Wind impacts the horizontal plane along the bullet flight path while air density and gravity impacts elevation. In rare topographic cases wind may impact the vertical plane such as when shooting up into a narrow canyon. The first step is to determine the wind direction; the angle of the wind to the path of the bullet will either have a major impact on the travel of the bullet or a minor impact depending on its speed and wind direction. The origin or angle of the wind is expressed in “values.” A full value wind is a 90-degree wind blowing either ‘right to left’ or ‘left to right’ from the shooting position of the rifleman to the target. A half value wind blowing at 45 degrees has half the impact on a bullet than a full value wind, and a 30-degree wind has a third of the value of a full impact wind. As an example, if you have a 10 mph wind blowing across the range of fire at 90 degrees, the windage adjustment will be greater than the same speed wind from a 45or 30-degree direction. If you have a 10 MPH full value wind and a range of 500 yards the bullet will push off course by 18 inches and the adjustment needed is about 3.4 MOA for a 175 grain bullet while a half value wind will only blow the bullet off course by 9 inches and the MOA adjustment is 1.7
There are three basic ways to determine speed and direction, without the expense of a handheld weather station:
1. The way the wind is causing foliage to move.
2. The direction and angle of the flags on the shooting range.
3. By reading the wave patterns contain in a mirage.
Ralph Troy Hicks is the author of Fundamentals of Long Distance Shooting and Fundamentals of Long Distance Shooting II. He is a competitive shooter who set out to design and manufacture the finest semi-auto in the world—a rifle that could hit a dime at 100 yards and reach out to 1,400 yards with minimal felt recoil. It took over three years to develop this firearm. His goal was to take the precision of a bolt-action rifle and the speed of a semi-auto and marry them together in a stunningly beautiful firearm platform. It has the power, speed and precision to make any shooter into a champion.