Intro to Wind Reading and Mirage
Whispers fly back and forth. “What do you think it’s worth? Quarter, maybe half.” The reactions vary up and down the firing line. Some shooters sit relaxed in a folding chair, waiting for their relay to be called, seemingly unconcerned. Others set up their spotting scopes behind the line, looking between the spotting scope and the wind flags – back and forth, back and forth. Blades of grass thrown in the air like confetti drift through the air. For mid and long-range shooters, wind is a hot topic. Everyone likes to complain about it, few understand it, and almost everyone has blamed a few bad shots on it.
Environmental factors have a significant impact on bullet trajectory. Wind is the primary factor, and its effects on a shot increase with the distance the shot is fired from. Think of it like a kite on a windy day. The more string you release, the further away the kite is, the further it drifts and is caught by the wind. Wind will essentially “push” your shot to the right or left of where you desire it to go. (Technically it can push it up or down, but this is a more complicated discussion.)
There are two main ways to compensate for wind drift on the line: holding over or adjusting sights. Holding over or favoring one side of the target over another can work well when hitting a target anywhere is the main goal, not in one particular spot. In most cases, it is better to move the sights to adjust for the wind than to just “favor.”
Favoring is changing your sight picture so that your aim point is different. Picture a clock face. You want your shot to land at the center of the clock, but the wind is pushing your shot to 9 o’clock. By aiming at the 3 o’clock mark rather than the center, theoretically the wind will blow your bullet into the center. This method is far from precise as it is difficult to judge exactly how much to change your sight picture. Also, so much time is spent on developing good sight alignment and sight picture that changing it up can distract you on future shots. It is best to keep everything the same.
Adjusting your sights is much more precise. It changes the point of impact without changing the sight picture. (Keep in mind you will need to adjust your sights with every wind change.) The real question is, how much do you move them? Learning to read wind and read mirage is a lifelong skill, and you are always wrong at one time or another. There are various charts available as well as devices that can help you determine the wind speed and direction.
In some forms of competition, you are allowed to have electronic wind readers which eliminates much of the guessing game, in others, you must reference wind flags. Wind flags are pieces of fabric hung at various distances from the shooter to the target. They indicate what the wind is doing at that location, but the flags can “lie.” Sometimes multiple flags will be going different directions. Other times, the point of impact seems the opposite of what the flags indicate. First check to make sure you turned your windage knob the correct way. Everyone makes this embarrassing mistake at one time or another. Wind behavior (speed, direction) changes with the landscape (valleys, hills, etc.) and is often not consistent the entire way from the rifle muzzle to the target.
Reading mirage is another useful tool. Traditionally, mirage is best observed through a spotting scope. (If you can see mirage through your rifle scope, it is likely not in focus on the target.) Adjust the focus until the target is crisp and clear, then turn the focus counter-clockwise until the image is just blurry. The “waves” you see is mirage, a result of light refracting, that gives you an overall indication of what the wind is doing. Mirage is not always visible. It depends on warm temperatures and you generally won’t see it when winds are over 12 miles per hour. If the wavy lines are moving right to left, then the wind is moving the bullet to the left, so you need to move your sights to the right. If the wavy lines are moving left to right, then the wind is moving the bullet to the right, so you need to move your sights to the left. If the lines appear to be rising straight up, this is called a boil. Do not shoot in a boil unless you absolutely have to (and as long as it is safe). A boil disrupts the target image and makes it appear that the target is in a different spot than it actually is, an optical illusion that will negatively change your point of impact.
Mirage not only helps estimate the general direction, but wind speed. The faster the waves of the mirage appear to be moving, the faster the wind. There are many charts, books, and videos about wind reading, but the best teacher is experience. I will never pretend to be an expert, but the charts only tell you so much. Over time, reading mirage and reading wind becomes sort of automatic, given of course, you have an understanding of the ballistics of the bullet and caliber you are shooting. Different calibers and different loads for those calibers react differently to the wind. For example, a 10-mph wind will move a .223 bullet more than it will a .308 bullet. (Think of trying to push over a plastic table versus a metal one.) Some calibers have been developed specifically with aerodynamics in mind.
Highly simplified, your goal is to determine the speed and direction of the wind. Meters can help with this as well as various charts and apps that cross reference the speed and direction with the distance, caliber, and bullet you are shooting to provide an estimate of the amount you need to move your sights. When taking multiple shots on a single stationary target, your goal should be a waterline. This means that all of your shots are in a line across the target. If they are to the left or right of center, but have good elevation, this means that if you had estimated the wind correctly, you would have had a perfect shot.