# Vertical drift from crosswinds

Discussion in 'Long Range Hunting & Shooting' started by Oli, May 7, 2003.

1. ### OliMember

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I've tried to get info about this in many other forums, but noone seems to be able to give me any concrete advice.

There is quite a lot of literature written on the topic, I know that. But I'm not willing to spend 50\$ for that info only. Now I'm asking you people, that apparently do quite a lot of shooting at long ranges. How do I estimate the vertical drift component of crosswinds?

[ 05-07-2003: Message edited by: Oli ]

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3. ### Michael EicheleWell-Known Member

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Do you meen horizontal drift from cross winds or verticle drift from head winds??

I have lot of math for crosswinds. But I dont have any math on head winds.

4. ### OliMember

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Excellent! Thanks Brent!

Neither of them, Michael. Vertical drift from crosswinds.

[ 05-08-2003: Message edited by: Oli ]

5. ### MysticplayerWriters Guild

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Oli, the only way that a crosswind can impose a vertical component is if the wind is flowing upwards (thermal) or downwards (wind shear). These are usually not something that happens to any large degree over most flat ranges.

If you are shooting in the mountains or over/near valleys, you will have to use wind flags and learn through experience. The math is way too complicated because you have so many possible vectors.

For windage, both side and head/tail, the affect is treated as a single variable leading to a single adjustment. Quartering winds rising or falling or swirling would probably need a NASA engineer to guess at.

Best advice is to practise. Each cal/cartridge/bullet/barrel has its own special characteristics and real world shooting will give you more info then any computer modeling. Too many variables to compute. Plus the info inputed would not be complete or accurate for a different range.

This is not a cope out, just a fact. As a rule, we don't give crosswinds any vertical stringing component. Vertical stringing comes from head/tail winds, poor loads, poor recoil control, and /or boiling mirage.

Jerry

6. ### OliMember

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<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>This is not a cope out, just a fact. As a rule, we don't give crosswinds any vertical stringing component. Vertical stringing comes from head/tail winds, poor loads, poor recoil control, and /or boiling mirage.

Jerry
<HR></BLOCKQUOTE>

It's not really vertically stringed groups I'm talking about. That's a completely different story.

I've seen some tendencies to the vertical-drift-from-crosswind phenomenon. It is of course no conclusion I've done from analysing one wind drifted round only. As you know, there are way too may other factors that can explain one drifted round. But there seems to be a tendency for it when looking at many groups shot in crosswinds. There are however no greater differences and I would definately not worry about in hunting situations. Nevertheless, it's an interesting phenomenon that has drawn my attention away from far more important things for some time now.

Now I have finally got my hands on these precious pages from Vaughn that have become almost mythical (is that a word?) by now. So don't ruin my fun .

Even though it seems hard to predict the vertical component, I'm looking forward to read more about it. Hopefully, I will become better at analysing groups. At least there will be one more factor to blame

[ 05-08-2003: Message edited by: Oli ]

7. ### BrentWell-Known Member

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Oli,
the rest of the book is just as good and better too, well worth the money. I'm sure you have the basic idea from that part though.

8. ### STL_ShooterWell-Known Member

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Oli, I'll second Brent's advice and suggest you read Harold Vaughn's book. You won't go astray with Harold at your side.

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[ 07-11-2003: Message edited by: S1 ]

10. ### MAXWell-Known Member

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As I recall, Vaughn implies that without going into great detail. Robert McCoy goes into it in more detail than I can understand after one read, but the mathematical formulas are included for all aspiring rocket scientists. It is a small value thing, perhaps on the order of Spin Drift calculation which is also proportional to GS. His book is "Modern Exterior Ballistics", available from Amazon.Com for about \$95.00.