Wind effect

[bgary]

I recently saw a "sniper" windage card that had a sort of clock-face diagram for showing the effects of wind on bullet impact. It indicated, for example, that a headwind (12:00) would cause the bullet to impact low, and a tail-wind (6:00) would cause the bullet to impact high. No problem.

But it showed that full-value cross winds would have *different* effects on bullet impact, depending on direction:

-- a full-value cross-wind from right to left would cause bullet to move left and high

-- a full-value cross-wind from left to right would cause bullet to move right and low

I couldn't model this in the JBM calculator - whether the wind was at 90-degrees or 270 degrees, it produced the same drop-values at every distance.

It got me wondering, though... I can imagine this is due to spin, and dependent on whether the rifling is right-hand twist or left-hand twist.

Anyone experience this? Is it a "real" thing, or a non-issue at distances inside 1000?

[Skydiver]

As I recall, for .22 it does make a difference between left or right crosswind. I just can't recall at what distance in started to matter, though.

[Graham Smith]

I'm familiar with that. Somewhere in the back of my head is a voice saying it came from the Canadians, but...

In any case, there's a lot of things that will effect the bullet path. The interaction of the wind and the spin is one but is generally negligible, just as Coriolis effect is.

Of greater importance is the fact that wind speed is not consistent. I may be stronger or weaker or different direction between you and the target. Generally speaking, wind will have a greater effect at the shooters position than at the target because a small deviation at 10yds can translate into a much greater deviation at 800yds.

As to JBM, I'm pretty sure that wind calculations only effect the windage numbers rather than the drop.

[dkleskiw]

The combination of your bullet weight and velocity tolerances will have more of an effect than the Magnus Forces will.

[Nowind0]

I have shot a lot of long range highpower matches, and I have never adjusted for the wind effects on elevation save on certain ranges, a head wind will cause an updraft when it hits a lesser yardage firing line berm, and will make your shot go high.

I do not think you need to worry with it. I seriously doubt it is worth more that 1/4 MOA. Like DKLESKIW said, variances in your components, powder charge, seating depth, and even head position on the rifle will cause more effect on your shot.

[Biloxi23]

when you shoot rigles at distances of 1,000 yards and greater, there are lots of things that will make you bullet impact higher or lower. Here in south Mississippi in August, the heat can greatly effect where your bulloet hits in relation to your normal zero. Humidity, sunlight, wind and the rotation of the earth all effect teh flight of a miving, spining projectile as will teh uniformity of the projectile itself. You can buy all of the ballistic charts, ballistic computersand other doodads you want (I have most of them) but there is no better way to detrerming what you rifle/bullet combination will do than to shoot it in those conditions. That's why long range shooters are so anal about their data books. Some long range shooters are even starting to use video to record their data, shooting and the conditions.

[JKSNIPER]

Jakers...a LOT of data books and so called "instructional " books have stuff in them that is just flat out wrong.

Theres stuff out there telling guys that temp fluctuations of 20 degrees will cause 1MOA difference in POI....bullpoopy.

You start making adjustments off that book and you'll miss a whole lot of stuff.

Fullvalue wind refers to wind that is perpendicular to the path of the projectile.

A ballpark calc to guesstimate windage is this:

1. Range expressed in hundreds of yards

2. Times wind expressed in MPH

3. DIvided by the constant of 15 for a .308 rifle or 10 for a .223

4. Answer is in MOA adjustment for you .

For Example:

Lets say we're shooting at 300 yards and its a 20 mph wind full value from left to right.

3 times 20 equals 60 which we then divide by 15 to get 4 (MOA) . ( 3 is the range expressed in hundreds of yards. 20 is the wind at 20mph and 15 is the constant we use for a .308 rifle)

I am going to be 4 MOA right if I shoot without adjustment.

1 MOA at 300 yards is 3". 4 MOA equals 12 inches.

I need to "hold off" 12" left OR make an adjustment to my sights.

If the wind is half value? Divide the answer by 2.

Quarter value? Divide your answer by 4.

HOWEVER...there is NO substitute for actually going outside and shooting in various wind conditions to see just how much of a PITA trying to keep up with mother nature can be.

Wind is rarely constant here on Long Island....we have gusts then lulls in the wind.

If you figure out the max gust for an adjustment and then shoot during a lull...you're going to be very pissed off at the result.

Sometimes the best shooters don't mess with the wind...they watch it and see a pattern and then try to adapt to it.

Gunny Hathcock won the Wimbledon cup one year by waiting for the wind to die down and THEN shooting during the lull period.

[Biloxi23]

By data books, I was referring to each shooters recorded data of how his rifle shjoots in a particular condition, and not a generic "how to" book. I shoot my rifle a lot an experience lets me know what it will do because I've done it before. son't spend a lot of money on teh "doodads" just spend the money on ammo and shoot.

[JKSNIPER]

Biloxi23 I meant that a lot of data books contain info on windage and elevation and other things that is simply wrong....not that your personal shooting info is wrong and if I was not clear on that I apologize.

[Biloxi23]

Biloxi23 I meant that a lot of data books contain info on windage and elevation and other things that is simply wrong....not that your personal shooting info is wrong and if I was not clear on that I apologize.

Cool. Maybe I wasn't so clear on the data book line. You are right, and there are a lot of companies that have discovered the "sniper" craze that seems so prevalent now. A good part of the "doo dads" main function is to separate shooters from their money. At my local range there are a bunch of guys that have tricked out, 1,000 yard rifles that can't hold 3" at 100 yards. The most awsome shooter I ever met shot an old Savage heavy barrel in .30-06. He was about 80, had been shooting for 70 years, and he could not just read the wind, I think he could see the wind. Over the course of one year he taught me more about shooting than I ever acquired any where.

[JKSNIPER]

Then to make things even more complicated........

We have the multiple wind situation.

If you shoot enough high-power rifle on full size ranges eventually you'll probably see wind at the 200 yard line going left to right...wind at the 300 going right to left....and at the 600 blowing straight down the range from up range to down range.

Look at the target...focus your scope on the target then take it about a quarter turn out of focus....this will enable you to see the "mirage" effect of heat waves boiling up off the stuff around your target. I can usually find it down on the berm in front of my target.

It gives the last wind condition to affect your round prior to striking the target.

JK

[Biloxi23]

Or if the range is narrow, with fairly high berms (like the one I shoot at, it narrows way out), them wind will swirl. You can see it through the optics, and it looks like a miniature tornado. At about 275+ there is a low spot in teh berm on one side and this will sometimes cause the wind to push the bullet from the opposite direction from the prevailing wind. There are so many variable, it sometimes becomes more of an art than a science. Then Yu sometimes have days where teh conditions are terrible and you can't seem to make an experienced judgment on any of the factors, and despite this you still seem to be able to get good hits. I

[JKSNIPER]

On MOST ranges there is a "favorable" side to be on.

Usually shielded by trees or a berm from wind that the rest of the range is experiencing.

You can have a 4 MOA full value wind at position 25 and at position 1 have 0 wind.

Thats why to shoot in the wind you have to actually get outside and SHOOT IN THE WIND to learn how to do it.

JK

[JKSNIPER]

and if you're at a high-power match and you overhear a team coach giving corrections on the wind to his shooters make sure you think for yourself prior to doing anything.

The joke goes:

New shooter on the line ask an old timer what he used for wind correction and the shooter answers "I used 10" right."

The new shooter goes up to the line and fires.

He comes back off the line saying : " That was horrible! I think thats the worst I've eve shot...I thought you said to use 10" right to correct for the wind."

The old timer says "I did use 10" right....and my shots were 10" right".

Also there are coaches that will give out a correction in a loud voice hoping people will hear it and then give the "true" correction to his shooters in a much more subdued tone of voice.

You can see the new guys frantically twisting their sights this way and that while the vets shake their heads and smile.

JK

[Ben-Sons]

Thats why to shoot in the wind you have to actually get outside and SHOOT IN THE WIND to learn how to do it.

JK

Agreed! The same as gathering data, no cards or programs will tell you where YOUR round will hit.

My theory on any new information is, go prove or disprove it on the range.