Modified EV2 Mk1

Discussion in 'Air Arms' started by Dale, Dec 21, 2010.

  1. Dale

    Dale Active Member

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    Although the EV2 has never been a preferred rifle for me, a few weeks ago I had the opportunity to pick an example up for a very good price.

    The rifle wasn't 100% perfect condition, but not a dog either. The main thing that had been messed with was the stock - some previous owner had added finger grooves on the grip and carved an extra thumb rest on the rhs of the grip. Worst of all though, the grip hand been shortened by bandsawing out a small section and leaving a piece of laminate loose between the grip base and palm shelf.

    The result of this is it didn't fit my hand, so I removed the shelf and the loose piece of laminate, glued some spacers into position then glued the piece of laminate back into place. I then filled the gap with a metallic effect car body filler:
    [​IMG]
    When the excess was removed and it was shaped and smoothed, it looked OK and more importantly fits properly now.

    The next area I turned my attention to was the barrel. I have never been keen on the EV2 forward barrel collar, and as this example cost me very little, I thought I would do a little experimentation. The muzzle brake and barrel collar were binned. I replaced the barrel support assembly with a modified Fig8 barrel clamp from an S400 with the barrel ring cut off it. This filled the gap between the end plug and the filler cover.

    Being one of the early MK1's it has an S200 barrel fitted rather than the dedicated Lothar Walther item on later examples. Seems to shoot well enough with it though. The barrel fixing seemed a touch flimsy, no the original fixings were absolutely woeful. Three M4x5 grub screws, one retaining the hidden section of the breech shroud, one direct to the barrel and the other onto the brass seal carrier. Take the muzzle end off and the barrel could be waggled around like a limp dick. So radical action time. I drilled two holes at the 4 o'clock and 8 o'clock positions on the breechblock and tapped them to accept two extra barrel retaining screws. Now with three M5 screws bearing on the barrel itself (drilled and tapped through the main breech block and the hidden section of the breech shroud), in a form not unlike a three jaw lathe chuck and the rear M4 screws beefed up to use the full depth of the threaded holes the barrel is much more rigid and suited to floating.

    Finally I made a new decorative muzzle end piece out of alloy to tidy up the appearance of the front end:
    [​IMG]
    After these modifications the rifle is shooting well with no signs of POI shift across the charge. There is sufficient rigidity in the barrel mounting that it will not be knocked out of position by any level of impact normally encountered. If an impact is severe enough to shift it then there is likely to be other collateral damage to the rifle. I deliberately designed the muzzle end to fit flush with the front of the filler cover to prevent it snagging or being easily bumped.
    [​IMG]
    The extra barrel retaining screws can be seen as the black dots below the forward scope mount. The screws are M5 socket set 'grub' screws.

    The next phase of the project will be to make a means of attaching a rubber butt pad to the rear assembly, as despite trying I find the AA design butt plate difficult to get comfortable with. It lacks the ease of vertical adjustment that I favour with the rubber pad as fitted to my Pro-Target. I will also fit longer hamster posts, and already have the stainless bar stock to make them.
     
    Last edited: Sep 3, 2018
  2. RobF

    RobF Administrator Staff Member

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    nice to have a little project :)
     
  3. rich

    rich Active Member

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    Nail on the head, Dale. A poorly fitted barrel was exactly the problem I experienced with mine when I tried to free-float it. The three M4 screws all in the same plane do nothing for stability, and it all depended on the barrel being a close if not an interference fit in the body of the action, which it wasn't. You've planted an idea now and I might just have to give you the compliment of copying your 3-jaw fixing system. ;)

    Nice job.

    About the CZ barrel; I assume mine must be, it was an October 2004 build, a year older than yours. My S400 - the one that you extended - shoots better groups.
     
  4. TonyF

    TonyF SWEFTA FT Champion 2006

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    Nice one Dale, looks a good job and I will be interesting to see it at one of the SWEFTA shoots.
     
  5. Magic Bus

    Magic Bus New Member

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    Interesting solution there Dale, especially as I have a MK1 too. Thanks for showing.
     
  6. Dale

    Dale Active Member

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    I am assuming it is a CZ barrel as when the conical breech shroud is removed there are three small 'dimples' on the upper side of the barrel that you see on the S200 where the forward scope mounting block goes, plus a cross slot at the muzzle for the muzzle end piece screw to lock into.

    One thing I will say with doing the modification - the biggest thing was summoning up the courage to take a drill to the breech block. Definitely invalidates any warranty!!
     
  7. berty177

    berty177 Judge Diva

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    CZ barrel

    Dale,

    I got one of the older EV2 barrels here, I aquired it some time ago as a favour.

    I have been told it is a damn good barrel, so thinking of having it made to fit my hft EV2, the old owner told me it was one of the best barrels he has ever used and he has had a few guns in his time...


    Berty
     
  8. Dale

    Dale Active Member

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    Well when it comes to the CZ barrels, you rarely seem to hear of a duff S200, so it doesn't surprise me they can work well, just the original fitting is not as good as it could have been.

    This EV2 groups nicely, but I have found it has the dreaded reg creep and if left for any decent length of time it throws the first shot low, but after that it is fine until left again.

    I am just waiting on a new reg part to be delivered to get it sorted.
     
  9. rich

    rich Active Member

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    I know you have strong hands :eek: but how did you manage to get the reg undone? :)
     
  10. Dale

    Dale Active Member

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    I haven't yet as I am still waiting for the bit to be delivered.

    Anyway I don't need to remove the reg itself, only the cylinder and I am prepared to use a destructive method to get it off if it won't unscrew by normal methods (I have ordered a new nickel plated spare just in case). If it won't give easily then I will drill through the tube to fit a cross-bar lever to screw the SOB off.

    The problem area is the shut-off valve seat which can be removed with the body of the reg in-situ. Air is bleeding past this seat and overpressuring the valve hence the drop. There are no air leaks from anywhere else so that is the only thing it can be.

    With the floated barrel I won't need to screw the cylinder on silly tight in the future. As far as the reg goes I will make a tool for that job as and when it needs doing.
     
    Last edited: Dec 22, 2010
  11. rich

    rich Active Member

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    Mine too has the cross slot at the muzzle end; I can't recall about the dimples near the breech end. That makes it a CZ then.

    Yours is a much improved engineering solution, not relying on alloy threads creamed up stupidly tight.
     
  12. Dale

    Dale Active Member

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    I believe so as it seems to share characteristics with an S200 barrel.
     
  13. JTK

    JTK New Member

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    Dale, best tool I saw was some gent that took a hex nut that fitted over the tube then drilled and tapped three grub screws that fitted into the reg holes. Cant find the pic now but was a great idea.
     
  14. Big Dave

    Big Dave New Member

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    I've seen the picture mentioned and have copied the tool. I'll post a pic later this evening.
     
  15. Big Dave

    Big Dave New Member

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    It's not the prettiest piece of engineering but it works......
     

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  16. JTK

    JTK New Member

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    thats the one BigDave. cant imagine a reg being unwilling to let go with that attached :D
     
  17. Dale

    Dale Active Member

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    Over the Christmas break, I decided to tackle the regulator issue. The first hurdle was to get the compression tube unscrewed from the regulator given AA's solution to POI shift of torquing them up extremely tightly. As a precaution I had already purchased a replacement tube just in case removing the old one damaged it. With the action clamped in a soft jawed vice I made every effort to remove the old cylinder without harming it. Even with a large BOA strap wrench it was not coming free. Eventually I decided to be a bit more drastic and the application of a vice grip shifted it - damn glad I had bought a replacement in advance!

    With the cylinder off the rifle the offending part of the regulator could be accessed. Prior to removing the valve seat assembly I measure the distance it was screwed in to replicate the reg pressure on reassembly. When the valve seat was removed the source of the reg creep became clear - a significant ring mark was present in the face of the synthetic valve seat. It appears that the reg pressure may have been changed at some point without facing the valve. The regulator probe creates a witness mark in the valve seat through normal operation, if the valve seat is rotated without re-facing the sealing can be affected.

    [​IMG]
    Above - the key components of an AA regulator (these parts are from a Pro-Target regulator I serviced some time ago, but are the same as the EV2 regulator parts). The problem part in my EV2 was the right hand component with the white synthetic seal. The flat upper surface had a considerable ring mark from where the sharp edge of the piston probe (left) had cut into it. While such a ring mark occurs normally, in the EV2 reg it was allowing air to bleed through when it should have been sealing totally. The valve seat in the picture has been polished smooth prior to re-assembly.

    The next step was to carefully polish out the ring mark on the EV2 component to a smooth flat surface, then it was reassembled to the correct position. The new nickel plated cylinder was then added, which caused some fun keeping the pressure gauge/spirit level assembly in the correct orientation. With the barrel being floated there was no need to screw the cylinder on as tightly, it is now removable with the BOA wrench for future servicing.

    With the rifle reassembled it was time to fill and test. Initially velocity had crept up, so it was set back to my preferred setting of around 755-765fps and the rifle left initially for 10 minutes then fired over the chrono - no velocity drop, the rifle was then left 1 hour and tested - again velocity was within my setting parameters. Finally the rifle was left overnight and tested and again first shot was exactly where it should be within my chosen velocity spread. I will continue the monitoring over the next few days, but from initial results, it seems to be behaving properly now.

    [​IMG]
    Rifle with nickel plated cylinder fitted.

    [​IMG]
    [​IMG]
    Detail view of one of the extra barrel retaining screws.
     
    Last edited: Sep 3, 2018
  18. Jon

    Jon Member

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    Sounds like you had an easy one to do then Dale, usually grossly over tightened to deter attempts at tinkering the last few years.
    No amount of tightening will cure deflection on thin wall tube, it will veer off exactly the same.
     
  19. DazF

    DazF Active Member

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    Nice work as usuall Dale. :D
     
  20. Dale

    Dale Active Member

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    Tried the rifle on the chrono on the 8th January after not using it for a week - 1st shot velocity right up where it should be so it looks like the problem has been cured by the above mentioned work.
     

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