How much wind does it take?

Discussion in 'Long Range Hunting & Shooting' started by 86alaskan, Mar 4, 2018.

  1. Hatrick

    Hatrick Well-Known Member

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    The way I see it, the slower the bullet travels through the said distance the more moa it is moved. So as the bullet slows it is moved more. It travels in an arc to the target not a straight line.
     
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  2. Rich Coyle

    Rich Coyle Well-Known Member

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    It's everywhere for a nanosecond. If it is bumped 1/10 MOA in the first ten yards that does not get less the farther it travels. If it gets bumped another 1/10MOA in the next ten yards now it is 2/10 MOA. This 2/10 goes not become less the farther it travels. If it gets bumped a 1/10 MOA in the last ten yards before the target it will not be noticed.
     
  3. RonS

    RonS Well-Known Member

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    The variables for wind drift are force, mass and time. The force of the wind causes deflection. Deflection is the change in angle between the muzzle and the target. At 50 yards the deflection may only be 1/4 of an inch. At a 1000 yards (assuming no further deflection in either direction, as in dead air) it will be 2.5 inches given the deviation of the bullet from its intended flight early on. The sooner the deflection occurs the more the error at the end. Simple physics, an object in motion will remain in motion unless acted upon by a force. The forces here being wind, friction and gravity. The latter two cause drop, the first causes drift. A 10 mile an hour cross wind over the course of 1000 yards will deflect a 168 grain 308 bullet traveling at 2600 fps roughly 108 inches. 25-06 at 500? The ballistics calculator says that my 243 firing 115 DTAC's in a 10 mph wind will drift 9.92 inches at 500 yards. Of course there is no such thing as a consistent wind across a course and especially shot to shot. Hence the "art" of marksmanship. It's all about wind reading skills.
     
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  4. Buck Buster

    Buck Buster Well-Known Member

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    The slower the bullet is travelling the easier it is for the wind to move it, it is also easier for the wind to move a lighter bullet compared to the heavier bullets. This is why the big Burgers and other large bullets will usually be a better choice for long range shooting.
     
  5. Rich Coyle

    Rich Coyle Well-Known Member

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    If one fires a .550 BC 6.5 bullet and a .550 BC .338 bullet will the .338 bullet be less affected by the wind?
     
  6. RonS

    RonS Well-Known Member

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    Need the three variable that will affect the flight. The weight, the time in flight and the speed of the wind.
     
  7. Rich Coyle

    Rich Coyle Well-Known Member

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    RonS,

    Let's give both bullets the same time of flight and the same wind speed. While we're giving the 6.5 gets 125 grains and the .338 gets 180 grains. Now what?
     
  8. 86alaskan

    86alaskan Well-Known Member

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    Good question rich, that's something I've always wanted to know.
    On another note, shooter puts the drift I was experiencing at 4moa at 500 with an 8mph full value cross wind. So, I was at least 20in off, and maybe more because I was correcting for a light right to left wind farther down range.
     
  9. lgordee

    lgordee Well-Known Member

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    Use this free ballistics calculator and your question will be answered.
    http://www.jbmballistics.com/cgi-bin/jbmtraj_drift-5.1.cgi
     
  10. RonS

    RonS Well-Known Member

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  11. RonS

    RonS Well-Known Member

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    There is more force required to move the heavier object the same distance. In your example though, both 125 and 180 are low weights. I'd go with 140 and 300 (assuming 338 Lapua).
     
  12. Greyfox

    Greyfox Well-Known Member

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    Wind drift is about the ballistic coefficient and velocity which establishes the dwell time for the wind to drift the bullet. Weight is not the determinant. Just turns out that the heavy for caliber bullets generally have higher BC’s then the lighter bullets. A 300gr bullet from a 338 Lapua and a 140gr in a 6.5 Creedmoor, both staring out at 2800 FPS with identical BC’s will have comparable wind drift characteristics. I have experienced this with my shooting out 1000+ yards in a constant speed/direction of wind.

    IMO, without sophisticated methods, it is virtually impossible to predict the exact effect of the wind for a given shot, particularly at the longer ranges. Lots of practice makes you better, but not perfect. I found an excellent practice method is shooting my precision 22LR from 50-300 yards. I shoot all year round going through several ‘bricks” of ammo with the particular goal of learning how to more accurately determine wind. My 22LR behaves very similarly to my centerfire with drop and wind drift calculations, accurately determined by a ballistic calculator. If you establish an accurate velocity and BC for the 22RF, it works perfectly in a ballistic rangefinder out to 300-400 yards. The difference is “range” scale. My rimfire at 200 yards with 10mph, 3’clock, wind has the same 6.5 MOA wind drift(and .5MOA accuracy), as my 6.5x47 Lapua at 1200 yards. I routinely practice first shot hits on a golf ball the my 22 rimfire at 200 yards in “all” sorts of wind conditions..........it really helps with wind reading skills, which are transferable to LR centerfire work.
    BDC8309F-215D-4666-A661-F6D325258F40.jpeg
     
    Last edited: Mar 25, 2018
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  13. graywolf

    graywolf Well-Known Member

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    Seems that there is a lot of confusion about the difference between angular deflection and lateral displacement (drift). A bullet that leaves the barrel travelling North and encounters a brief pulse of East wind will be laterally displaced but still travelling North when it gets back into still air.
     
  14. RonS

    RonS Well-Known Member

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    Actually it is basic physics. Assuming all being equal except weight, more force is required to move the heavier object the same distance. Of course all things are never equal but that was the proposition.