Shimming the rear mount.

Discussion in 'Long Range Scopes and Other Optics' started by Nodak7mm, Jan 13, 2007.

  1. Nodak7mm

    Nodak7mm Well-Known Member

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    Jun 18, 2001
    I want to add 20-25 MOA to my scope and intend on shimming the rear mount. Wondering is there an approximation of x-amount of shim material equals approximate MOA?

    Shimmed another rig of mine couple yrs back, but cant remember how much shim material I used..

    Thanks.

    Rod
     
  2. Desert Fox

    Desert Fox Well-Known Member

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    Jan 31, 2002
    For long range shooting, shimming is not the answer. Get a one piece base with 20 MOA slope. Shimming can introduce stress in the scope if not done correctly. The key to proper scope mounting is to eliminate stress associated with misaligned mounting components. If you elected to stay with your current set up, then I recommend to replace your ring with Burris Signature with Pos-allign offset insert. This is better than shimming the rear base. You have to buy the insert seperately though.
    http://www.burrisoptics.com/sigrings.html
     

  3. Buffalobob

    Buffalobob Writers Guild

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    I believe that if you run "Search" on "shim" you will find at least three threads that give the equation you need to use.

    If my memory is reliable, which I doubt it is because I can't remember the last time I was wrong, you will need 0.001 inch per MOA for a short action.

    As mentioned, shmming a 2 peice base 20 MOA will require the rings to be lapped or else you will severely mark the scope tube.
     
  4. Nodak7mm

    Nodak7mm Well-Known Member

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    Jun 18, 2001
    Yes I am aware of the potential misalignment and the necessary lapping to ensure a stress free mount. However, thanks for keeping an eye out for me. /ubbthreads/images/graemlins/wink.gif

    The reason I am considering doing this is; I need the MOA because I am wanting to shoot Monday and there is not a tapered 1 piece base or set of signature rings to be found in this town.. /ubbthreads/images/graemlins/mad.gif

    Ta heck with it, too cold to go shooting Monday (looking at -10), I 'll just order the proper equipment and "do it right once".

    Thanks for the responses.

    Rod