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Thread: Shimming of scopes

  1. #1
    Sharp Shooter

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    Default Shimming of scopes

    So I bought the Hawke Vantage 2-7 x 32 AO scope as suggested in another thread.
    It seems like a nice scope and it is so much clearer than anything I own at 8 meters and less
    Problem just is, the scope is much shorter than I thought. So now the rear part of the scope is touching the action of my rifle when I want to mount it on my low weaver rings. But we are not talking much, so I think about shimming it rather than using it with high mounts.
    I''ll be shimming front and back, so the scopes tube should not bend.
    Question is, how much can I shim before it can become an issue? What material do you use to shim your scopes?
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  2. #2
    Sharp Shooter

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    I use Xray film cut into appropriate strips. It gives 0.1mm or so per strip. It's hard enough that it doesn't thin out under moderate clamping forces. One or two strips in the bottom rear ring is enough to give a bit more scope elevation for longer ranges. If you use rings that come with mounting tape and don't overtighten then it doesn't damage the scope tube even though sitting at a tiny angle in the mounts.

    In your case, for a clearance issue I'd think about rather changing to medium rings. The various manufacturers all have different dimensions for their low, medium and tall rings so if you look up the dimensions on their websites you might even find that another manufacturer's low rings are a bit higher than yours and would be suitable.
    Last edited by JXV; 10-09-19 at 12:06.
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  3. #3
    Sharp Shooter

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    Quote Originally Posted by JXV View Post
    I use Xray film cut into appropriate strips. It gives 0.1mm or so per strip. It's hard enough that it doesn't thin out under moderate clamping forces. One or two strips in the bottom rear ring is enough to give a bit more scope elevation for longer ranges. If you use rings that come with mounting tape and don't overtighten then it doesn't damage the scope tube even though sitting at a tiny angle in the mounts.

    In your case, for a clearance issue I'd think about rather changing to medium rings. The various manufacturers all have different dimensions for their low, medium and tall rings so if you look up the dimensions on their websites you might even find that another manufacturer's low rings are a bit higher than yours and would be suitable.
    Ain't that the truth. That makes it so difficult to buy what you want. Dimensions should be a must to all shops selling scope mounts.
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  4. #4
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    Beercan is perfect, because it allows accurate shimming, but with some enjoyment beforehand too.
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  5. #5
    Sharp Shooter

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    Quote Originally Posted by Bludlust View Post
    Beercan is perfect, because it allows accurate shimming, but with some enjoyment beforehand too.
    I am sure you shim ALL your scopes. Just to have an excuse
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  6. #6
    Sharp Shooter

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    Quote Originally Posted by Bludlust View Post
    Beercan is perfect, because it allows accurate shimming, but with some enjoyment beforehand too.


    Beer and cold drink cans are thin steel sheet and may rust over time so maybe consider adding a thin little smear of grease to the surfaces before you clamp them down...and beware the sharp edges.
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  7. #7
    Sharp Shooter
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    You must have very old cans then. :-)
    Beer and cold drink cans of today are all Aluminium.
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  8. #8
    Sharp Shooter

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    Quote Originally Posted by DSF View Post
    You must have very old cans then. :-)
    Beer and cold drink cans of today are all Aluminium.

    Aaah yes...that snuck past me. In South Africa the switchover started late 2013. That old can you keep in the garage for making shims may still be steel with an alu top. If using newer cans it should be alu. Some corrosion is still possible and the grease trick will still work. I have lots of Xray film which I prefer
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  9. #9
    Sharp Shooter
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    Film negative and x-ray film. Film negative is thin enough for fine tuning while the thicker x-ray film is better when more adjustment is required and you do not want to stack too many shims. I can't say how much shimming is too much before it becomes a problem but I always try to keep shimming to an absolute minimum. If I have have to stack more than two x-ray thickness shims then I look for an alternative.
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  10. #10
    Sharp Shooter
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    Seriously, just get some new mounts rather trying to fudge it with shims.

    Years ago I used to shim scopes to get the results I wanted, but, having seen the results on a number of occasions now where people have crimped or in extreme cases caused a crush in the scope tube, I now no longer shim.

    I would now much rather use mounts that are either drop compensated, adjustable or use an angled base.

    The best mounts I have come across for dealing with any alignment issues are Burris Signature Zee Rings with the adjustable inserts, perfect alignment and no damage or marking of the tube.
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  11. #11
    Sharp Shooter
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    The adjustable mounts tend to be pricey.

    A cheaper alternative that I used is beer can shims (as recommended by Blud), stuck to each other and to the mount with very thin double sided tape that the missus use in her crafting stuff. This helps that the shims stay put if you want to adjust, move or loosen the scope.

    To prevent tube crushing I added M3/M4 (can't remember) spring washers to each of the scope mount screws and tightened the whole shebang just enough to compress the spring washers flat.
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  12. #12
    Sharp Shooter
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    Quote Originally Posted by Phats View Post
    The adjustable mounts tend to be pricey.
    So are decent quality scopes, hence why I nowadays prefer not to use fudge methods.
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  13. #13
    Sharp Shooter
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    Totally agree with you. In my case I could not justify paying more for mounts than what I paid for my scope (used).

    Some of the low cost adjustable scope mounts did not inspire much confidence in me after looking at how they were put together.
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  14. #14
    Sharp Shooter
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    As always you get what you pay for.

    With scope mounts I will no longer buy any of the 'budget' stuff because the quality of the materials and engineering is generally kak.

    You will no doubt be familiar with the old saying that "a chain is only as strong as its weakest link" given how much we tend to spend on the guns and scopes it is false economy to suddenly get all tight-fisted with the mounts.

    You might buy a used scope, but if it is quality then treat it to quality mounts.

    In terms of adjustable mounts, if it is simply a case of a scope running out of elevation adjustment (more prevalent with 1 inch tube scopes than 30mm) then I prefer to buy either Sportsmatch or BKL droop compensating mounts - these are fixed but with a built in slope to eliminate the need to shim.

    If the needs are more involved then the aforementioned Burris Zee Rings or the Sportsmatch Mounts are the minimum I would look at.
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