.22 Cricket mini Carbine Power Tune

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Centercut

Centercut

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Jun 9, 2017
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I've been thinking about this since I bought the power plenum in July, and finally decided to try and "power tune" the .22 Cricket mini Carbine to shoot the JSB .22 RD Monsters at a good speed, preferably at 875 FPS if at all possible, while still retaining a minimum of 35 shots per fill to 250 bar. The gun is currently a 30 FPE gun, 55 shots on reg. per 250 bar fill, and I'd be going up to 42 to 43 FPE. What I want to get is "standard" .25 "JSB King" performance from a small, light, super accurate and easy to shoot gun like the Cricket mini. I had considered the Wildcat Compact in .25, but the FX really only shoots one pellet well and with the CZ hammer forged barrel, the Cricket will leave the door open to other "heavy" .22 caliber pellets. So, the overall plan is this:

1. Add additional "power plenum", purchased from Ernest a while ago on eBay. Not sure if I'll drill and tap for a reg. pressure gage yet.

2. Replace valve spring with longer, lighter spring and adjust as per Ernest's video.

3. Replace hammer spring with stronger spring. I have three different Cricket sized hammer springs that I can experiment with.

4. Replace the plastic HST adjuster with a metal one.

5. Port and polish the air inlet to the valve (small holes will be polished and holes chamfered, not enlarged much).

6. Enlarge valve port by enlarging it in an "oval" shape by 0.5mm on each side, and chamfer port edges.

7. Enlarge barrel port in the same manner as the valve port.

8. Add Huma reg. to replace the Cricket reg. I don't think the Huma is any better than the Cricket, but it is much easier to adjust, especially without a reg. tester. If I had a reg. tester I would use the Cricket reg. after polishing the Belleville washers as per Ernest's video. Without a reg. tester it would involve too much in and out to get it just right. With the Huma I can at least adjust per the label and be "close", since in my experience with other Huma regs. the label in bar has always been pretty close to reg. set pressure.

Finally, once assembled, and reg. set to 145 to 150 bar to start, tune the gun using reg. pressure and HST as discussed in numerous posts on this forum. From what I gather from Jimmy's .22 pup power tuned by Derek, the CZ barrel "should" be accurate with the RD Monsters. Yes, its 2 inches shorter than the pup, but other than that the same. Since Derek got around 885 FPS with his tune, I feel that I can get around 860, but my goal is 875, and still get a good number of shots (35) from a 250 bar fill.

We'll see how it goes. I have most of the parts now, but still need the Huma to start the tune. More to follow...

Mike
 
@intenseaty22, Christian, yes, I "buckled." Who do you think bought that Cricket mini that was on AGN Classifieds a week or two ago? I wasn't going to do it with my laser beam mini. LOL. Funny thing, the serial number on this one is only 7 higher than my "old" mini, probably made on the same day, or at least the same week. And I have to admit, the Charlie Freer trigger tune is better than my current mini, totally about a perfect trigger as I've felt, as good as my RAW or FWB 601. So, it'll either be a success, or I'll put it back to stock and sell it to some lucky shooter... Once (if) the project is a success, and it gets 35 shots per fill, and shoots ACCURATELY at 42 to 43 FPE, Nick (@socaloldman) gets first dibs on this one., since he wants exactly what I described in the first paragraph of my initial post - and he's a great shot, so ground squirrels stand by! ;)
 
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Interesting build, asking a lot for a 15.35" barrel though...I am uncertain you'll obtain your targeted 875 FPS unless you run REALLY large ports or 160 bar reg pressure. I don't know what your final port size will be with .5mm enlargement but I advise going as close to 85%-90% bore porting as possible to obtain your desired FPE/FPS...JMO! I could be wrong...



That 2.2" inches of barrel might not seem like much but...from my calculations its a difference of nearly 50 FPS. Barrel lengths have diminishing returns but under 20" barrel length any additional barrel length is a HUGE improvement. 2.2" is 15% more length, even though the 2.2" is at the end of the 'pellets stroke' so to speak, its still considerable due to your barrel being under 20". 



Going from a 1" barrel to a 2" barrel is only a 1" increase but it increases length 100% and increases FPS by 50%, but as you work your way down the barrel with more length the pressure is dropping and additional length has much less effect, hence the diminishing returns. Which is why 15% more barrel length will only give you approximately 5-6% more FPS. YMMV as these are all approximations, but I have a feeling you will be shy a few FPS! 




 
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@ackuric, Not sure I understand what "85-90% bore porting" is? Please explain? Thanks. I'm looking at about a 1mm increase (0.5mm x 2) in valve port, and then matching that with the barrel port. Larger ports don't make much sense, since the barrel port is the limiting factor, and can only be so big due to the .22 caliber diameter. So making a huge valve port doesn't do much if the barrel port isn't a similar size...

I'm thinking 150 bar reg. pressure, but don't want to go higher than 155 or 160. Like I said, 860 FPS would make me happy, and I could live with 845 to 850. After all, Ted won EBR a couple years ago shooting at 830 FPS.
 
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@ackuric, Not sure I understand what "85-90% bore porting" is? Please explain? Thanks. I'm looking at about a 1mm increase (0.5mm x 2) in valve port, and then matching that with the barrel port. Larger ports don't make much sense, since the barrel port is the limiting factor, and can only be so big due to the .22 caliber diameter. So making a huge valve port doesn't do much if the barrel port isn't a similar size...

I'm thinking 150 bar reg. pressure, but don't want to go higher than 155 or 160. Like I said, 860 FPS would make me happy, and I could live with 845 to 850. After all, Ted won EBR a couple years ago shooting at 830 FPS.
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85-90% bore porting means whatever your bore is * .85-.9 so a .22 cal would be ideally ported to .187 - 198" to achieve the FPS you desire with that barrel length and regulated pressure assuming you have enough regulated volume. Of course this requires OBLONG barrel porting to accommodate the size as to not cause damage to the pellet upon loading. For example my .25 cal is ported .212 x .239 = .225". My valve is then ported the same @ around .2275".

For a .22 cal oblong port I would go to the likes of .176" (wide) * .2" - .22" long. That would give you between .188" and .198" porting which is between 85-90%. You need your throat to flow enough after subtracting the area taken by the valve stem so these types of valve modifications can require a bit of work. Again that is JMO and an option for you if you find your expectations not met when you perform the work you already have lined out. Its either that or UP the regulator pressure to 160+ IMO.

What will your final port diameter be after you open it 1mm? I can give you a ROUGH idea of what you can expect based on that information. If you have your regulated prechamber volume that makes the calculation even more accurate. If 850~ will make you happy you will have better luck hitting that then 875 IMO with your current conditions. But its not good to tune at the plateau, which that would be for you...you want to tune 3-5% FPS below plateau for efficiency and for when you drop off regulation, so there is a small bell curve which increases shot count..So keep that in mind! IMO
 
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Thanks! Great explanation. +1 to you. I definitely want to keep the reg pressure as low as possible to meet my objective. And yes, not at the plateau but just below that at the top of the "knee". That's how I have tuned my other guns successfully, but this step of opening up the ports is a first. I may just have a machinist friend do it to my specs. The regulated prechamber volume will be large, as I am adding in the power plenum. So standard 30mm tube volume and adding in about an inch, or slightly more same diameter. Pretty much doubling the current reg volume. 
 
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Centercut, all sounds great and I will be very interested to see your results. You have a port you’ve not yet addressed, the porting through the action; valve-> action-> barrel. 

By the way, when I port the firing valve, I address the material that creates a 90° flow path. I make a more “flow friendly” path by removing that corner and also enlarge the path as much as veasible. 
 
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Thanks both of you. Yes, I also assumed action porting, wouldn’t do much good to do the barrel and valve without that. Weakest link and all. When I said enlarge, polish and chamfer I meant rounding out any 90 degree air flow paths as much as possible. 

I’ve always just backed off 10 to 15 FPS from the plateau and had great success and efficiency. My .30 Bobcat plateau at 900 FPS with 44.75 grain pellets and 165 bar reg pressure. Backing off to 885 FPS gives 40 good shots in reg from 250 bar fill and ES of 8. Pretty consistent and capable of repeatable MOA at 100 yards. 
 
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Certainly seems possible. My unregulated kral get 36+ shots with the RD Momsters at 875fps from 215bar to 155bar with an ES of 26fps. 280cc tank, 20” barrel. I’ve got it shooting 28gr BTHP slugs at 920fps for 24 shots right now tho, and OH MY GOODNESS is it a LOUD smack when you hit a squirrel at 60uds! My chrony has a tough time picking the slugs up , wonder if I sharpie them if they’ll read better.



That cricket is soooo nive looking, bet it handles like a dream...
 
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The Cricket Mini Carbine has my attention, and I thought I was out of the market.
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Bowwild, I have also been recently looking at the cricket mini carbine. I ordered one from Georgia Airguns a couple weeks ago in .22. I really like the original monte Carlo stock though, instead of the newer skeleton one, so I had Charlie special order me that stock.

Should be here in another week or so.

Can't wait, Scott

1542891943_14913782825bf6a9a7029cd4.56624532_kalibrgun-cricket-minicarabine.jpg

 
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@zx10wall, Derek, not sure the action needs to be enlarged. I measured the port in the action using a piece of clay, and it’s about 5mm, or .197 inches. This is the same dimension @ackuric recommended for the oval dimension on valve and barrel ports. And honestly, even if I needed to enlarge the action port, how would that be done?
 
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Hello Centercut. I use a long shank carbide burr. There are two set screws that secure the firing-valve to the action. I work through the hole for the set screw closest to the air tube or the straight hole as the other hole is angled. It’s directly under the port. 

There are variations in Crickets over the years. It doesn’t sound like you need to enlarge your action port. 

I honestly see no need to oval any port other than the barrel port. Of course, this to accommodate a safe pellet pass over the port. 
 
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