The Straight Scoop on Mirage - Originally written Jan 2010

The first time I ever heard about mirage I was watching some old movie when I was a youngster and the hero of the movie was wandering aimlessly through the desert, and he saw a city shimmering on the desert sands ahead of him. As he ran towards that city with the last of his remaining energy, he sadly discovered it was only an illusion of a distant city that had been projected towards him by the refracted light that had been bent by the heat waves rising from the desert floor. It was a mirage.

    At least that is how my dad explained it to me at the time. But that was well over forty years ago. If I'd had any idea how much mirage would mean to me in the rest of my life I might have asked for a better explanation. Actually for most of my life I never gave it a thought unless I saw the heat waves rising from the road in the summer time as I drove down the highway and could see the sky where the road was supposed to be and thought back to that city that seemed to be where it really wasn't.

    Fast forward a number of years and there came a time in my life where I decided it was time to try my hand at long range shooting. You know... back when I thought 300 yards was long range. I began the trek up the steep learning curve of knowledge in the quest for truth as to how to hit the target so far away.

    Like most in that stage of ignorance I read everything I could get my hands on, and listened to everything that was said at the range, and assumed that everything I read or heard was gospel. After all, they shot better than I did so they must know what they are talking about... right?

    Well eventually I learned that not everything that is written, nor everything that is proclaimed at the rifle range by the local expert is accurate. It simply could not all be right when sometimes they totally disagree. I eventually began to realize that some people like to write and others like to be the local expert, but that doesn't make either one of them right..... Just opinionated.

    Now don't get me wrong. There's nothing wrong with having an opinion. I've been known to have a strong one or two myself, and I always respect those who do have. I just hate it when they want to share their opinions and they start with a statement that begins with "I heard", 'I think', "I feel", or worse yet "Lee Shaver says". I prefer opinions that begin with first hand experience and knowledge gained by it. I've come to feel this way after being lead astray by opinions I have listened to in my younger years that were not necessarily based in fact.

    A real problem arises when you hear two opposing opinions about a matter from two experts that have proven their point to be true to the best of their ability. This is the kind of problem that you have when you start talking about mirage and how it affects shooting conditions.

    The first book I read on accurate shooting had a whole chapter on Mirage. It went into great detail to explain how light was bent as it traveled from the target to our eye, passing through the heat waves that can be seen in the air, which are caused by heated air that was rising from the warm area near the ground and passing through cooler air above the ground. The explanation went on to explain how the light is bent to make the target appear to be somewhere it wasn't just as a fish will appear to be in a slightly different spot than it really is when you look at it in a pond or fish bowl. The light is bent or refracted at the point the air and water meet because light travels through that barrier, and is turned just a little. The same thing happens ( the book said ) when you have warmed air from the ground rising through cooler air above. The point at which these two different temperature air flows meet causes the light to bend just a little as it passes through this border area because of the differing mass of the two air flows. I'm sure there are any number of guys out there that could explain it better than that, but you get the idea anyway.

    The book went on to explain that this mirage effect would actually make the target appear to be somewhere it wasn't, and if it did so and we aimed at the target we could see, we might well miss the target because the image we saw was not where the target really was. The target generally appears to move in the direction the wind is blowing ( the book said ), so you should figure on aiming upwind of the target you see to hit the real one.

    I've seen and heard this same basic explanation many times over the years since I first read it in that book, but I was always confused. If I was already aiming into the wind because the wind blows the bullet, should I allow a little more for the mirage effect and if so how do I know how much.

    Apparently I am not the only one that has been confused by this. I hate to think how many times I have heard a shooter expounding on how he adjusted for the wind and then adjusted for the mirage also.    All the while it seemed to make sense, but I just kept thinking that if it were true then you should be able to detect it in a scope as you looked at the target. Wouldn't the target be moving around in the spotting scope while you looked at it if the wind changed directions?

    Then I read an account by a bench rest shooter about how he would watch carefully as his target would be stretched out by the mirage to the right as the wind picked up from the left, and then the rest of the target would snap to the right to make a clear target at one specific wind speed, and he would fire his shot at that time. When the wind slacked off it would then move back to it's original position to the left a fraction of an inch, and be equally as clear, just in a different spot. So I assumed this expert certainly knew what he was doing and won the match so maybe it was true that the target moves with the mirage. I never saw anything like that happen through my spotting scope at the silhouette range so I never had an idea how to adjust for it. Still confused I guess.

    All the while there are very experienced shooters who say the mirage effect never moves the target, but in fact the heat waves that we call mirage are moved by the wind and are the best wind speed indicators there is. Nothing more and nothing less. The strongest proponents of this theory are the long range shooters and high power rifle competitors. The first time I heard this theory I thought that it made a lot of sense too, as that reflected more of what I saw when I looked through my spotting scope, but how do you explain the expert riflemen that write about what they see through the scope of their bench rest rifles.

    There have been numerous tests performed over the years to prove or disprove both theories about what the heat waves do to what we see.

    In about 1903 Dr. F. W. Mann, a well known rifleman and constant experimenter of his time performed a pretty lengthy and severe test by building a series of "V" rests to hold a scope, and made them so they could be driven into the ground in various places, placed at various angles and etc. One of the rests was even placed so that the line of sight of the scope when placed in the rest, was over open sand and went within inches of the top of a sand dune at one point where the heat waves rising from the sun warmed sand would be the greatest.

    He then placed small targets at various distances from the scope rests in such a way that when he placed the scope in the rests the cross hairs of the scope would be centered on the target. He then made his circuit several times a day for several days to place the scope in each rest and make note of where the cross hairs were on the target each time.

    In his book he went into some detail describeing how he had performed the test, and then if I remember correctly he just summed it up by saying that there was not one time when the cross hairs where not on the small target each one was aimed at, no matter the wind direction, light conditions, nor time of day.

    Well that seemed pretty convincing, but Dr. Mann was an experimenter that had a goal of dispelling old wives tails as he called them, and learning the truth of what really caused bullets to land where you did not expect them. In this particular instance it was obvious that his testing supported the belief he held prior to the test, so it received a less than scientific reporting, and no further study from that point on. The problem was solved in his mind, or should I say that he proved his opinions to be correct.

    Not too many years ago I read where a shooter had set a tripod up with a spotting scope on it aimed at a 500 meter ram and left it untouched the rest of the day and checked it periodically to see what if anything was happening. I don't remember it in great detail, but suffice it to say that it was reported in print that the center of the field of view of the scope traveled across the ram in an arc as the day wore on. What was not reported was if the ram moved when the wind changed direction as it should according to the visual movement theory, or if something else was going on.

    The real flaw I saw in this test was that the scope and tripod were left out in the sun all day, and the leg of the tripod with the most direct sunlight on it would have most likely warmed and expanded to cause the target to appear to move in the scope, and as the day wore on and the sun moved across the sky it would have warmed the other legs at various times causing the documented movement. If one leg of the tripod were to warm up to say 20 degrees F warmer than the other legs, that leg would grow something like 1/32 of an inch in length more than the others. In other words it was entirely possible that the scope was moving and not the target.

    So over a hundred years after Dr Mann wrote his book the argument rages on as to whether the heat waves move the apparent location of the target or if the heat waves are just moved by the wind and should be used as wind indicators. Within the last year I have read two or three articles in magazines on mirage and wind reading, and a couple of book references on the subject, they each held up the theory they believed in, without any real consideration for the other theory and the expert shooters that live and win by it.

    After fifteen years of studying and using mirage as a shooter I have come to learn that the answer to this problem is simple really, as most are once you understand them completely. Both theories are correct, and yet both are incorrect, or perhaps more properly stated, they are sometimes incorrectly applied.

    In reality it depends on the relationship of the target size to the size of the heat waves. A general rule of thumb I have been using for years is that the target will move no more in the mirage than the size of the heat waves. It’s not precise, but then, rules of thumb are not intended to be.

    A bench rest shooter that is shooting at a target of perhaps a couple of inches in diameter at 200 yards will indeed see his target move around in the mirage when the heat waves are perhaps four or five inches wide, but a six foot square target at 1000 yards will not appear to move when the heat waves are the same size, especially when viewed through peep sights
  
    A perfect example is a typical day of 1000 yard practice for Mon Yee and I, west of Dodge City where we often  practice in the summer months. The winds and mirage of western Kansas can be brutal, and are a perfect training ground. You loose your fear of the wind and mirage real quickly once you get used to your ammo box blowing away when it is still half full, or mirage so bad that you don't need your spotting scope to read it 500 yards away.

    A typical day of practice would begin early with light to moderate winds, perfect early morning light, and no mirage. The target would be a six foot square steel target painted white, setting on the ground, with a 44 inch round dinger plate mounted in the center painted black for an aiming point, and in the perfect center we always put a small two inch diameter white dot so we can have a center to work towards. In the center of the white dot is a 5/8 inch diameter nut that holds the 44 inch plate to the target. We always start with something of a bet, such as the last one to hit the nut buys dinner that evening.

    We share the target and fire in rotation. We can easily see the bullet splashes on the target with our spotting scopes as they get closer and closer to the little white dot in the center of the target. Each time we fire we have a contest to see who's shot is closest to center. If we are lucky we get a complete score fired or maybe more before the sun gets up far enough to warm the ground a little and we start seeing the first of the heat waves that will be with us the rest of the day.

    At the first hint of heat waves we see the little white dot in the center of the aiming black start to wiggle, but the target looks perfect other than a little fuzziness on the outer edge of the black, and we can still see our bullet splashes, but they too are starting to wiggle a bit. As the heat waves grow heavier the white dot will begin to dance around on the center of the target within an area of about four to six inches in diameter, the 44 inch black is just wavy around the outside edge, but the whole disc does not appear to move. At this point it becomes difficult if not impossible to see the bullet splashes on the target as they are lost in the mirage, but when the wind blows a little extra hard it will blow the mirage out and we can see the hits regularly. We can still aim at the 44 inch circle with our peep sights without any problems though, the sight picture looks fine because the fuzziness of the edge of the black circle is smaller than our ability to see.

    As the heat of the day sets in upon us, the white dot in the center of the target will jump around violently in an area up to ten or even twelve inches in diameter, but still mostly within six to eight inches. The 44 inch circle starts becoming a misshapen wavy blob that is constantly changing shape, but not necessarily location. It starts looking fuzzy and poorly defined through the peep sights, and it becomes impossible to locate the hits on the target so we switch to a paper target on a pull type frame with pits and we take turn shooting scores and pulling targets the rest of the day.

    The paper target sets about eight feet higher in the air so we get a short reprieve from the worst of the mirage that is close to the ground but it will be short lived. During the hottest part of the afternoon we will see mirage waves coming across the field of view in our spotting scopes that may be ten feet high, and as they pass the target the whole six foot square target may move a foot or more higher and then drop back down to it's original place. The five inch diameter shot markers will be wavy blobs of color on the target, and the 44 inch diameter aiming black looks poorly defined in the front sight and may look like it is swimming around a little. This too will pass though, as the afternoon wears into evening and we can once again go back to shooting the steel target, and as we shoot we can watch the little two inch white dot in the center of the target slowly cease it's dance and settle back into a stationary dot.

    This example perfectly highlights the fact that small targets will move around in the mirage when the large ones may not. If we were shooting at a two inch dot at that distance we would have sworn the target moved around the whole time there were heat waves to be seen, but our larger target moved only under the worst of conditions. Not once did we ever have to make a sight adjustment that was not predicted by the wind in the flags, and verified by reading the way the wind moved the heat waves.

    So the next time you read an article or book reference that assumes the target may not be where it appears to be, please make sure they are talking about little targets that may get lost in the heat waves. If they are talking about the mysterious ability of a large target to appear to be where it is not, then please just roll your eyes and go find something instructive to read. And that, as Elmer Keith used to say “is the truth as I see it”

Installation Instructions for Lee Shaver Supergrade Soule Sights

The Supergrade soule sight should come with the detent spring and one of the screws in place in the base with tape holding it in place. This is simply done so you will know which end of the base the spring goes on, which screw is to be used with that spring, and approximately how it all goes together.

You should first place the sight on your rifle, and install both mounting screws and the spring, and just snug them up a little.

Next it is important to level or at least check the level of the sight in relationship to the rifle, and make sure it is not leaning left or right when viewed from the rear. If the sight is tipped left or right due to machining tolerances of the sight or tang of the rifle it will cause you to use up some of your windage adjustment to get the sight zeroed, and will mean that you need to make a windage adjustment every time you adjust to a different elevation.

To check the sight for this possible tipping. You simply put the rifle in a padded vise or cleaning cradle, and using a small level, you level up the action of the rifle as true as you can, and then check the level of the sight. If it is not matching the action of the rifle then you need to take the sight loose and place thin shims un the side of the base it is tipping towards, and tighten the screws and check again till the sight stands level with the rifle.

The shims can be paper or steel. I use business card type paper cut to size and blackened with a magic marker.

Once you have the sight leveled left and right then you can set the angle for and aft. If you still have the screws just snug it is quite easy.

The detent spring has a slotted hole where the mounting screw goes through it. This slotted hole is used to adjust the angle at which the sight stands when it is clicked into the detent position.

I simply stand the staff up into the detent and then use a small punch and very small hammer to peck the spring for or aft till the staff stands at the location I want.

I usually set the staff straight up or perpendicular to the bore line for short and medium range shooting, and I set it leaning forward about three degrees for 1,000 yard shooting.

Hope this helps,

Lee Shaver