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Question on POI

Discussion in 'Uncategorized Threads' started by gasman03, Apr 8, 2008.

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  1. gasman03

    gasman03 Member

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    I know all guns pattern different but when checking the POI is there a base to go off of to get your gun close to the set point you want it at. For example I am checking the POI of my gun. I am setting on a bench at 13 yards from my target and I want my gun to be 60/40 how many inches above center to i want to be? Also for 70/30-80/20 and so on. Any ideas?

    Corey
     
  2. setter

    setter Member

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    Here's Pat's formula:

    "Multiplying the number of inches high at 13 yards by 3 is not a bad estimate of the POI. A bit more precise estimate would by the inches high at 13 yards times three, minus 3 inches (fall due to gravity) plus three times the distance from the center of the bore to the front sight.

    Pat Ireland"

    Then there was the "BIG" debate thread above.
     
  3. Rollin Oswald

    Rollin Oswald Active Member

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    And even Pat's precise estimate completely ignores the coriolis effect.

    Rollin
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    An inch high is a pretty good match for the number you are after, Corey. Close enough, anyway, And added inches about (somewhat less than) 10% as the patterns drift up. All this is based on "reasonable estimates" which is all the closer it can be done as a practical matter. My notebook says "An inch high" or "two inches high" but I never really took a scale out there; I just write what it looks like.

    Neil
     
  5. gasman03

    gasman03 Member

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    So are you telling me an inch high at 13 yards if about 60/40 and 2 inches is 70/30 and so on?
     
  6. phirel

    phirel TS Member

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    One inch high at 13 yards is approximately 60/40. Two inches high at 13 yards is approximately 70/30.

    Two inches high at 13 yards would be 5-6 inches high at 40 yards.

    I am almost alone at my position of how to best use the POI information gained from 13 yard tests. First I don't like to use the terms like 70/30. Nearly everyone on the line will tell you their gun shoots 60/40 or 80/20, but these numbers are only guesses. If a person with a gun that they believe shoots 70/30 can accurately measure 5 patterns he is likely to get something like : 63/37, 66/44, 72/29, 74/26, 76/24. None of the patterns will be 70/30. If the average % high plus or minus one standard error is calculated, it becomes clear that these numbers have no significant meaning.

    First, and most important, the POI at 13 yards will tell you if your gun shoots to the right or left. Either is very bad. Next, the POI at 13 yards will tell you if the gun shoots flat, a little high or a lot high. You can determine the number of inches high the gun shoots with some accuracy, but accurately converting this to % high becomes difficult.

    Also, it is important to remember that testing a gun from a rest tells you only where the gun shoots. That may, or may not be related to where you shoot the gun.

    If we could launch 6' X 6' sheets of paper at 42 MPH, with an orange target painted in the middle, we could get some solid information about how high, or low, both the gun and the individual shoots.

    Pat Ireland
     
  7. gasman03

    gasman03 Member

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    Thanks you Pat.

    Corey
     
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