Tail wind effect at 1,000 yards?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Len Backus, Oct 20, 2003.

  1. Len Backus

    Len Backus Administrator Staff Member

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    Muzzle velocity of 3,150
    BC of .750
    Tail wind of 10 MPH

    How much (in inches) is the point of impact affected at 1,000 yards, please?

    Come on, you guys, who shoot thousands of rounds per year in long range competion. Help out someone who is a rank beginner at that range.

    [ 10-20-2003: Message edited by: Len Backus ]
     

  2. dbhostler

    dbhostler Well-Known Member

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    Forgive me for speaking out of turn. I have shot at 1k and am by no means even a fair judge of wind, but the "old timers" I have spoken with at the range don't like the wind behind them. I guess if the wind is one side of your face or the other, even out to 1k, you can tell when to shoot and where to hold. But if it's blowing from behind, they tell me you don't know what it's going to do. This is in prone 1k shooting. I would guess BR is a little different.
    db
     

  3. 700

    700 Well-Known Member

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    Len

    I get 0.92 inches high for a 10 MPH tail wind at 1000 Yards. Compare this to 4.5 inches at 1000yards for the .308 BlackHills matchKing loading. I guess you have that tail wind thing licked.

    Will I email you the chart at your profile email address.

    Regards

    700
     
  4. Len Backus

    Len Backus Administrator Staff Member

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    700

    An answer from Ireland! Small world, isn't it?

    Which ballistics program are you using that offers that option?

    Thanks.
     
  5. Darryl Cassel

    Darryl Cassel Well-Known Member

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    Len

    With that high of BC and the Velocity your running it, a 10 mile per hour tail wind will only move you 1" to 2" if that.
    Not a major concern if the wind stays constant and you had a spotter round or sighter period to watch what happens to the bullet.
    That's only one click from a 1/8th MOA scope or 1 1/4" impact change at 1000 yards.

    Not really that much to worry about if your Longrange hunting at 1000 yards.

    Later
    DC [​IMG]
     
  6. 700

    700 Well-Known Member

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    Len

    I have read your "Optics For The Hunter" book. I guess that makes it an even smaller world. Great book. Very informative.

    I have software written that does all this for the .308 175 Gr. Match King Loading. All I had to do was change the BC and Muzzle Velocity.

    Email to follow in a few minutes.

    Regards

    700
     
  7. Len Backus

    Len Backus Administrator Staff Member

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    Thanks, DB, Darryl and 700

    Dave Tooley yesterday told me how to get the answer from the ballistics program I use...Oehler's Ballistic Explorer. I just never knew where to look. Its answer agrees with your suggestions.
     
  8. Brent

    Brent Well-Known Member

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    Len,

    I'm not sure when you got your Oehler BEX program, but Dexadine has an update release for it, although I'm not sure what they did on it, mine looks the same after updating it.

    It's at www.handload.com

    What was the solution you found?
     
  9. Len Backus

    Len Backus Administrator Staff Member

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    Brent

    Thanks, I hadn't upgraded my 8 year old version of BEX for a few years. Can't say I see what the difference is so far.

    Solution is less than one inch. Not something I'll be a able to blame my poor shooting on! [​IMG]
     
  10. MAX

    MAX Well-Known Member

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    Darn the luck! [​IMG]
     
  11. speedbump

    speedbump Well-Known Member

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    Len,

    That number's probably pretty close from what I've experienced. HOWEVER, you'll want to watch for a vertical 'updraft' push from a tail wind blowing up slope(s) downrange.
    You can usually see weeds flattening against hillsides downrange. Unless you catch the effect, it causes a change alot like a sudden boil - out the top!

    BC of .750 at 3,150 huh? Sounds like your stuffin' some 7mm Cauterucios....???????
     
  12. Len Backus

    Len Backus Administrator Staff Member

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    Yup! Just determined today, though, that my 9 twist barrel just isn't cutting it with them though.
     
  13. speedbump

    speedbump Well-Known Member

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    Boy, that's a shame. A nine twist is what I have in the 7RUM, & it works pretty well at @3,400. Have you tried the 156s yet?
     
  14. Len Backus

    Len Backus Administrator Staff Member

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    I'll order some 156's from Bob today and see how I do. I have a new barrel ordered for delivery around January one. Haven't decided whether it will be another 7 Dakota or a bigger seven. Are you satisfied with your RUM? Case quality ok? How many firings each? How long is your barrel to get 3400 with the 176's? What is your load? Group size?

    If I go with a bigger seven should I stick with the 9 twist as you say yours works? Or if you had your choice would you go with an 8?

    [ 10-26-2003: Message edited by: Len Backus ]