Windage Compensation

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    Windage Compensation

    By Jack Peterson, Producer of Best of the West TV Show

    Anyone that has spent much time in Wyoming knows that the wind can really blow here. According to the University of Wyoming’s website at www.uwyo.edu, “Wyoming contains over 50% of the United States’ top categories for wind energy resource”. Whether it’s the plains of eastern and southern Wyoming or the mountain valleys and peaks of the western Rockies, the wind can be a factor for hunters on any given day of the year. As the birth place of Huskemaw Optics, Wyoming has been the premier place to develop rifle scope technology and to put our scopes through the most rigorous field tests. From wind drifted roads and trails, to wind-proof tents and clothing for hunters, wind is a reality that must be dealt with on many different levels. In this article, we will cover some of the effects wind has on the flight path of a bullet and what can be done for both minimization and compensation.

    The truth is it doesn’t take much of a wind to have a significant affect on a bullet.

    Diagram A is ballistic data for a Nosler Partition example round. This bullet was developed decades ago and has remained the standard for comparison to other bullets. It has been known for both its superior penetration and bullet weight retention characteristics. A good 30-300 yard bullet, however, not a great long range bullet choice.

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    You will notice that with a 200 yard zero and with a 10mph full value crosswind, there is already 5.9 inches of wind deflection at 300yds. At 400yds and with almost a foot of deflection, this could put the bullet completely out of a kill zone. Of course, this is depending on the size of the animal and the angle and position it is in. If we look at the 1000 yard information in the diagram, we have over 85 inches of deflection, and at this distance the bullet could wind up in the next county. This tells us that in a stiff to strong wind and with a low BC bullet, if we do not have a way to know how much wind we are dealing with, we really can’t shoot ethically past 300 yards.

    Now many of you have watched us on our “Best of the West” TV shows and videos shooting successfully at very long ranges and sometimes in higher wind situations. It is imperative that you understand that in each of these scenarios we did know what the wind value was before we took the shot. We also had a way to hold these values using the hash marks on the horizontal line of the Huskemaw “huntsmart” reticle.

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    Notice the hash marks on the HO reticle design in this picture. There are 8 total hash marks on each side of the center cross hair. Each mark is 1 MOA apart at the scope’s full power. With this design if a user needs to hold 5 MOA they instantly know it is one hash mark past the tallest 4 MOA hash. With many reticle designs it is necessary to count each hash mark and concentrate on the correct one, so as not to lose track and have to recount. When you are in a hurry shooting at a changing target, this can make all the difference of a hit or a miss.

    Obviously making these kinds of shots are not as simple as I just explained. I will try and demonstrate some of the things we can do to minimize wind deflection.

    The first thing we can do to improve our ability to shoot in windy conditions and at longer ranges starts with bullet selection. Like range finders and scope technology, bullet designs have evolved over the past couple of decades. With our advanced understanding of aerodynamics, engineers have been able to apply better and more efficient designs to all kinds of products. Our airplanes, boats and vehicles are all much more streamlined than in the decades before. The same can be said for bullet designs. Long range bullets are designed for flatter trajectories and this increases their ability to resist some of the effects of the wind. Below is the design features of Hornady’s new ELD-X, Extremely Low Drag-expanding bullet.

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    Heat Shield Tip
    Defies the effects of aerodynamic heating,
    retains its shape and maintains BC over its entire trajectory.
    Match accurate hunting bullet
    Streamlined secant ogive with optimum
    boattail design
    Devastating conventional range performance
    With high velocity, 0-400-yard impact, the bullet continually expands throughout its
    penetration path.
    The thick shank of the jacket and high Interlock ring keep the core and jacket together.

    If we go back to our Nosler Partition example and compare it to Hornady’s new ELD-X bullets, we can get a good idea of the kind of advancement there is in today’s bullet designs. (See graph B). In addition to nearly double the delivered energy at 1000 yards, the wind deflection is amazingly lower. What does this mean? At the end of the day it means there is a much greater advantage for error when calculating the wind with a higher BC bullet than with lower BC bullets. It also means much higher retained velocities, flatter trajectories, and better bullet penetration and expansion. All of these factors result in much better terminal performance at longer ranges.

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    So choosing a higher ballistic coefficient bullet is the first place to start as you consider wind compensation. You may have to try more than one bullet and maybe experiment with different brands of bullets to find what your rifle likes the best. Another option would be to look at purchasing a turnkey long range shooting system that is already set up ready to go.

    Ballistics programs like the one I am using here from Huskemaw Optics will give you wind hold data for the distances you will be shooting. In the ballistic charts A and B, I have selected the wind value output in inches. When running data for taking to the field, we always select the wind value to be in MOA. This is because when compensating for wind we are thinking in terms of MOA or minutes of angle.

    My quick course on minutes of angle (MOA) is that if a bullet is off from your aim point at 100 yards, it continues to travel down range at that same angle. For example, if a bullet is off left or right 1” at 100 yards it will be off 2” at 200yds, 4” at 400yds, 9” at 900yds and so on. Once a rifle is sighted in dead-on at a desired distance, the largest factor that causes a variation from center of target is the wind. Printing out a range card based on your rifles ballistics
    before practicing is a great idea. This will allow you to know how much wind deflection there is down range at different distances.

    With the Huskemaw Optics scope and turret system, we print the wind hold value above the appropriate yardage number. These MOA values are based on 10MPH wind. In this way as we dial to the distance of our desired target, we can see the wind MOA value number above the yardage number. We hold the correct MOA value by moving the center crosshair into the wind and hold the correct MOA hash mark where we want the bullet to impact the target.
    (US Patent 8,365,455 B2)

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    Now that we have a basic understanding of how much wind we need to hold at a given distance, let’s work through some scenarios for better clarification. Let’s say we are right at 500 yards lined up on a big bull elk. The first thing we do is to point our wind meter at the elk, this is to make sure we are acquiring the wind speed in the flight path of the bullet. This is the value we are most concerned with. Let’s say we have a left to right wind blowing at 8mph and we to dial the turret to 500 yards, our turret says we need to hold 2 MOA for a 10mph wind.

    Next we look at the vegetation at our position. We look down range and evaluate what the vegetation looks like compared to our position. We do this at 1/3 to 1/2 way to the elk. We see there is some tree limbs right behind the elk, not that it matters as much, but because it gives us a better understanding what the wind is doing in general. We check the wind meter again, and it says 10.5mph, still well within our 2 MOA value.

    My desired aim point is mid-way up on the front shoulder. This is because I want to anchor the bull right where he stands. I push the center crosshair into the wind and hold the second hash mark where we want the bullet to land. I remain conscientious of the wind on my face and the vegetation down range. When I am confident that the wind has not changed, I concentrate on my wobble zone as I slowly break the shot.

    This broadside example is ideal for long range shots, especially in windy situations. If an animal has its head up like the elk in the picture to left, look at how much room there is for error in the event the wind picks up or lets off. 3 MOA in either direction, and this shot is still in a vital zone. If you held low in the front shoulder you would lose the amount of vital area in both directions from the aim point.

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    Next let’s work through a different scenario to get another look at how to read the wind.

    It’s late afternoon on the last day of your bighorn sheep hunt. You’ve put in for over 20 years to get this once in a life time tag. You’ve passed on three decent rams but they just weren’t quite what you wanted to settle for. You have a big ram spotted on a hillside across the canyon. You have him ranged at 725 yards and he’s looking straight at you. If you move any closer, there is a very high probability he will spook and disappear over the edge. As you look through your HO scope, you dial your side parallax so that as you start to lose focus of the ram, you start to focus on the mirage in between yourself and the ram. The mirage is blowing left to right at a 2-3 o’clock angle. This tells you the wind is blowing right at 10mph down range.

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    As you dial the turret to 725yds, it tells you to hold 3.5MOA of wind. You instantly know your 4MOA hash mark (Seen in Red) is the biggest one, so you split the point of his shoulder with the 3 and 4MOA hash marks knowing that the bullet will impact between the two of them. At this angle you’re confident not only with a one shot kill but you should be able to drop him where he stands.

    This is the reality of many of the situations hunters are faced with each year. Having the ability to range a target with a rangefinder is a great advancement in the hunting world. This instrument has given us the opportunity and capability for advanced bullet drop compensation. Wind meters, on the other hand, only give us the ability to know what the wind is doing at our direct location.

    We must develop other methods for determining what the wind is doing down range as the bullet travels to our intended target. In addition to reading vegetation and other organic elements affected by the wind, mirage is the most commonly used indicator by experienced shooters. Although it’s not important for shooters to know all the science of what mirage is, let’s have Wikipedia explain the causes.

    “Cold air is denser than warm air and, therefore, has a greater refractive index. As light travels at a shallow angle along a boundary between air layers of different temperature, the light rays bend towards the colder air. If the air near the ground is warmer than that higher up, the light ray bends upward, effectively being totally reflected just above the ground”.

    All of us have been driving down the highway on a hot summer day and witnessed what appears to be water ¼ mile or so ahead on the blacktop. If you actually studied it you may have noticed what appears to be waves of evaporation coming off from this imaginary pool of moving water. If the wind is blowing you may have also noticed that the “evaporation waves” are moving sideways with the wind. This is what we are looking for when reading mirage in windy situations.

    The best way to do this is by using a very high quality spotting scope or a rifle scope with a parallax adjustment dial. The objective is to dial the optic “out” of the focus of our target. As we lose focus with our target, we can begin to focus on the mirage that starts to appear in between our position and the target. This allows us to see how the wind is affecting the mirage down range. From this we can get a good idea of what the wind speed is doing down range and in the flight path of our bullet.

    There are some fundamental things we need to know before we can start to determine the cross component value of the wind. It is not simply how fast the wind is blowing that matters, it’s at what angle it blows across the flight path as our bullet travels down range towards its target. First, we need to understand that a full value wind is when the wind is blowing directly perpendicular across the target path. (See Rosette in diagram)

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    The 1, 5, 7, and 11 o’clock wind directions are called a ½ value wind. The 2, 4, 8 and 10 o’clock wind directions are approximately 85% of full value. The general rule is that if the mirage waves are boiling straight upwards there is either a head wind or a tail wind that cancels out any side deflection of the bullet. In this case, you do not hold a wind value.

    By reading mirage waves moving the same direction that the wind is blowing, we can see that if the mirage is moving at a 1-2 o’clock position, it is a 5mph wind. If the mirage is blowing from a 2-3 o’clock position, it is a 10mph wind. If it is streaming across at a 3 o’clock position, it is 15mph, and if it is streaming horizontally and starts to wave it is a 20mph wind or faster.

    Having a wind meter is a big help in these situations. Reading the wind at your position, looking at the vegetation at your position and down range in conjunction with mirage can lead to a very close determination of the actual wind speed.

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    Because our HO turret MOA values are based on a 10mph wind value, we can easily use the MPH values from the mirage to know how many MOA’s to hold at a given distance. Is it a 5, 10, 15 or 20mph cross wind? We can then determine the correct MOA hold values by reading the 10mph values printed on the turret, cut the value in half for a 5mph wind, 1-1/2 x it for a 15mph wind, and 2 x it for a 20mph wind.

    For instance, if you dialed your turret to 700 yards and the MOA value above the 7 is a 4, this means that at 700 yards you need to hold 4 hash marks over. You do this by pushing your center crosshairs into the wind and hold the 4th hash mark on the downwind side. If the wind is blowing 5mph you hold only 2 hash marks, 15mph you hold 6 hash marks, and with a 20mph wind you hold 8 hash marks.

    To some this may sound complicated, while others may think I am making it sound easy. I assure you that reading the wind is like anything else you have done. As you start practicing with your wind meter, reading vegetation and mirage, you will surprise yourself. You will learn that in most wind conditions you can become very proficient. However, you will also learn that in gusty winds that are constantly changing, it can be very difficult. The most important thing to know is that with practice you will know what you can and cannot do when faced with windy conditions in a real-world hunting situation.

    I believe that as we practice and develop better skills and proficiency, we are much more likely to take ethical shots in the field. I want to encourage you to consider taking a long-range shooting course. We have never witnessed anyone that did not express their new-found confidence in their ability to shoot longer ranges after attending one of these schools. Always remember to never take a shot at an animal if you have not practiced similar shots in the same field like conditions at the range.

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