Maths question for someone with brains ?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Down Under Hunter, Mar 20, 2008.

  1. Down Under Hunter

    Down Under Hunter Well-Known Member

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    Happy Easter all !

    The question is this-

    I have my rifle zeroed at 100 meters.

    If I dial 20 moa up, how many inches should the group move up at 100 M ?

    My brain is hurting trying to work this out !

    Remember to convert the yards to meters.

    Cheers

    DUH
     
  2. jwp475

    jwp475 Well-Known Member

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    I believe that it will move it 23 inches....
     
    Last edited: Mar 20, 2008

  3. Willys46

    Willys46 Well-Known Member

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    Check my math

    1.047 / 100= .01047 That is how many MOA per yard
    100 meters= 109.36133 yards
    so there is .01047*109.36133=1.145 moa Per 100 meters

    20 moa * 1.145= 22.9 inches

    That is my guess! it seems close in my book but who knows.

    Willys
     
  4. britz

    britz Well-Known Member

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    I'm comming out with 22.91"

    Using the conversion numbers of 109.4 yards per 100 meters and 1.047"= 1MOA
     
  5. britz

    britz Well-Known Member

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    Took me too long, LOL ;)
     
  6. Willys46

    Willys46 Well-Known Member

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    looks close

    Come on guys--didn't your math teacher tell you you do not get credit enless you show your work! How can we see how you figured it out!

    Looks like we all got some what close.
    We must all be really smartlight bulb
     
  7. britz

    britz Well-Known Member

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    I was in too much of a hurry to show it after I did it on paper -> but I lost the race anyway lol. Besides, History is my specialty not math (got sick of the theroms, postulets, and other things ;) )
     
  8. jwp475

    jwp475 Well-Known Member

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    Take 1.0472 inches which is 1 MOA at 100 yards and divde it by 100 and then multiply the answer by the yards in 100 meters and then multiply by 20 and that is your answer..
     
  9. Down Under Hunter

    Down Under Hunter Well-Known Member

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    Thanks fellas !

    I knew I'd get a bite if I cast that one out there !

    Many thanks again !

    DUH
     
  10. Eaglet

    Eaglet Well-Known Member

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    1 MOA = 0.01'00" = 0.0166667° ----- 100M(Tan(0.0166667°)) = 0.0290888M @100M.
    So, 1 MOA = 29.088822 mm. 1 inch = 25.4 mm
    Therefore 1 MOA = 1.145229" @ 100 METERS
    20 MOA's equals 22.90 inches.​

    This way is more complicated but Willy's46 gave me no choice. He'd already done it the way I would have. Lot of fun! :)
     
    Last edited: Mar 21, 2008
  11. Down Under Hunter

    Down Under Hunter Well-Known Member

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    O.K.

    This will test you all,

    If I dialled 20 moa, and infact shifted the group 25 " in elevation, how many moa will I be out if I ran these numbers at 700 M

    338 edge
    300 smk
    velocity 2830

    alt 200 ft
    temp 80 degrees
    rh 46 %
    bp 30.0

    Just have a feeling that incorrect click adjustments may be throwing my elevation out ?

    Hope the question gives you everything you need to answer it.

    Thanks guys

    DUH
     
  12. Jon A

    Jon A Well-Known Member

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    You need to nail down the click value on your scope, while eliminating other variables (is it securely mounted now? Are you sure it's holding zero?) or you may be chasing your tail for a long time.

    Try a yardstick test at 100. Put the stick vertically on the target. With the rifle very securely held, put your crosshairs on the very top of it and have somebody else crank the turret while you watch the reticle. Ensure it moves smoothly and that each click seems to move the same amount without getting hung up or jumping at all. See how many clicks it takes to get to the bottom of the stick. Do it a few times until you're sure of the answer.

    That will tell you what your scope is doing without including possible errors created by shooter, rifle or mounts.
     
  13. Down Under Hunter

    Down Under Hunter Well-Known Member

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    Jon,

    There is no problem now with the mounts. All rock solid.

    Basically if the previous posts are accurate, for 20 moa dialed on my scope I should get 22.9" up instead of the 25 I accually get " ? That itself will cause grief.

    The rifle simply tack holes groups like I have never seen, but I struggle for good first round elevation dope.

    I gave the 700 M example because I routinely practice on a steel gong at that range, and I would like to know what elevation moa others get when they run the previous mentioned numbers through their PDA. I can then compare that to my adjusted drop chart. If they match I feel I have found the missing piece of the puzzle.

    So basically I'd like to work out the moa diffence at 700m with the 2 " difference from the 20 moa dialed ? Did that make eany sense ? I think from memory you should get around 16.75 up. Would the difference in click adjustments result in a corrected dope of between 13-14 moa for the 700 M distance

    Thanks for your time.

    DUH
     
  14. britz

    britz Well-Known Member

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    If your scope has shifted 25" when you say it should have shifted 22.9" (corrected for MOA to to inches per 100M) that means that your scope is moving 100.9% of what you want it to. Are all of your adjustments moving the bullet 1.09 times what they should be? If so, that means that your scope is not tracking what it is advertised for.