How To Read The Wind – The Ultimate Guide – 5

In Blog by Rich2 Comments

So here we are, the last in the series of articles on How To Read The Wind – The Ultimate Guide! Part 5 of this series is going to be all about putting what we discussed in prior installments together. I’m going to stress again, there are many methods for reading the wind. Some worse, probably some better than what I’m describing here. This is just how I do it! It may help some newer or lesser experienced shooters and that’s why I’m tossing it up here. I didn’t learn this anywhere and I’m not regurgitating anything I’ve heard elsewhere, this is what I’ve developed as my own method as I’ve learned to be a better shot at distance.

Reading the Wind

If I’m heading out to shoot, my wind reading starts on the drive to the range or match or wherever I plan to shoot. As I’m driving to my shooting position, I’m already looking at what’s going on during the drive out. Look at the angle that the mirage is running off the highway in front of your car. What’s going on with the trees on the side of the highway or road? What about vegetation? Is the grass blowing around wildly or hardly at all. Start taking it all in before you even get to where you plan to shoot. You already need to be in a loose mindset of “its a calm day” or “man it’s really blowing” before you arrive. Keep paying attention as you get set up at your shooting position.

The first thing I look at when I’ve arrived at the spot I plan to shoot from is the angle. Where is the wind coming from and at what angle in relation to my direction of fire? This is where the information in previous segments regarding wind clocks and the value of wind based on its angle come into play. The reason I start with the angle is simple…its easier to work with larger numbers. If you run your wind calculations based off of a 10mph Full Value Wind, like you should be, its easy to run the angle against your dope. The wind corrections for 10mph are bigger than those for say 5mph or 3mph. So do the wind angle adjustment first, then change it to match the speed.

millett-clock

This is overly simple, but don’t get crazy with values, generally I find that Full Value-3/4 Value-1/2 Value-No Value is as complicated as you need to make it

Example 1

For example, my match gun’s wind compensation for 500yds with a 10mph Full Value Wind is 0.7 MILs. Let’s say the angle is 3/4 Value at my shooting position. I could try to do 0.75×0.7 in my head, but that’s tough math. 0.8 is a rounder number, and easier to work with. If 0.8/4 is 0.2, then the mental math value for a 3/4 Value 10mph Wind at 500yds is 0.6 MILs. I know that’s going to be a touch high since I rounded up for easy math, so I would hold just under 0.6 MILs. Incidentally, the calculator answer is 0.525 MILs. So we’re pretty close with mental math. In fact, we’re within 0.075 MILs! Or in real world distance, the mental calculation gets us within 1.35″ at 500 yards. Most people can’t even group rounds into a circle that small at that distance, so we’re within an acceptable range of error.

What about the speed? Well, let’s say its a 4mph wind. If we were working with 0.6 MILs after the angle adjustment, we need to adjust again for speed. 4mph is what percentage of 10mph? 40%, right? So we can try and do 0.6*0.4 in our head. Or do some mental math again and think to ourself, “Self…40% is pretty close to 50% and 50% is a much easier number to work with!” So 50% of 0.6 MILs is 0.3 MILs. Again, we know that’s going to be a touch on the high side because we’re rounding numbers to keep things easy and quick so we can do this kind of math quickly in our head. I’d be holding slightly less than 0.3 MILs, I’d call it a 1/4 MIL hold. What’s the mathematically perfect answer? 0.24 MILs.

So we adapted the original hold for 500 yards of 0.7, an odd number, for angle and speed and we’re within 0.01 MILs of the calculator answer. How’s that for keeping it simple? My ballistics calculator says the answer for the match rounds is 0.1 MILs. So we’re off by less than 2″ at 500 yards without a calculator. The ballistics software also tells me that at 550 yards, the hold becomes 0.2 MILs, so we’re pretty close to the range where our mental ┬ámath calculation would be even closer. Let’s try another example.

Example 2

Lets say we’re working with a 825yd target, a 12mph wind from about 11 O’ Clock. I check my ballistics table, or my calculator, and see that my 10mph Full Value Wind is 1.2 MILs. Angle first, remember? 11 O’ Clock is roughly a half value wind so 1.2/2 and we get 0.6 MILs. We’re also at 12mph, a 20% increase over the 10mph hold. 0.6/10 is 0.06 and 0.06×2 would be 0.12, or 20% of 0.6 MILs. So roughly a tenth of a MIL. So for my speed corrected hold, I’d hold 0.72 MILS, which is pretty close to 0.75 so I would probably just go with a three quarter MIL hold and go for it. My applied ballistics software says the correct hold is 0.7 MILs. So even favoring a little strong with 0.75 we’re within 0.05 MILs at 825yds. Less than 1.5″…at 825 yards.

A 1 MOA target at that range is on the small side, and our mental math would be off less than 25% of the size of the target. The best part about doing things this way is that it’s easy math. It’s not dependent on constants or adding .1 MIL every 100 yards after 600 or whatever. This keeps things fairly simple and quick and easy to do in your head. Here’s a huge point to remember…I’m not saying there’s anything wrong with using a ballistics calculator! If you have the time and opportunity to sit there and plug in the actual wind angle and speed and wait on the result, go for it! This is just my version of Field Math that works for me. I took two examples and showed you how I would do it mentally, by looking at my 10mph Full Value Wind for that distance and came up with an answer pretty close to the textbook answer provided by software. Will it work for you? I don’t know…try it!

Wrapping Up

Again, if time and opportunity make it possible…let the computer do the math and use the mathemagically perfect firing solution. On the other hand, in a dynamic environment, maybe you have to contend with targets that are only exposed for limited time. Maybe you are being timed in a competition. Maybe you’re being shot at by the target. Whatever the reason, if you don’t have the time to pull out the computer and plug it all in, you can look at a chart for half a second and use my version of Field Math to get an answer that’s going to be pretty damn close, and a hell of a lot faster than plugging stuff into the computer.

aa target

Remember, the objective is to hit something like this, quickly, in field conditions without sighting shots or warm up ammo…keep the math simple so you can do it in your head, you only need to be close enough to hit it!

I didn’t read this in a book, this is just how trial and error has taught me to do it. I’ve tried plugging every target range, angle, and wind speed in before stages at competition…it’s tedious and it’s not much fun. Know what else? It’s useless. The wind can change angle and speed in less time than it takes you to find the firing solution for one target using a computer. This is a quick way to adapt, on the fly, using simple math that you don’t have to be a trigonometry expert to do in your head. Give this a try, and please ask questions or tell me how it works out for you in the comments below!

Owner and Proprietor of AccuracyTech, LLC. Rich is a Firearms Enthusiast, Precision Rifle Competitor, and Writer. He is committed to bringing readers quality reviews and articles related to the Precision Shooting Sports. If you have any questions for him, please use the contact form on the site.

Comments

  1. Really enjoyed this article but I do have one question being a newbie to long range shooting. How do I come up with the 10 MPH Full Value baseline to begin with? I’m assuming I just plug the data into a ballistic calculator then print off the table and set it for a 10 MPH Full value wind?

    1. Author

      Correct, James! Plug in your data into whatever ballistics calculator you are using and set the wind angle to 90 degrees or 180, 9 O’ Clock or 3 O’ Clock, however it asks. Set the speed to 10mph then use that as your baseline!

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