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Thread: Scope Shims

  1. #1

    Scope Shims

    I need to shim a rifle scope on an air rifle for my father as the scope has no more adjustment upwards but as I cant look down the bore and dont have a bore sighter. I cant remember if I shim the rear or the front scope ring in order I can get the pellet to strike higher on the target. Does anyone know please? My head is telling me the front scope ring but just want to check before I try incase im wrong.

    Many thanks


  2. #2
    If you shim the rear mount you'll effectively be lowering the angle of the corss hari in relation to the bore. Ultimately making the pellet strike higher.

  3. #3
    +1 on what dc 270 said but if its a break barrel mounts for a hw35 are made to compensate for "barrel droop"

  4. #4
    Cheers gents, so totally the opposite of what I was thinking, saved me some head scratching and cursing .



  5. #5

    be careful with shimming as it can sometimes bend the tubes when there is a significant amount of packing required. If the scope and rings are going to be on the gun for a while bedding the scope in the bottom half of the rings with a suitable bedding compound such as marine tex, devcon etc or even jb weld is a better solution. A bit of wax or shoe polish on the tube will stop it sticking to the rings. The angle can then be set but the tube will be supported for the entire contact surface.

  6. #6
    I take it that you've tried swapping the front and rear mounts around? This is often possible on air rifles and .22lr's. JC

  7. #7
    For shim material I suggest you cut a small piece of 35mm film negative to size,hopefully you'll have some somewhere. It's impervious to wet weather and is of a constant thickness,best not to use any more than two thicknesses otherwise you are straining the 'scope as mentioned above.


  8. #8
    you can get 10and 20 moa mounts and rings for such a job.

    what gun?

  9. #9
    carefully does it with shimming , as said it can damage the scope, crimping the tube !!

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