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POI Question

Discussion in 'Shooting Related Threads' started by TD1958, Mar 22, 2010.

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  1. TD1958

    TD1958 Member

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    I know this has been discussed on hers but i could not find the old thread. My gun shoots approx. 2 in. high at 13 yards. What is the calculation for POI at 40 yds. Thanks, Tim
     
  2. Trap2

    Trap2 Well-Known Member

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    Tim... If your gun shoots 2" high at 13 yards, it will shoot 6" high at 39 yards. In percentages, your gun shoots a 70/30 pattern at 39 yards.... Dan Thome (Trap2)
     
  3. Classic Trap

    Classic Trap TS Member

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    The calculation is done by using a simple cross-product algorithm (pre-algebra). Ask any junior high kid for help! 2"/13 = N"/40 This will work for any known ratio to compute an unknown. Same same as if I can buy 7 apples for $2.00 how many apples can I buy for $3.75? If my POI is 5" at 16 yd, what is my POI at 40 yd? 5"/16 = N"/40. Do the math, its easy and fun and you can compute the POI at any distance. (at the distances we shoot, its really linear and you get a very accurate one-to-one correspondence)
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    It's close enough, assuming your gun isn't some high-rib Special, but to say it's linear is not true, since the effect of gravity is not linear. It's not even true to say it's very accurate but it's OK if you aren't very fussy.

    We only get away with such rough approximation because once you know your 40 yard POI there's nothing you can do with it anyway. If the number made any difference, we'd work to get it right.

    Dan, once you know where a gun shoots, what does that percentage stuff add? Let's just let it die a deserved and un-regretted death.

    Neil
     
  5. phirel

    phirel TS Member

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    Classic Trap- Your calculations will not work, as Neil stated. The 3X the height at 40 yards works fairly well for most guns because the height from the bore to the front sight cancels out the fall due to gravity reasonably accurately at 40 yards.

    Pat Ireland
     
  6. Trap2

    Trap2 Well-Known Member

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    Neil.... I would love to, however, you KNOW there ia always someone that just HAS to know the percentages rather than the actual figures...... Dan
     
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