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  1. #1
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    Default Determining cross hair height above bore

    Hey guys,

    How do you go about determining the height of your cross hair above your bore for trajectory calculations (like one does on the JBM Ballistics calculators)?

    I have been using a standard of 1.6 inches (40.6mm) when I have a 40mm ocular bell.

    What is the proper methodology though?

  2. #2

    Default Re: Determining cross hair height above bore

    Following with interest. I use the Meopta App and I'm also not sure how exactly. So far I place my rifle in a vice and use a metsl rular on top op the barrel just in front of the front objective. But my barrel is lower at the crown "If that makes sense"

  3. #3
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    Default Re: Determining cross hair height above bore

    Is variation of 5-10 mm going to make any practical difference? I believe not. In any case, I put my rifle on the bench, dial to lowest magnification, have another person holding a ruler at the crown and then read of through the scope where the cross hair is marking on the ruler. It does happen that focus is bogus, so then I just use a brightly coloured ruler and move a piece of paper over the ruler until the difference in colour is at the cross hair and the helping hand can then read on the ruler where the paper line is at this stage. Crude, but seriously, that 5-10 mm at the bore has as good as 0 influence on practical shooting.

  4. #4

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    Quote Originally Posted by Adoons View Post
    Is variation of 5-10 mm going to make any practical difference?
    Apparently not that much at all





    One setting is 40mm and the other 50 mm

    Seem I've over done the re-sizing. My apologies for the poor quality.

    Anyway, biggest difference is 6 meters between the two.

  5. #5
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    Default Re: Determining cross hair height above bore

    Measure bolt and ÷ 2, measure scope main tube and ÷2. Measure gap between bottom of scope tube and top of bolt, add results of above and you have height above bore.

  6. #6
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    Default Re: Determining cross hair height above bore

    @killzone - what app is that? I like using Strebor, but I would love to get my hands on some more apps, specially ones with more free features.

  7. #7

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    Quote Originally Posted by Toxxyc View Post
    @killzone - what app is that? I like using Strebor, but I would love to get my hands on some more apps, specially ones with more free features.
    It's the Meopta App Tox. So, It will only work with Meopta scope I assume.

  8. #8
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    Default Re: Determining cross hair height above bore

    Aww, bummer. Thanks anyway! Back to Strebor I go...

  9. #9
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    Default

    Quote Originally Posted by Marc05 View Post
    Measure bolt and ÷ 2, measure scope main tube and ÷2. Measure gap between bottom of scope tube and top of bolt, add results of above and you have height above bore.
    I'll try this thanks.

  10. #10

    Default Re: Determining cross hair height above bore

    I just measure the bell of the scope + the barrel in line where I measured the bell divided this by 2 + the gap between bell and barrel also in line where I measured the scope bell and you have your sight hight.



    Sent from my iPhone using Tapatalk

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