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9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

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  #1  
Unread 02-10-2012, 06:02 PM
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9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

I'm getting 52" of drift with a 9 o'clock vs. 33" of drift with a 3 o'clock wind using bullet flight on my iPhone. I'm assuming these numbers are different due to spin drift with a right hand twist but didn't think the difference would be that great. Am I doing something wrong? This was a 5mph wind @ 1000yds.
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  •   #2  
    Unread 02-10-2012, 06:24 PM
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    Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

    Not sure why you're getting that. I get the same going either way on mine, only difference is -2moa or 2moa depending in wind position. I'm using bullet flight fte on my ipod
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    Unread 02-10-2012, 06:28 PM
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    Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

    Something is wrong. Probably an input parimeter or a lead installed like a moving target app. Spin drift at 1000 should be more like 5 to 7 inches. Go over all your settingand see if one needs zeroed out.

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    Unread 02-10-2012, 08:21 PM
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    Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

    52-33=19
    divide by 2 = 9.5"

    Seems a bit much for Spin drift even with Coriolis thrown in as well. But I just punched the numbers into "Shooter" for a .308 with 155gn bullet and they are similar for a Northern Hemisphere location when SD and CE are taken into account.
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    Unread 02-10-2012, 09:23 PM
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    Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

    Both spin drift and coriolis are being accounted for. Also this was 180gr. Fusion ammo B.C.=.478 going 2950
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    Unread 02-10-2012, 11:37 PM
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    Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

    Another interesting fact is that 52" of drift @ 5mph becomes 94" when 10mph is plugged in. I would think it would be 104". Ive gone through this app and can't find what could be causing these readings. If I take spin drift off and coriolis off then the drift is the same whether it be a 3 o'clock or a 9 o'clock. It does make sense that with a no wind hold the bullet would drift right (and low) with a right hand twist so I could understand a different hold when dealing with a 90* or a 270* wind. I just have a hard time believing it would be as great as what it is telling me.
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    Unread 02-10-2012, 11:59 PM
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    Re: 9 o'clock vs. 3 o'clock wind drifts different with same wind velocity???

    Quote:
    Originally Posted by shortpants View Post
    Another interesting fact is that 52" of drift @ 5mph becomes 94" when 10mph is plugged in. I would think it would be 104". Ive gone through this app and can't find what could be causing these readings. If I take spin drift off and coriolis off then the drift is the same whether it be a 3 o'clock or a 9 o'clock. It does make sense that with a no wind hold the bullet would drift right (and low) with a right hand twist so I could understand a different hold when dealing with a 90* or a 270* wind. I just have a hard time believing it would be as great as what it is telling me.
    That does seem excessive. The numbers I've seen generated from Exbal suggest only a 3" effect at 1000 yds due to Coriolis alone. Spin Drift (as near as I've been able to gather) could perhaps be 3 times that amount in some cases.?.........Still, we're only talking about maybe 12" difference at 1000 yds, not 19".

    Every app that I've personally looked at also suggests that a 10 mph wind doubles the effect of a 5 mph wind. Hmmmn.....??
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