To preface this, I have little or no scientific knowledge to back this up, it's just something my mind tells me should be true: My theory is that, no matter how bad the mirage is, it will not move the target any more than its own size. Example: No wind so mirage is going straight up...the target you'see' will be no more than the original target directly above itself...no space in between, or, with severe mirage going up and to the right, the target you see will be no more than the bottom left corner of that target touching the top right corner of the real target.
(Do I have you confused?) Teach me...

P_102

I'll bet JG can elucidate on this subject. That's right up his alley.

You're right about size. It's never come up in my thinking. Mirage will distort the target, making it difficult to find the edges. Fortunately I get to spent many hours a year behind glass, and most of the time there is mirage. Target color and background color have lots to do with what you can or cannot see.

You are well aware of white targets on my range. As well as a black dirt back drop, a shade backdrop, or green grass and trees as a backdrop. It is the easiest to see white with those backdrops, in my opinion. However, I have set steel in Terrel county. The whole place is limestone. I knew white was going to be a terrible color because of the color of the backdrop. Krylon makes a neon pink, and it was perfect.

When mirage is awful, like this time of year, it is difficult to find the edges of the target, making one think the target is actually smaller than it really is.

I will add. What my mind does, is decide where the average of the target is. When it looks like it's dancing, find the portion of the center that seems to stay put. Make your wind hold based on that portion, of the diameter of center. Obviously, backing down magnification is almost always a necessity, depending in distance, thus the First Focal Plane usage.

At least thats how I get it done, in heavy mirage.

At 1000ish I've seen a mirage boil move poi over 10inches.

Your corrections were wrong.

Well it's not moving the impacts but the perceived poi vs poa. Most associations are that the image floats or distorts up causing impacts to be high. Square range guys tend to have a better theory or compensation of it but there is no cut or dry solutions.

You could probably call mine a square range. In my minds eye, I go back to target color, against background color. I can visualize my far ones, and 800 is the worst one to look through the mirage, most of the day. Zero line is shade, an entire field of sun, target is in shade, until late in the day. You've really got to study it for several seconds to figure out where it "really is". It is one of the most difficult topics to explain in distance shooting. You know that.

JG finally makes sense

Chris, the timing for this post could not have been better. Great info guys and I appreciate it very much.

What happens when you're on a "range" you've never been to before?
Like, hunting sheep (white target w/white background) in the mountains w/heavy mirage? How would you cope w/that?

Weather conditions during a sheep hunt are not likely to be above 85° with a 90% humidity.

Turn down your focus to get a read on the mirage. In other words if the labeling, on your side focus is correct, and everything is clear at 500 yards, and your focus knob is sitting on the 500 yard setting, turn it down like a closer shot to 200 yards, or less. The target will be blurry, but the mirage will be more prevalent to get a read. Make a decision, refocus on the target, shoot.

When target color, and background color are blending, your going to have to hope you bought the best glass you can afford. That's where clarity, and definition come into play.

And again, if mirage is very thick, you have to turn down magnification.

Generally speaking...^^^^ this is the answer.

Really really good glass helps too.

A few others comments, not mentioned thus far -

Try not to shoot into a "boil." That is the absence of any air movement that causes the mirage to look like swirls in boiling water going upward.

Wait a moment and usually a bit of breeze, even very faint, will cause the mirage to bend right or left.

Even a slight bend to mirage will improve the image and shot consistency on the target.

For target shooting, just wait for a consistent pattern, i.e. all shots with the mirage bending the same direction and amount for each shot.

But, really try to avoid the "boil," it makes things much less consistent.

Also, raising the rifle even a couple of feet above the ground can reduce the effect of mirage.

A sitting or kneeling position, even though less steady, (reminder to bring some shooting sticks while out hunting) might produce a better result in some extreme conditions due to reduction of the mirage.

As FJG alludes to above, focusing closer than the target can also be used as a tool to check for wind patterns that might not be obvious.

The "hidden" air flow can be a real factor where there are slopes, draws, or changes in the surface such as water, snow, or changes in surface cover.

Cold air also can cause some really bad mirage, especially early in the morning when the sun first starts to hit the surface.

Practicing shooting in a heavy mirage is a useful exercise for both hunting and target shooting.

Tomorrow the boil will be unavoidable, as the clock is ticking.

Last weekend the boil was unavoidable, the clock was ticking.

I would rather try and help people learn how to deal with it, than wait on it.

Coyotes and hogs still show up in summer. Learn to shoot in the mirage you have, and kill the bastards.