Effects of Mirage - Need input.ADDED TARGETS

Kelly Timoffee

Kelly Timoffee

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Need some advice from the experienced crowd on the real effects of mirage.

Today's outing was about 17-19C in a gravel pit which I frequent for my shooting. Was over cast but with a strong steady wind and gusting quite high at times, my estimate would be as high as 10 MPH maybe more.

I did my zero at 200 yards, that was fine.Moved out to 300, made my correction, shot a bit, was able to manage 5. to .7 MOA groups.

Then moved out to 400. Then the clouds moved off and there was the mirage just like that. I was able to get my correction for 400 yards but the groups were 1 MOA to 1.5 MOA.

My correction for the wind was repeatable but the groups were awful.

Is this what I should expect or maybe it is the shooter???
 
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all sorts of factors come into play as you move farther out. Mirage is just a displaced image at distances by light rays. More of a viewer thing. Your groups could have opened up because you were thinking you were aiming at the target but it was distorted so your point of aim was off. That's all really it would do. Mirage is a great way to read wind by the way the light waves are moving. More likely that the wind was playing around with the bullet. Little errors on the shooters behalf start to become noticed at long range. If you said there was a 10 mph wind at the target, well what was in between the muzzle and the target also effects it. I've seen 10 mph winds hook 168 grain bullets hard left and right before impact at 800 yards.Bullets can even get pushed around at 200 yards with adequate wind.
 
Yes this is pretty much what you should expect until you become a better wind reader.
If the groups are verticle its probably you, ammo, or whatever.If they are horizontal its tour wind reading.
If its a combo then its probably both!Practice! ;)
 
I had the same experience a few weeks back shooting at 300m. Normally I shoot in the evenings but that one time it was midday and sunny which produced a terrible mirage in the gravel pit. My groups openned up 1/2 to 1 MOA which I can only attribute to the mirage as the wind was what I usually shoot in. Just to give you an idea of how bad it was, normally I can easily see my shots on target but on that day I could not see the shots and when the mirage was at its worst, the thick black target circles would nearly disappear.

While I'm sure there are tricks/tips to help read through the mirage or even use it to determine wind values I think gravel pits really lend themselves to having extreme mirage. I know the mirage was nowhere near as that bad when I shooting gophers in the farm fields on hot and sunny days.

Steve
 
If you want an interesting exercise, try this. Mount a rifle scope on a tripod, or use your spotting scope if it has a reticle. Early in the morning before mirage appears set up the tripod mounted scope to center on your target, and don't touch it again. From time to time throughout the day check the position of the reticle relative to the target.
 
I wish someone would post a You tube video detailing mirage, its negative effects and how to use it to read wind etc. Not sure it would be easy to do but would love to see one posted by an experienced shooter.
 
Mirage is just wind that you can see. Wind flags lie but mirage tends to be a truer indication of what is happening down range. Even on days that the mirage does not seem to be running, if you focus your scope about 1/3 of the distance to target you will see what the real story is with the mirage.
 
warrenb that could be done but I am not aware of any such video. Problem is, one could only make such a video while shooting on the range, and that sort of time is pretty rare. Of course if somewhere the right combination of video geek and shooting coach were to get together, they could make some really wonderful and useful videos.

This is the sort of thing though that you will see in person by going to a rifle match, in particular if you participate in a coached match as a scorekeeper or a plotter. Also there is a "Circle Training" system that has been developed over the past few years that is a really fantastic way to see learn and discuss this sort of thing.

The sole quibble I have with Maynard's post above is that sometimes mirage also lies (I am remembering a particular magpie at 600 yards in 2000... that shot still puzzles me). But the important thing is that mirage is by and large your friend when it comes to shooting; given a choice I would nearly always choose to shoot with mirage rather than without mirage.

There is another kind of mirage you can also get, "barrel mirage", which is caused by heated air rising from your barrel. If there is even a whisper of wind it'll be blown away and not be a problem, but if you are shooting under near-dead-calm conditions (oftentimes you'll get this when you are testing ammo in the evening) you can get pretty bad barrel mirage. In my experience barrel mirage will really wreck your sight picture and will also shift the apparent position of your aiming mark (and therefore really ruin your testing). I will do anything I can to deal with barrel mirage (mirage band on barrel, or scope tube, or use a fan to blow air across the barrel).

With respect to regular (not barrel) mirage, in my experience I have never been able to observe a shift in the aiming mark due to mirage, but as a fair warning to this comment I will say that a number of very experienced shooters think that this is true, shoot accordingly, and oftentimes shoot higher scores than I do... so they might be correct!

Boomer I have never had the opportunity to do the test you describe, which of course is the right test to do. At some point would you be willing to say what you have observed, i.e. shift or no shift?

EDIT to add: the reason behind Maynard's "focus your scope 1/3 of the way in front of you" is so that you see the mirage that is produced by the "near wind", that is to say the wind that is closer to you rather than the target. The reason this is useful is that the "near wind" has more of an effect on your bullet than the "far wind"; if they differ, you need to weight the "near wind" more heavily than the "far wind". When you focus your scope like this the target will be slightly out of focus but that is not a problem you can still see the lines and the spotting discs and know where your shots are landing.
 
Here are my targets which give the best example of my results.

The 300 yard target I am content with, a little more practice, maybe slight load tweaking.

The 400 yard target , not so happy with.

I am confident in my form , trigger pull, etc..........

Hopefully this will let the guru's better guide me on this issue.

0018.jpg


0019.jpg
 
It was probably the heat waves.I was out shooting in 28 degree weather the other day, when I went above 14 zoom the heat waves played havoc with my view.
 
I am shooting a 700 with Kreiger barrel 26", 1 in 9" 7mm-08.Action has been trued.

The Scope is a Conquest 4.5-14X50

The load is 168VLD, 42.5 grains of H4350 , CCI BR2 , and Lapua brass.Approx 2620 Ft/sec @ muzzle.

400 yard target is 6.8" across the rings, the red ring is 2.25"
 
Well, I went out today , WAY hotter 27C or so.

Wind was light, didn't have any improvement, maybe even worse at 400 yards. Did however have better horizontal spread due to less wind to deal with.
 
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A few comments:

- Your 300 yard group has four shots in it, your 400 yard group has six shots in it. If you were to have fired two more shots at your 300y group, it would be impossible to make it smaller and likely that it would have gotten a bit bigger. How much bigger would vary from group to group but on average perhaps 30% bigger; so your ~0.5 MOA group might be expected to be .65MOA if it were a six-shot group.

- by eyeball I think your 400 yard group is about 4 inches high by about 5.6" wide (about 1,0 MOA high by 1.4 MOA wide). Especially on a variably-windy day as you describe it is much more meaningful to use a group's height as an indicator of the rifle+ammo+scope+shooter precision; the width of the group is influenced by how good you are as a wind-reader and while this is relevant to how you might place in a match it is not relevant to the question of how precisely you plus your rifle ammo and scope are delivering shots.

So in my opinion what we have here is that you got about 1 MOA at 400y versus about 2/3 MOA (had you fired six shots) at 300 yards.
 
Great thread Kelly. Some good gems to consider here.

I seem to keep coming back to the details outside of the mirage topic, just because it is easier to nail down for me. I am not trying to hijack the mirage topic. Wind or mirage kicks my a** most of the time. More practice, more practice, more.....

So here is my two bits to eliminate one variable.
I view the vertical in the strings in your targets and wonder what your best condition groups are like at 200m. The elimination of easier variables is a valuable step, regardless of the end purpose of your rig.

For the detailed folks, a 1/4 to 1/2 minute gun is competitive with the least vertical tune possible, shot and confirmed at 300, 500, 600 or more yards. I am sure you understand what you are looking for is the least vertical possible at the accurate distance you can shoot. The more vertical in your baseline the worse your groups will get at distance. Not saying this is the issue you are encountering, just saying what we strive for in our load development when being picky.

For instance, I have obtained flat line groups with tuned loads to a specific condition at 200m with a F class/hunter rig. Then when items such as large temp change it may be possible for vertical to creep in and blow my tune to hell. Loads developed outside of a temp range (say +/- 10 degrees as a start with hodgdon powder, possibly less with others) will act differently than those of your base line. This will send you out of your barrel node particularily where and that node is short.

If you have confirmed your best load for the "range of conditions" then by all means disregard. My two bits....

Elky..
 
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Shot 6, no green marker, was not of the group.

I basically just wanted to get my 300 yard zero then move out to 400 for practice.Needless to say I cut it short that day.

Here is one for thought, as the barrel heats between shots is there a POI change as the mariage from the barrel get's worse? I know it is easy to eliminate, I'm just curious.

rnbra-shooter said:
A few comments:

- Your 300 yard group has four shots in it, your 400 yard group has six shots in it. If you were to have fired two more shots at your 300y group, it would be impossible to make it smaller and likely that it would have gotten a bit bigger. How much bigger would vary from group to group but on average perhaps 30% bigger; so your ~0.5 MOA group might be expected to be .65MOA if it were a six-shot group.

- by eyeball I think your 400 yard group is about 4 inches high by about 5.6" wide (about 1,0 MOA high by 1.4 MOA wide). Especially on a variably-windy day as you describe it is much more meaningful to use a group's height as an indicator of the rifle+ammo+scope+shooter precision; the width of the group is influenced by how good you are as a wind-reader and while this is relevant to how you might place in a match it is not relevant to the question of how precisely you plus your rifle ammo and scope are delivering shots.

So in my opinion what we have here is that you got about 1 MOA at 400y versus about 2/3 MOA (had you fired six shots) at 300 yards.
Click to expand...
 
Here is my theory and key points I have picked up around mirage:

Any distortions are bad carma. I think this is the key component, it only really helps when you know the position of the last shot and the mirage and wind condition it was shot under.
Avoid a shot when the mirage is on a boil. Even more an issue when shooting prone on a hot, light wind day.
Best when a steady mirage, ripply and rather straight in nature. (incates a steady wind)
Less best when the mirage is rolling. (indicates an inconsistent or lighter wind)
At each shot determine mirage and wind direction. A change can happen quickly and even from a completely different direction.
Wait for your condition to make another shot. Again, better determined when you know the position of the last shot and the conditions it was shot under.

Leave your adustment knobs alone.......repeat. Consider, Adjust, W.A.G., and shoot....
 
I much prefer shooting with some mirage than in a no-mirage condition. We are concerned about strength of wind and the angle of the wind. Mirage looks like waves. Large waves means a gentle mirage. Small waves means the wind effect has got stronger. Either it’s more wind or changed closer to 90 degrees. So the mirage automatically factors both strength and angle. It will pick up subtle changes that cannot be seen in flags.

Also, the wind close to the ground is of more interest to me than the wind 30 feet above ground where the flag is.

Shooting in a gentle snow storm shows similar changes.

There is a tendency for shooters to ascribe effects to factors they know about. But the results can be influenced more profoundly by other factors. In this case, I think your groups suffer by a vague target that gets even worse as the mirage makes it fuzzy.

I cut black paper into squares and use a glue stick to stick them on the back of a large handgun target. The crosshairs are easy to aim at the corner of the square. I use an inch of black per hundred yards. A 4” black square shows up well at 400 yards.

4TARGET.jpg


The other variable is parallax. Do you set the parallax to 400 when you move back to 400? Or do you set it and then sandbag the rifle and wiggle your head side to side, looking for the crosshair movement on the target. You have to dial the movement out. I only have one scope where this happens to be the distance on the ring.
 
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