Scope Shimming

Discussion in 'General Airgun Chat' started by Abes, Sep 10, 2009.

  1. Abes

    Abes Member

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    Aquired a Bushnell 4200 8-32x40 am putting it on to EV2 prob is have run out of elevation adjustment (down)
    now i know you can shim the back mount which i have done with a few bits of 35mm film but does not seem to be doing the job, is there anything eles i can do or try, Not sure of the make of the mounts
     
  2. Nealsey

    Nealsey Two Tins

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    Are the mounts true, can you swap them around and the issue remains?

    Other than that, some more shimming is required or get the mounts machined.

    I used an adjustable one piece mount when I had a similar problem with an HW100.

    Not cheap but gives masses of adjustment.

    Neal
     
  3. Abes

    Abes Member

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    Cheers for that mate will give it a try as i said not sure if the mounts are quality ones as came with the scope, would it be worth just buying a new set of decent low mounts

     
  4. RobF

    RobF Administrator Staff Member

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    adjustables :D

    erm... but more on topic... how many have you tried? about 3 should do it unless you have really high mounts...

    (i assume when you've run out, you mean you can't get the turret any higher... yes?)

    if you want to get the turret lower, you need to shim the front...
     
  5. Nealsey

    Nealsey Two Tins

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    Well, change them round first and see, try closing and moving the mounts as far apart as the rails
    will allow, this may gain you something if the mounts aren't parallel.

    Other than that I recommend the adjustable ones, although they take ages to get right.

    Neal
     
  6. Abes

    Abes Member

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    Hi Rob was looking at adjustables but they only do them in Extra High and i want medium (unless you know diffrent)
    up to 6 now :( yer run out mate still firing high by about 4 inches and no down adjustment left, i take it i am shimming the right mount iam doing the rear one not the front

     
  7. villiers

    villiers Self appointed antipimp

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  8. RobF

    RobF Administrator Staff Member

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    yep, thems the business, and they are really fast to setup :) Been using them all year.
     
  9. Photosbykev

    Photosbykev New Member

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    I'm surprised you commented on how long it took to set the mounts. After centring the turrets on my big Nikko I used the adjustment on a set of ATP-66 mounts and it was close to zeroed within a couple of minutes without touching the turrets. A few clicks on the turrets finished the process. Yes they take longer than fixed mounts but it is still only a couple of minutes.
     
  10. Abes

    Abes Member

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    DO THEY DO THEM IN Medium LOL
     
  11. Conor

    Conor Never been banned from sales Staff Member

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    HOLD ON, I may be totally wrong here but remove all shims from the rear mount and shim the FRONT mount. You are shooting high and your scope turret is bottomed out?
     
  12. Abes

    Abes Member

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    State of play so far, tried no shims firing well high not enough turret adjustment to bring it down, so shimmed rear mount, came down but by not enough and still no where near enough adjustment on turret left, so upped the shimms now up to 6 and still the same problem ie still firing high.
    Have now taken mounts off to inspect look ok a very small ammount of overlap though
     
  13. RobF

    RobF Administrator Staff Member

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    abes, if it's firing high then you need to shim the front mount, not the rear...

    normally the problem is it firing low, so the rear is shimmed.

    set the elevation turret to centre, then shim the front to suit. Careful with the amount, the more you shim, the more you can bend a scope by over tightening...
     
  14. Abes

    Abes Member

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    Cheers Rob thats what i needed to know many thanks, have put turret to center ie two and a half turns how many shims would you suggest i start off with
     
  15. RobF

    RobF Administrator Staff Member

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    give it two and see what happens.
     
  16. Abes

    Abes Member

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    Cheers mate thanks for your help

     
  17. Nealsey

    Nealsey Two Tins

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    Sorry chaps,

    I may be a little dense, but how is shimming the front mount going to help with lowering his POI!

    It has already been proved that fitting shims to the rear mount is lowering the POI. So more shims are needed at the rear or try swapping the mounts around.

    Putting shims in the front will raise the objective and therfore exascerbate the problem.
     
  18. Feral

    Feral New Member

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    The way I read it is that is is firing high i.e. the POI is above the crosshair so shimming the front is needed to raise the cross hair up to the poi :confused:
     
  19. RobF

    RobF Administrator Staff Member

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    That's it. :)

    Don't worry, it took me 5 mins to think about it as well... :D

    Yep, when you cant move the turret in a direction, the only option is to move the scope itself... if you need to move the x-hairs up, you need to make the scope look up, but have run out of travel, so shim the front. If you need to move the x-hairs down, then you need to make the scope look down, shim the front so it looks down.
     
  20. CharlieM

    CharlieM Spring Time

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    That amount of error does not sound like something you should be using shims to cure. I usd a bush with double length bkls on my ev2 with no need for shims. Be careful because the length of that scope makes it easy to put under excessive torque through shimming. I would try new mounts and if that doesn't work look at the muzzle brake alignment.
     

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