Measuring Scope Height with a 20MOA Rail ??

Discussion in 'Long Range Hunting & Shooting' started by .25MOA, Oct 4, 2010.

  1. .25MOA

    .25MOA Well-Known Member

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    Hi Guys,,,yes it's probably been asked before but i cant find a clear answer ?? Is it possible to do ?? where do we measure from ?? I have measured from firing pin to centre of the scope mounts.....as the rail is higher at the rear, is it better to measure at the objective ???

    Cheers, Ray.....
     
  2. YubaDirt

    YubaDirt New Member

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    Does anyone have an answer to this? I would also appreciate the help.
     

  3. Timmyatneb

    Timmyatneb Well-Known Member

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    Ive always measured scope tube and bolt diameter, and distance form bolt to scope. Take half the tube half the bolt and add them numbers to distance between tube and bolt. Always work great for me out past a thousand.
     
  4. kcebcj

    kcebcj Well-Known Member

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    I measure center of the bolt to center of the tube at the center of the elevation knob. In my pea brain and limited knowledge of the modern rifle scope that is the place that makes the most sense to me.

    Someone with a more working knowledge of a rifle scope should chime in as to whether it makes a difference as to where in the elevation scheme your zero lies. I use a 10MOA base and where the scope is zeroed leaves about 45MOA up so it is zeroed off center. Does that make a difference?

    In my setup a 1/8 inch difference 1.75" verses 1.875" equals a .5 MOA difference in Exbal at 800 yards. Measuring at the center of the elevation turret very carefully has worked OK for me as far as I can tell and that adjustment is 1.875".

    On another note that is another adjustment one can make when proving a drop chart and trying to make all points of impact agree with the generated chart especially farther out even though I have not done that....food for thought.
     
  5. C.O. Shooter

    C.O. Shooter Well-Known Member

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  6. Broz

    Broz Well-Known Member

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    This is what I do too and it makes sense to me. If there is a better way or reason to do it different I would like to know.

    Jeff
     
  7. calib

    calib Well-Known Member

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    tell me if this is wrong, i measure the scope objective bell/ by 2, then measure the diameter of the barrel directly below that and / by 2 then add those two numbers to the distance between the bell and barrel rite?
     
  8. theo98

    theo98 Well-Known Member

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    Close. A 20 moa cantered rail would be a little off, thus I use...

    Formula= (Scope's "Tube Diameter"\2) + (Bolt's "Diameter"\2) + (Distance between bottom of scope tube and top of bolt in middle of tube area equally between ring mounts) = Scope Height!

    Just as C.O.Shooter posted!

    http://www.accurateshooter.com/optics/determining-scope-height-above-bore/
     
  9. calib

    calib Well-Known Member

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    Im gonna have to try it and see how far off it is. Thanks
     
  10. Catfur

    Catfur Well-Known Member

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    My best guess would be that the optically correct location to measure the height to would be the center of the exit pupil (if you can find it).
     
  11. yobuck

    yobuck Well-Known Member

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    there comes a point where its best to accept easy answers unfair as that may seem at times. which is another way of saying just go shoot the freakin thing.
     
  12. Wile E Coyote

    Wile E Coyote Well-Known Member

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    Well said!

    Out of curiosity, I just ran the data, on Exbal, for one of my rifles at 1000 yds. The elevation at that distance came back as 28.25 MOA. I then went back and only changed the scope height from 1.75" to 2.0". That elevation came back as 28.0 MOA.

    1/4 MOA change at 1000 for a 1/4" difference in scope height.

    I just wish I had a place to shoot at 1000 to demonstrate it!


    Pete
     
  13. minute of elk

    minute of elk Well-Known Member

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    As previously mentioned, measuring & adjusting to fit dope seems to work the best for me. I measure at the turrets, then tweak it to fit actual poi at range