Kalibrgun Cricket problem

[MikeGB]

Hi,
I bought a used Kalibrgun Cricket recently, thought it was cheap and it seemed to shoot OK but I have found out why now, it shows some big spreads in velocity.
Smallest spread I have recorded over one magazine was 30 fps, worst was over 100 fps.
I thought at first it was a regulator problem and when I pulled it out I found a 'huma' reg in there, not a standard one.
I sent the huma for testing and service but no change in the velocity spread when the reg came back so wondered if anyone might have any ideas about what could be causing this.
No sign of any leaks, gun hold pressure well and have let cylinder pressure fall below regulator pressure but no difference.

[mr007s]

Hi Mike, I have dealt with Charlie at Georgia Air on a couple of occasions. He knows the ins and outs on your gun .He will be the go to man to help you out. Call or email him, he should be able to get you fixed up.

[MikeGB]

Will give them a try, thanks.

[mcoulter]

I just picked up a cricket .25 bullpup and I am experiencing the EXACT same behavior.  My changes in velocity are definitely related to inconsistent hammer spring strikes.  The gun has an aftermarket power adjuster which seemingly is contributing to this behavior.  Here's a pic.  How does your gun cock?  How does it feel when you get the low-velocity shots?

I have another adjuster on the way.  One that does not have the extra weight/spring guide.  It's the piece that looks like a nail.   





This is the one I have and will be taking out:

https://www.ebay.co.uk/itm/153501775178?ul_noapp=true

[MikeGB]

Hi, Problem turned out to just be the hammer spring in my case, after wasting money on regulators and stuff. The UK importer cuts the springs to limit power and they do a pretty bad job, I got a bag of cheap springs from China just to experiment with and am still using one, can't remember how many turns they are but 50 mm x 9 mm x 1.4 mm wire dia. The ends have to be ground flat and square, I also polished the ends and the sides, in and out.
I have tried the adjuster you have and one similar with a fixed spring guide and I prefer the one you currently have, seems more consistent to me.

[mcoulter]

Excellent!  I'm glad it worked out for you Mike!  I'm hoping for a similar outcome with my cricket :-)

[anti-squirrel]

Just following along here for the reference material.

MikeGB- how is the Cricket throwing lead now?  Hopefully the spread of velocity has tightened up significantly.

Matt, be sure to follow up with your findings as well.  Crickets generally seem to be rock-solid; also nice knowing a vendor with a solid rep is only a few state away.

[mcoulter]

I received the new hammer spring adjuster today.  It feels really good in the one magazine I had time to shoot.  I gave it a total guess at how much to turn it in, but I came out with a consistent 49 fpe with the air arms 25.4 grain pellets (935 fps).  I can't wait to see how it performs over longer strings!

[only1harry]

Glad you figured out it was the spring.  Moving this to the PCP gate where it belongs, and so that others can see the information or resolution, or search for it there in the event they have the same issue.

Harry

[MikeGB]

Spread is down to less than 10 fps usually at all velocities, from over 100 fps sometimes and accuracy has improved, could never get a tight group before, not down to putting them all through one hole now but good enough for me.

[anti-squirrel]

Spread is down to less than 10 fps usually at all velocities, from over 100 fps sometimes and accuracy has improved, could never get a tight group before, not down to putting them all through one hole now but good enough for me.

That's a significant improvement, Mike- glad to hear that things are working much better.

[mcoulter]

Here's the 1st full (60-shot) string I did after installing the new hammer spring adjuster.  The wild swings that I had seen from shot to shot are gone too  :-)

https://photos.app.goo.gl/aZVCGJQYiqqULj6J6




I then did some further hammer spring testing and found that with Air Arms 25.4 grain pellets it maxed out at 995 fps (just under 56 fpe).  I backed off two turns on the hammer spring and it's now shooting them at 970 fps (53 fpe).  At this setting it's shooting JSB 34 grain MKII pellets at 890 (just under 60 fpe).  I'm running low on pellets so I'll have to wait until my pellet order arrives on Monday to do some longer shot strings and accuracy testing.  But so far I'm a very happy camper  :-)

I'd also be willing to bet that at the higher HS setting that the surge at the end of the graph will be greatly reduced...

[Motorhead]

Reg setting is definitely NOT correct for the hammer energy being used. Thus the Spike in velocity as you come off the reg.

[mcoulter]

Reg setting is definitely NOT correct for the hammer energy being used. Thus the Spike in velocity as you come off the reg.

Yes sir.  I am hopeful that my increased HS tension will bring the base velocity up to where the spike was in my graph.  I just ran out of pellets (and daylight) to test.  My PA pellet order arrives on Monday and I'm off this week    It is kind of fun sorting through what the last couple of owners did...  :-0

It looks like the velocity starts to spike around 1950 psi / 135 bar, so can I take that as the estimated regulator pressure?

[Motorhead]

What it tells you is Reg pressure is set TOO HIGH because the gun makes more power at a lower pressure.
reducing set point will allow less hammer strike energy because valve will open easier.

[anti-squirrel]

My exposure to threads involving higher end PCP like the KalibrGun Cricket is educating me- thanks for the insight, Scott

Matt- be sure to keep posting wit your results.  Kalibr is on the very short list of possible next purchases

[mcoulter]

What it tells you is Reg pressure is set TOO HIGH because the gun makes more power at a lower pressure.
reducing set point will allow less hammer strike energy because valve will open easier.

Thanks Scott! 

And yes I'll definitely share results as I go along.  Fwiw, even though I'm having to sort out somethings with this gun, I'm really liking it! 

[mackeral5]

It is interesting that over the years I've read many posts relating to hammer springs presenting challenges in Crickets.  I believe I've even seen reference to removing it from the gun during extended periods of storage. 

So far I haven't experienced this phenomena with any of my guns (QB variants, Edgun, WAR, SPA)---is this something unique to the Cricket's design?   

[mcoulter]

One more post on this thread and then I'll start a fresh one (sorry to the OP for hijacking it)  :-)

Keeping the same settings as the earlier string, I decided to shoot some JSB MKII 34 grain pellets.  Here are the results on a 215 bar fill shot down to about 100 bar:



After shooting this I cracked open the gun to inspect the regulator.  I'll pause here and start a new thread on that chapter

More >> https://www.gatewaytoairguns.org/GTA/index.php?topic=166657

[tefloncoated]

Hi, Problem turned out to just be the hammer spring in my case, after wasting money on regulators and stuff. The UK importer cuts the springs to limit power and they do a pretty bad job, I got a bag of cheap springs from China just to experiment with and am still using one, can't remember how many turns they are but 50 mm x 9 mm x 1.4 mm wire dia. The ends have to be ground flat and square, I also polished the ends and the sides, in and out.
I have tried the adjuster you have and one similar with a fixed spring guide and I prefer the one you currently have, seems more consistent to me.

In case anyone in the future is looking for the 25 cal Hammer Spring specs, here are the official ones that came directly from Kalibrgun (in mm):

Dimensions of the spring:

1,25 -power of the spring wire

9,25- diameter of the spring

62 – length of the spring

17,8 - number of coils