COMPENSATING FOR WIND
with Jim See
One of the biggest challenges with accurate long range shooting is determining the correct wind hold, or how to effectively change your shot to compensate for wind. Completing this task is easier said than done. Beginner or not, determining wind direction and speed can be a challenge – but it’s an essential step in long range shooting that is important for an accurate shot. There is equipment out there that can help a shooter get closer to the bullseye, and ballistic calculating weather stations are probably the most popular – however, ballistic weather stations are expensive. Today we’ll walk through the process of determining how to edit your hold with the effects of wind speed and direction, and we’ll do it with effective, cost-efficient tools.
First, we need to determine the wind speed. While some can get an accurate estimate just by the feel, it is always important to have a wind meter for an exact wind speed measurement. I would suggest an affordable, easy to use wind meter like the Caldwell Wind Wizard II.
After determining wind speed we need to determine the direction of the wind in order to rate its value on the effect to the bullet in flight. The following wind chart shows how different wind directions affect our firing solution based on the assigned value of a wind from different clock positions. This is based on the shooter firing from the 6 o’clock position to the target at 12 o’clock.
As an example, calculate a shot at 500 yards. We come up with a speed of 12 mph, and after consulting our ballistic data, we come up with a full value correction of 1.1 mils. Next, we determine that the wind direction is coming in at 10:30 on the clock position. We can create a formula to come up with our hold.
1.1 mil wind x .71 = .781 mil wind correction
So in this example, if the wind was coming from 3 or 9 o’clock positions we would apply a correction of 1.1 mils of wind compensation. Because our wind was coming in from 10:30, we reduce the value by 29% to get a wind hold of approximately .8 mils.
Using the same example, what would our wind hold correction be for the wind at 5 o’clock or 7 o’clock? Easy – 50% of our full wind value of 12 mph, or half of 1.1 mils which would equal .55 mils. At this point, we are not worried about hundredths of a mil, so rounding it up to a .6 mil hold or down to a .5 mil hold would be fine. If you have a smartphone, you can download ballistic applications to do these calculations easily and accurately. Ballistic weather stations are also capable of these calculations, but some old fashioned math, the Caldwell Wind Wizard, and a smartphone are all just as effective.
Application in the field
You might be saying, “Wow that takes a minute to figure out! How do you apply this to conditions where the wind speed is changing up and down?”
In a competition situation, we need to find the wind high and low value over a period of time about 2-3 minutes. If we hold up our wind meter into the wind and get a speed that varies from 10 mph up to 15 mph then we may want to do the calculations for both speeds and write them down on a wrist coach (seen below). So, as we shoot the stage we can reference the low and high value and apply the correction that best fits the current condition you are about to fire in. This requires you to have an accurate “feel” for the wind and know if you are shooting in the lull (low wind) or the pick-up (high wind). Experience and being aware of your surroundings is the key to being successful and it’s why the professionals make it look so easy.
We must also remember that it is possible for the wind direction to change as well. If we were shooting in a tailwind that was switching from 5:30 to 6:30 we could miss either right or left at any given moment when holding the center of the target. Under this circumstance, we need to use every trick we have to determine the wind direction with every shot.
Mirage, the perfect wind indicator?
Mirage is a term that describes the heat waves that we can see moving in our optic when looking at a target. You can gather crucial information about wind speed and direction when studying mirage. In the head or tailwind situation, it is critical to see a mirage in determining the wind correction the second you break the trigger.
We will be able to see mirage best on days when the sun is out and there is a temperature difference from the ground to the air. A bare dirt field or moved hay field will show mirage better than a brushy hillside because the sun will be able to heat the ground better than it can heat dense green foliage. Knowing this you sometimes need to search for the best place to look.
Mirage will lie to you based on where you are seeing it and the terrain features. If you are shooting in uneven terrain with hills and gullies you may feel the prevailing wind traveling right to left, but a target up against a hillside will have mirage going left to right. This is usually caused by the wind being funneled around an obstacle, and it must be something you are aware of or it will result in a miss. It is essential to not rely solely on mirage but to also pay attention to the terrain and your surroundings at a match.
We can also determine the speed of the wind by how the mirage is flowing; the above chart is a basic illustration of that. I suggest that if you want to become familiar with the reading mirage that you go out and first practice with a spotting scope. Pick a sunny day and scan the area for a mirage. It might be easy to see coming off a road surface, a shingled roof, or bare ground. If you point your spotting scope into the wind, you will see a boil coming at you. If you pan to the right, you will see what left to right mirage looks like. Study it and in time your eye will learn to pick it up and define its direction much easier. Remember that once wind speed increase to above 12 mph mirage gets difficult to see since the air turbulence washes it away.
Other indicators of wind direction
Natural wind readers can judge many winds to within 1 mph by feel and observations. These shooters are highly in tune with their surroundings and pay attention to things such as grass movement around the target, movement of tree branches, impact dust kicked up by bullets that hit dirt and mirage. If you are a new shooter learning wind and using a wind meter, pay attention to your surroundings as the wind picks up and lets off and see the results on your wind meter. Gaining this experience will help you to better judge conditions by feel and observation.
I hope this article on the basic approach to compensating the wind and will get you started in the right direction. Follow the blog for more articles on advanced wind reading coming next time.