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Thread: Wind at 100 yards

  1. #1
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    Wind at 100 yards

    We shot Sunday and the wind was blowing but not crazy by any means. We shot a lot of groups with 6 different rifles and everything was blown right. I should have taken a picture of the target. Not a huge amount but an inch to 1.5 inches. I have discussed this in the past, but how much does wind effect 556, 308, 300WM at 100 yards. ie 5 or 10 mph.

    Maybe it was not the wind but it was just nuts how EVERYTHING hit right.

    As a side note, we were testing my new LMT MRP 10.5 that Brownells had on sale for $699. The 8X Burris XTR scope is not ideal for shooting groups as the reticle has little dots that are hard to see on a target at 100 yards so we shot a couple groups at 100 that were 1.5 to 2 inches which isn't bad for scope and 10.5 then I said , lets try 50 yards and see what happens, .5 MOA at 50 yards. I think maybe some wind and some scope limitations explains that situation.

    PB
    Last edited by Pappabear; 10-01-18 at 08:03.
    "Air Force / Policeman / Fireman / Man of God / Friend of mine / R.I.P. Steve Lamy"

  2. #2
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    With .308 175gr SMKs at 2500 at sea level (0 ft DA), each MPH of full effect wind will move the projectile .03 mils per 100 meters (roughly) out to about 600 meters, at which point it will start to increase.
    6.5mm CM 130gr AR Hybrid at 2890, each MPH of in-effect wind will move the projectile .02 mils per 100 meters out to about 700 meters.
    Wind is a thing. I could go on at length about determining/predicting wind effect, but it's really hard to effectively communicate those concepts over the internet in a short time.
    Jack Leuba
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    Knight's Armament Company
    jleuba@knightarmco.com

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  3. #3
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    So strange. We've seen this before. Where EVERY gun we shoot is pushing one direction or another. We'd have needed a full value 10 mph wind to tie out to the numbers above. I just don't think we were in that much wind.
    "You people have too much time on your hands." - scottryan

  4. #4
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    Unless people spend a lot of time and effort in precisely tracking wind, they usually aren't very good at it, so that whole variable makes it hard to diagnose cause of shift.
    There's a litany of possible inputs that can cause minor shift, but 1-1.5 inches at 100 is not insignificant, and would warrant some investigation if I was seeing it in my guns.
    Jack Leuba
    Director, Military and Government Sales
    Knight's Armament Company
    jleuba@knightarmco.com

    Director of Training

    FB@ Facebook.com/F2SConsultingLLC
    As accurate as needed, as fast as possible, as many times as it takes.

  5. #5
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    We get a lot of "wind" experience here....
    To say I am not good at wind drift is an understatement.

    Our "range" (the pastures "lay of the land") requires shooting WNW. Prevailing winds, this time of year, are nearly always SW to SSW- so as a rule we have full value wind most of the time.

    My wind DOPE for:

    6.5 CM 140 gr ELD-M @ 2620 FPS, 10 MPH Wind:
    100 yds = .54"/.112 MIL
    600 = 19.3"/.9 MIL

    5.56 77 gr. SMK @ 2780 FPS, 10 MPH Wind:
    100 yds. = .95"/.26 MIL
    600 = 35.5"/1.64 MIL

    BC makes a substantial difference.
    The 6.5 is a hell of a lot more forgiving in wind error at 600 than my 5.56's.
    Last edited by gaijin; 10-02-18 at 11:18.

  6. #6
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    Quote Originally Posted by Failure2Stop View Post
    Unless people spend a lot of time and effort in precisely tracking wind, they usually aren't very good at it, so that whole variable makes it hard to diagnose cause of shift.
    There's a litany of possible inputs that can cause minor shift, but 1-1.5 inches at 100 is not insignificant, and would warrant some investigation if I was seeing it in my guns.
    Copy that, but it happened with 4-6 guns. It was nuts I tell you. Just bizarre

  7. #7
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    Quote Originally Posted by Failure2Stop View Post
    With .308 175gr SMKs at 2500 at sea level (0 ft DA), each MPH of full effect wind will move the projectile .03 mils per 100 meters (roughly) out to about 600 meters, at which point it will start to increase.
    6.5mm CM 130gr AR Hybrid at 2890, each MPH of in-effect wind will move the projectile .02 mils per 100 meters out to about 700 meters.
    Wind is a thing. I could go on at length about determining/predicting wind effect, but it's really hard to effectively communicate those concepts over the internet in a short time.
    I just reread this post. Legit info thank you.

    Pretty much explains it in my opinion

    PB

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