why you take note of the pressure in the reservoir at this point and set regulator to this pressure, so that the valve will always work against the pressure where it outputs the most consistent power, the optimal pressure.
The characteristics of the bell curve will change depending on your settings on HST and VST. Also things like hammer weight, transfer port size, ammo used etc affect the bell curve, so best to keep as many constants as possible and change only one thing at a time.
My method means finding a good unregulated bell curve first, playing with HST and VST to get a flat bell curve at your desired power setting. (I have also sleeved the transfer port down, but this is only good for lower power settings 7-12 FPE or so.) Then set the regulator to the pressure you get at the top of the bell curve.
There is tons to read about this, do some research using google. I’m only a novice…