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 Post subject: Project .223 Windy City
PostPosted: Wed Aug 28, 2019 7:01 pm 
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Joined: Tue Feb 18, 2014 7:24 pm
Posts: 667
Location: Dowling ,ontario
I received this rifle today and after putting a few shots over the chrony for a base line started the disassembly . I was quite surprised when I measured the barrel with an AOL of just 17.5” . I will be replacing the barrel with a .222/ .223 liner that Brownells sells in 26” length. First on the agenda is to replace the heavy bottle with a .5L Acecare carbon fibre bottle from Aliexpress . I purchased the rifle used with an Altaros regulator that screws on between the drop block and bottle , the plenum size is unknown but I hope to have that measured up using a liquid . Next up , air flow . I measured the porting and there are quite a few restrictions . First is the path between the plenum and the valve inlet , there was a centre hole at .121” and four other holes staggered around it ( didn’t measure them ) . I opened that up to .275” and blended the entrance into the drop block . The valve stem itself is .155” and the port is .305” which isn’t horrible but I’ll be replacing it with a peek poppet and a thinned our stem . Next is the valve outlet, which is similar to the Hatsan valve with multiple holes around the circumference . This works but is not my preferred method for managing air flow . I’ll be doing the Bob Sterne trick and use setscrews and open up the hole that lines up best with the transfer port through the action . Next is the transfer port through the action , it measures at only .173 “ and that will not work for making the power I’m looking for . This is going to be tricky to open up as the transfer port gets drilled out using one of the barrel securing setscrew holes . I’ll have to think about how to get it to at minimum .223”. Last is the barrel . I haven’t thought that part out yet , all I know is it is 5/16” OD and the action is 11mm . I’ll most likely use a thimble similar to the FX Crown continuum barrel set up .


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PostPosted: Thu Aug 29, 2019 6:53 pm 
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Joined: Tue Feb 18, 2014 7:24 pm
Posts: 667
Location: Dowling ,ontario
Made some pretty good progress . Got the thimble made up complete with the inner oring . Talk about pucker factor . There sure wasn’t a bunch of room for the barrel ports and the oring grove . With the measurements I came up with a total barrel length of 22 1/8” with the existing shroud and the barrel extending all the way to the front barrel support /end cap. I’m still having a hard time figuring out how to get the biggest ports possible . The orings on the valve block are only spaced out by .185” and that’s cutting into the material holding the orings . Ill get some pics up as soon as I get this sorted out . I figure another couple hours of machining and measuring and it should be ready to test .

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PostPosted: Fri Sep 06, 2019 4:24 pm 
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Joined: Tue Feb 18, 2014 7:24 pm
Posts: 667
Location: Dowling ,ontario
Got some more work done . In the pics you can see the thimble that I spun up . The channel and ports are at .173” . I turned down the end of the barrel for a slip fit into the shroud endcap and it is slightly compressing the barrel . I still have to make some delrin spacers for keeping the barel centered in the shroud . The valve outlet ended up getting the top port oblonged to .173”x .275” roughly . I drilled the transfer port straight through the action and went up to .2” as that’s all the room I have between the orings on the valve . I did some chrony testing and with the regulator set to 150 bar , I was only able to get 52fpe shooting some 31 grain BBt’s . I then figured I should remove the regulator as it was most likely the small plenum causing the low velocity . I haven’t put it on a scale yet but I’m sure it lost close to 5 lbs between the barrel and air cylinder being removed .
Once removed I filled the gun to 155 bar and ......... 1048 FPS good for just over 75 FPE . ( luckily my wife is used to my chrony work in the basement ) this one is loud . One thing I did notice while working over the internals is the hammer throw , with the long valve stem the hammer travel is just over an inch . There’s over 5/8” of stem protruding and if I were to shorten the stem ( most likely gonna happen) can go to a max of 1 1/2” of throw . This should allow me to use a lighter hammer and spring combo .
I have a few more small jobs to do but it’s shaping up and I’m getting real close to my goal . Last pic is the WC with its “little sister” the K550. I’m going to have to find a scope for this one .


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AC84C746-72BE-4013-9D9A-6A1DD7A6B68E.jpeg
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PostPosted: Fri Sep 06, 2019 4:27 pm 
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Joined: Tue Feb 18, 2014 7:24 pm
Posts: 667
Location: Dowling ,ontario
Got some of the last few items cleaned up . Made some liner spacers to keep the liner centered in the shroud , I shortened the valve stem to .225” from .585” . Last thing would be to get a double spring set up , I had to turn down the existing spring guide for a slip fit for the inner spring . Voila , fill the gun to 200 bar and the first shot over the chrony was 1115 fps with a declining ten shot string ending at 1060 fps at 170 bar. I’m sure I could get more out of her but porting is holding it back . My goal power wise is just about spot on and I’ll actually have to dial it back a bit .
I contacted Altaros to get one of their plenum extensions for the regulator for this rifle . I beleive the total plenum will be close to 30cc . Using rough math and previous experiments as a prediction , I think with the reg set at about 180 bar 75 Fpe with 39 grain bullets should be doable .


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603F20AB-EDFB-4634-A8F6-498159CC9D76.jpeg [ 248.6 KiB | Viewed 225 times ]

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