Cricket velocity spread problem
Hi, I bought a used Kalibrgun Cricket recently and am having a problem with erratic muzzle speeds, best I have had from 14 shots was between 552 and 582 fps but have seen well over 100 fps spread on some series of shots, sometimes going into FAC territory.
My first thought was regulator so got a Lane Mk9 but it has not made any difference so wondered if anyone could suggest where to start looking for the cause of this.
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How is it going?
I haven’t tried letting the cylinder get down that low yet, still experimenting with rotating barrel, friend says the transfer port is only about 1.0 mm dia in his 12 ft/lb FX Dominator, it has a brass restrictor in, leaves about a 4.0 mm dia hole if it is removed, wondering if I could do something like that between the air cylinder and barrel.
Also read about starting full in then backing the hammer spring off to see if there is a ‘sweet-spot’ power increase at any point and been trying that at the same time as barrel rotation.
I have had most of it dismantled and not found anything that doesn’t look like it belongs there, not sure if the main valve is standard.
I am finding it very slow to fill after I changed the O rings, backed the screw in the fill valve off a little, twice but it’s not making any difference.
So what is the power at 80bar left in the cylinder with your current hammer spring, if your hammer is shortened or weaker wire power will trend up to impressing numbers if you are not careful setting up the TP.
Also I read somewhere that some shops filled the plenum on some guns with some delrim bits in an attempt to reduce volume/power but failed miserably so I would check that making sure your valve and the plenum is normal, then adjust the TP.
If your reg is set that high 130 you have to clip the transferport a lot to even it out. The FPS will depend a lot on cylinder pressure regulated or not. Choke it down. Usually helps
It would seem to be the hammer spring that is the cause of most of my problems, the 1.2 mm wire size one was an improvement, then tried a 50 x 9 x 1.4, paid a lot of attention to squaring the ends and polishing it, plus how it was seating in the hammer and adjuster and am down to single figure fps spreads most of the time now.
Think it is just some fine tuning needed to match regulator settings and stuff and will try turning the barrel as it is border-line for legal here with the adjuster fully out.
Many thanks for everyone’s ideas and suggestions.
I’m still working through a lot of the suggestions, changes to the hammer spring seem to give changes more than other things, I have had it running at 900+ fps and only showing a 20 fps spread on some shot strings but as soon as I turn it down it all goes away.
I tried a 40 mm hammer spring of 1.0 mm dia wire and even with the main valve spring retainer only in half a turn and the adjuster full-in the hammer still wouldn’t open the main valve much. Found some more info on hammer springs about how the ends are important as it can alter position between shots so altering how the hammer hits, am currently getting better results with a 50 mm spring, 1.2 mm wire with ends ground square and polished. The original spring it had in really looked like it had been butchered and I am told it is the UK importer that leaves them like that.
Have also had a suggestion of putting a small plastic sleeve round the hammer spring as it was thought it could catch on things if the spring distorted at all.
Will try turning the barrel etc., thanks for the suggestions.
Man you have to turn the barrel so it clips the flow path, that way you can add more hammer spring tension. While you keep it around 575fps.
That way you can keep the high reg setting.
Don’t lower the reg too much that would make the gun inefficient and loud. Instead try what I suggested.
120-130 is high I would go to 90 as you will not have dead air just sitting in the cylinder what you never shoot. But don’t go too low as it will hammer bounce and waste air without making power.
Setup the TP and hst at low fill not with full cylinder. Only if you are happy then refill and verify fps with full cylinder. Will take a few turns but can be done.
Watch out for unbalanced effects as such: different power at or under the reg setting versus full cylinder. A properly setup gun has low extreme spread over the wide fill range and at the same time low shot to shot variation.
Will give the settings a try.
Posted questions on some UK forums but haven’t got anything useful off them, several suggestions of sending it to the UK importer but I have found them very vague or unhelpful when I have tried contacting them.
Not sure if I am on the right track but tried sealing the hammer area and under the trigger mechanism opening in kitchen film and put the tissue under the trigger rod and it is still moving a bit with the 16 x 2 O rings on the air cylinder.
I’m not a big fan of videos for technical stuff, I like something that I can to refer back to particular sections easily, I have downloaded a lot of the Lane documents since I got one of their regs and have done the tests in the ‘mini service guide’ a number of times and the 45 second test curves are improving but still a bit uneven, they did offer to take it back for testing but the Huma reg is producing similar results after it was tested so thought it probably wasn’t the regulator.
Also Lane is a great resource for regulator theory.
You need to do a full shot string and study its curve ……..
I’d go with the 85 bar reg settings …….
Play around with the Valve and Hammer spring tension to achieve a balance of the 2.
Try setting valve spring tension to 3-4 turns CW too.
I’m not usually into 12 f/lbs tuning so my knowledge is rather limited.
I’d check into some UK forum if u haven’t already ……..
……. also the tissue test u did on the underside could have come from the turbulence caused by the hammer making it’s way onto striking the valve ?
~ Greg
That’s interesting, thanks for the info.
I am still waiting for a selection of O rings to arrive to, hopefully cure the leak from the cylinder end, I got some 16 x 2 but they did not stop it entirely.
Bottom spring is 36.25mm long wire thickness is 1.05mm and spring ID 6.05mm it and the adjustable adjuster gives me a wide range of fps. No idea what the regulator is adjust to. But it shooting almost 13 ft.lbs. with 10.3 pellets.
My cricket is a standard .177 I ended up putting in a shorter spring to bring the fps down.
And managed to achieve a free flight hammer in the process. Top spring in the pic was what was in the gun the bottom is the replacement.
The lane was, and still is, set at 130 bar. When I got the huma back from service the test document said it was set at 85 bar but I have tried turning it up since and think it is on 110 bar now, didn’t take note of what it was when I sent it.
I have been doing some more tissue tests with the stock removed and if I turn it upside down with the tissue over the air tube end there is a little movement of the tissue when fired.
So I am just about to take it all apart again and try some different size O rings in there and think I will put the Lane reg back in.
I got some other springs and put one in same diameter and wire thickness but 50 mm long and the Cricket went straight to 900+ fps ( surprised how quiet it was ) so it seems it is not possible to turn the velocity down much using a full size hammer spring and the standard retainer, do the adjustable ones that are available allow them to be turned down to the 5-600 fps range.
Was still getting a 70 fps spread of velocity over 14 shots with that spring in it.
Is the Lane Mk9 setup for 12 ft/lb when u bought it ?
Whats your reg set at ?
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I think it is about sorted, thanks for asking.
The velocity spread problem is fixed, still experimenting with hammer springs and port size from air cylinder to barrel a bit but am a lot happier with it now.