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POI Question

Discussion in 'Shooting Related Threads' started by mikkeeh, May 11, 2013.

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  1. mikkeeh

    mikkeeh Active Member

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    OK.....So my buddy has a CG that he recently bought, but has not patterned yet. He says that based on the info CG puts out....it should be shooting around 90/10. My 680 is also shooting 90/10. We try a pattern board at 13 yrds. We use the same ammo, and each shoot both guns. His gun hits 2 3/4 inches high at 13yrds. Mine hits dead center. Now............We move the pattern board to 33 yrds. His patterns 90% high. Mine patterns 90% high. Can someone explain this to me??????? How can they be almost exactley the same at 33 yrds......and that much different at 13 yrds??
     
  2. Garry

    Garry Active Member

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    "How can they be almost exactley the same at 33 yrds......and that much different at 13 yrds??"

    Short answer is they can't if you are using the same identical sight picture when the gun is fired. Are you and your friend shooting both guns from a stable rest?

    Also, 2 3/4 inches high at 13yds extrapolates to 7 inches high at 33 yds.

    7 inches high at 33 yds would equate to a 74/26 POI.

    My guess is your not using the same identical sight picture. This is not uncommon because at 33 yds what looks like the same sight picture used at 13 yds might not be the same.
     
  3. Neil Winston

    Neil Winston Well-Known Member

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    1a. First question - is your gun an un-single? 1b. Is his?

    2. And did you shoot off a rest, as Garry already asked?

    3. How did you determine your 90%-high figure?

    4a. How many shots led you to your conclusions, both at 13 and 33 yards? 4b. Was that measured yards?

    Neil
     
  4. mikkeeh

    mikkeeh Active Member

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    Neil:

    Both guns are unsingles.
    Both shot from a rest
    90% was a guesstimate as most of the pattern was above the point of aim.
    6 shots at each distance.
     
  5. Neil Winston

    Neil Winston Well-Known Member

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    All that sound just great, mikkeeh, just one more thing . . .

    As I remember, a 680 un-single has an almost-flat rib, right down the receiver to the bead. How about the CG?

    Neil
     
  6. mikkeeh

    mikkeeh Active Member

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    Neil: I dont have the CG here right now. My 680 has an add on delrin rib by Dave Berlet. A quick measurement show about 7/32 lower at the muzzle.
     
  7. Neil Winston

    Neil Winston Well-Known Member

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    Well, I really don't have an answer, though it think your question will find part of its solution in comparing where the center of the bore of each is relative to the bead, and your 680 will turn out to have a larger distance there.

    Once you know the relative dimensions you can use section 5, pages 4 and 5 of the above-linked guide do see what the predicted POI's are, but use about 1.5 as a multiplier rather than the 2 intended for 40 yards.

    Then use a measuring tape to judge where the pattern center is, not in percentage above (like 90) but rather distance in inches and I think most of your concerns will fade away. But it sure is an interesting problem you have given us!

    Yours in Sport,

    Neil
     
  8. Garry

    Garry Active Member

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    My guess is your not using the same identical sight picture for all shots. This is not uncommon because at 33 yds many of us cannot see as good as we do at 13 yds. What looks the same might not be the same.
     
  9. mikkeeh

    mikkeeh Active Member

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    Garry: Possible I guess. But we both shot both guns at both yardages......Still seems strange to have identical results.
     
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