Advanced Marksmanship Correcting for mirage

[Bantam1]

I did a search and read what I could find on mirage, but I did not see anything specific about how to correct for it. I typically do not shoot in hot places during the summer months. Last weekend I had a friend in from out of town and he wanted to shoot long range. He can shoot and stacked them at 1000 yards. So I moved him to 1400 for more challenge with the wind. Normally I can get several rounds downrange before the mirage get's bad from the heat off the barrel. This weekend in the desert spot I shoot at it was 90-103F. No shade so the barrel was hot just from ambient temps and the sun shining on it. Normally I shoot out there in the fall-spring until it's too hot.

I let him do all the shooting with my 6.5 CM using factory Hornady 140 ELD-M and I stayed on the glass to give him wind calls and corrections. I noticed he would be good making hits and then after 2-3 shots it was like he was walking all over the place. I confirmed the dope, double checked the wind and everything was correct. Previous impacts were essentially dead center. I stuck the fan in the barrel and cooled it down. I laid some wet rags over the barrel to help cool the surface also. First round impact, second impact then 1.5-2 mils high, 1.5-2.5 mils wind (was getting harder to read the wind in the mirage in my Luepold spotter). My rifle has a 26"Bartlein M40 profiled barrel. It doesn't get super hot usually.

I made a turret correction, checked the weather DA changed by 400' which shouldn't affect that much. It asked for .3 mils less elevation. Let the barrel cool and it would be back on center or close if he made a good shot or my wind call was right. Once he made 3 shots, now it was low. Adjusted elevation back to where it was and elevation was high, or really close with a wind call miss. Light winds 3-6mph from 1:00-3:00 (switching). The only thing I can think of is the mirage was altering where he thought he was aiming. Can mirage affect vertical and horizontal picture?

 

[Diver160651]

It bounces the image in the direction of the wind or rising air “if you’re talking shimmer”. That’s the dancy little waves you see in your glass most often.

Mirage Is actually different most people see when shooting, depending on the relationship between the ground/water and air the image can be displaced low or high

 

[Bantam1]

I assume it's not a fixed amount to adjust for based on the effects.

The waves I noticed through the spotter were going to 10:00-10:30 most of the time. So I should assume I need to add elevation and reduce the wind call if the wind is coming from 1:00-3:00? Just trying to understand the effects a little more to compensate in the future. I know shooting in it is the best method to learn, but if I can draw from the knowledge of some of you it might shorten my learning curve a little.

 

[Diver160651]

I assume it's not a fixed amount to adjust for based on the effects.

The waves I noticed through the spotter were going to 10:00-10:30 most of the time. So I should assume I need to add elevation and reduce the wind call if the wind is coming from 1:00-3:00? Just trying to understand the effects a little more to compensate in the future. I know shooting in it is the best method to learn, but if I can draw from the knowledge of some of you it might shorten my learning curve a little.

????

Generally talking one wind zone, The shimmer is travel in the direction of the wind, not opposing in anyway. Targets that are not completely blown out, tend to bounce back to their home position. That gives an indication on your aiming point, the rest helps you make your wind call.

The hardest to determine wind speed for me is 11-1 and 7-5 in long range low wind. These look like wind running L-R or R-L, flatter in appearance than a boil so they can appear like faster winds.

 

[Bantam1]

I realize that, but that is what I was seeing through the glass and checked the wind with my Kestrel and confirmed direction with a flag. I know it sounds messed up, but that is what I watched through the glass. I backed off on the magnification and the direction appeared constant to me.

The spot I shoot in is basically shaped like a C. I shoot from the bottom to the top usually. The left side is mountainous with steep rocky faces and points. To the right its basically flat, with some natural rises and an old raised section for a defunct train track. The wind does tricky things there, but I like the challenge. I have had wind at my position be 180 degrees opposite of what it's doing at the target. I have watched it shift at the target but remain constant at my position. Maybe that's why the mirage looked odd?

 

[Deleted member 10043]

And sometimes mirage is so bad as to ground the rifle.

 

[Diver160651]

I realize that, but that is what I was seeing through the glass and checked the wind with my Kestrel and confirmed direction with a flag. I know it sounds messed up, but that is what I watched through the glass. I backed off on the magnification and the direction appeared constant to me.

The spot I shoot in is basically shaped like a C. I shoot from the bottom to the top usually. The left side is mountainous with steep rocky faces and points. To the right its basically flat, with some natural rises and an old raised section for a defunct train track. The wind does tricky things there, but I like the challenge. I have had wind at my position be 180 degrees opposite of what it's doing at the target. I have watched it shift at the target but remain constant at my position. Maybe that's why the mirage looked odd?

Shimmer will appear at whatever distance you focus your optic. If you have multiple wind zones, best (if you have time or want to fiddle around) to try running your focus on the spotter to reveal what’s happening across the board rather than just at the target or FFP.

 

[Precision Underground]

Last time we were out to distance I had to subtract .2-.3 mils by the time I got out to 1200+. I was running a new app and kept blaming it on that and then it dawned on me that it was likely mirage. The guys left and right of us confirmed they were shooting high all day as well.

Once corrected I tagged the 1930 yd 20x40 silhouette with 3 in a row. That was a new personal best for me and was incredibly satisfying because before the correction I sent about 10 rounds at it and saw absolutely nothing. I hate a no call and it gets me incredibly annoyed lol. I guess mirage had me holding .3 high and they were just sailing over it into neverland. What is .3 @1930? Something like 20in?

What do you think @Diver160651? Mirage the culprit here?

 

[Diver160651]

Honestly IDK, it could be external ballistics, range or maybe a combined effect of all three including shimmer. But that sounds a hair excessive solely to be shimmer if the target was still clearly defined. That is, unless you saw the target as very blurry due to the amount of Shimmer. Then ya, it could very well be.

The targets also appear larger in size and as a side note why reticle ranging ELR almost always ends up with a solution WAY to short.

One more of the optical distances that seem to show up in ELR is some sort of light refraction even when shimmer is NOT present. In the high desert where I have spent way too much time, it seems to happen after windy night, when the sun angles are really low, like early a.m. I “think” the particles can act a bit like water in the air, creating a similar effect to Snells. Once the sun angle changes, the dope comes back.. the weirdness here is that the target still looks sharp and I have no way of knowing it is present until it goes away in a hour or so. Lng story short I am just guessing as to the actual cause of the effect, but it does happen. Shimmer/AKA shooter mirage, is obvious, so even if I can't hit shit at least I know why .

 

[Bantam1]

Thank you for the info. I will play around with the focus next time I am out there. I was aware of the multiple wind angles and speeds. I didn't think about playing with the focus to check other zones. That makes more sense. Then I will experiment with holds to see how it's affecting what I see.

 

[Precision Underground]

Honestly IDK, it could be external ballistics, range or maybe a combined effect of all three including shimmer. But that sounds a hair excessive solely to be shimmer if the target was still clearly defined. That is, unless you saw the target as very blurry due to the amount of Shimmer. Then ya, it could very well be.

The targets also appear larger in size and as a side note why reticle ranging ELR almost always ends up with a solution WAY to short.

One more of the optical distances that seem to show up in ELR is some sort of light refraction even when shimmer is NOT present. In the high desert where I have spent way too much time, it seems to happen after windy night, when the sun angles are really low, like early a.m. I “think” the particles can act a bit like water in the air, creating a similar effect to Snells. Once the sun angle changes, the dope comes back.. the weirdness here is that the target still looks sharp and I have no way of knowing it is present until it goes away in a hour or so. Lng story short I am just guessing as to the actual cause of the effect, but it does happen. Shimmer/AKA shooter mirage, is obvious, so even if I can't hit shit at least I know why .

Target was *fairly clear. As clear as it can be in a FL summer anyway. It wasn’t straight boiling but there was def some mirage. I was noting that both seemingly experienced shooters left and right said their dope was high too. We should be heading back out soon and I’ll try to calculate .1-.2 for mirage and see if it lines up.

 

[Diver160651]

Target was *fairly clear. As clear as it can be in a FL summer anyway. It wasn’t straight boiling but there was def some mirage. I was noting that both seemingly experienced shooters left and right said their dope was high too. We should be heading back out soon and I’ll try to calculate .1-.2 for mirage and see if it lines up.

Seems like based on your description, it was optical. But I get spanked as well by stuff all the time, especially when traveling to new areas.

I wish there was a real way to account for the optical offsets as a good predictor rather than a bit corrective or guessing based on the image bounce..

 

[Back Spin]

Sometimes even when shooting on your home range weird stuff will come up as well.

Back in late April we had a sudden heat wave after much rain. The first 100 yards of my range was grass and from 100-200 yards it was dirt/gravel.

Around 11am I started to see a little mirage, but didn’t see much effect on my 100 yard zero. Come back at 3pm when it was much warmer and there was a little bit more mirage (but not to the point where the target image was dancing) along with 8-10 mph winds L to R. Shot groups at 200 yards and all 5 shooters on the line were hitting about .35 mil R, but elevation was spot on.

I came back in the evening to shoot a little more and checked my 100 yard zero and I was about .2 mil R. The offset persisted even when I tried to shoot from a higher position like from a bench or even a simulated rooftop.

I shot the next day early in the cool morning before the mirage picked up. 100 yard zero and 200 yard POI was back to normal. As the morning progressed, temps rose another 10 degrees and the mirage became noticeable. This time however there were only light winds. At 100 I saw my zero “shift” maybe .1 mil right. At 200 it was around .15 mil right and .15 low.

I’m not really sure what to make of those two shooting sessions other than it sucks to shoot through mirage! My observations seem to suggest that the optical distortion increases the farther out you shoot. Also, wind will play a factor in the distortion. But the offset due to mirage will be hard to measure once wind has a significant effect on the bullet itself.

 

[bassmaster07]

Target was *fairly clear. As clear as it can be in a FL summer anyway. It wasn’t straight boiling but there was def some mirage. I was noting that both seemingly experienced shooters left and right said their dope was high too. We should be heading back out soon and I’ll try to calculate .1-.2 for mirage and see if it lines up.

Shooting yesterday and a few weeks ago in Texas from 1pm-4pm with 90+ weather I was high too. Mirage makes since becuase it really showed up 400-600 yards. But then again I am just learning.

 

[Greg Langelius *]

I concentrate on the mirage image, and recall it mainly so I can recognize that type later.

I then shoot without any regard for the Mirage. After the string, I assess the POI vs POA aspect, and then make adjustment to bring it on target. The modified dope gets sorted away according to that mirage type. It's a memory game. Mirage can vary many ways.

Greg

 

[Currycure]

If you don't refocus your scope to the target, after looking at the closer distance mirage, you will have parallax that may significantly reduce the precision of your aiming.

 

[Greg Langelius *]

Good point...

 

[todd]

I seem to remember reading somewhere (The Wind Book for Rifle Shooters, perhaps?) that mirage will visually displace the appearance of the target in the direction the wind is blowing towards by both a vertical and horizontal component. I think there was a formula to figure it out, but I seem to recall that the "short version" answer was to make your POA the lower and 'into the wind' target appearance location.

I just found this article that addresses it a bit:

https://loadoutroom.com/12938/snipers-mirage-tip-week/

 

[Deleted member 113831]

If you are shooting in the same mirage band as the target, (e.g. flat range shooting from prone) then the target will displace up due to heat shimmer, making strike of the round appear high on the target.

If shooting from a different mirage band, (e.g. into a shaded valley, into a shaded area of a tree line) the image will displace in the direction of the warmer air.

Frank was correct on the podcast, (189 I think) that there is no way to accurately calculate the effect beforehand in the field. But I have seen 0.3mil (1 moa) change show up so often, that if I suspect the effect is there, that is my first guess.

All this assumes you zero'd in strong sunlight with low mirage to begin with.

If you have a true "light neutral" zero by zeroing in overcast conditions, or very early in the morning before the sun gets high, then there could be some cancellation going on that could mask what is actually happening.

In longrange riflery, trajectory is the pure science part. Gravity is a constant for our purposes.
Wind is in the art department.
Light is pure fucking voodoo.

 

[Hollywood 6mm]

In longrange riflery, trajectory is the pure science part. Gravity is a constant for our purposes.
Wind is in the art department.
Light is pure fucking voodoo.

I'm saving this quote and using it from now on with new shooters.

 

[j-huskey]

Nobody here is mentioning the optic used or the x factor.

A long time ago, with iron sights, at 1000 yards on the 45" bullseye, as it danced, you could find the center of the bounce in the mirage, and AMU taught you to "just shoot through it". We didn't lose a lot of shots.

And, then in early sniper world, with low x, we didnt lose that many shots either.

As the x went to 20-25, things not previously a problem appeared. Frank's podcast is about as good a starting place as any to start to learn.

Now......
Just for instance.... say, an 8'×8' steel plate at one mile... and a 375 ct.
And a drone on station.

With several people on glass looking, spotting, the drone will give you the most accurate splash report.

Have the spotter class recording "where they saw the splash" and the drone reader recording the actual splash, then compare what each is seeing.

Doing this on several x readings on variable power spotters or scopes, you "should" find a lower x that reduces the mirage loss effect, and increase your hits.

The visual effect on steel is going to change as the light changes due to refraction and distance. The target isnt moving, but the refraction issue makes your eye think it is. The brighter the steel color and the brighter the light, the more refraction as the mirage gets worse.

The old saw, light up, sight up, seems correct for iron sight shooting, but reversed for glass.

In the Hardrock matches, we see the high strikes every match with extreme light changes, and a lot of people not keeping dope books have a hard time eliminating the smaller fixable issues. The guys really not getting it are those on practice day who shoot early and have a solid zero, shooting the same gun 4 hours later and hitting a minute high.
It's a thinking game.

The next thing I'm not seeing any of you tell is the n/s/e/w orientation of your shooting ranges where you are seeing this problem.

Mil ranges by design are oriented north for a reason, even game camera manufacturers recommend orienting north to reduce the light effects on the camera sensors, to reduce camera error.

In the police sniper training on short ranges, having 4 ranges to move the class to, in 4 different directions, produces a half minute windage change by the n/s/e/w change alone. This mystifies the students early on, but data book records eventually show the evidence and teach the student something they need to know.

Since real world application does not allow north oriented every time, doing the 3/4 minute dot drills, in 4 directions with the same mechanical zero, keeping the strike consistently within a moa circle around the dot, gives the shooter confidence they can make the shot in the real world when they have to.

Increased distance increases the error movement. Incremental practice (increasing the distances) and good records generally show you what you need to know.

But. However. And all that, same rifle, same scope, and same lot of ammo, you dont learn much in these conditions when you change the rifle/scope/or ammo each session.

Food for thought guys.

 

[Bantam1]

This is the area I mostly shoot for longer range practice. I do not remember the exact azimuth, but its close to 350 or so if my memory is correct. The top down look doesn't show how steep some of the rock formations are. It is high desert with a little more brush cover than shown in this image. It must be an old shot from google. I like shooting here because the wind is tricky because of the bluffs and small canyons. There is a lot of wind shifting and swirling so it makes it challenging and allows me to shoot in different wind directions in one area.

 

[j-huskey]

@Bantam1

Curiosity q?
What's your known muzzle velocity with that ammunition lot, and what's the program say the velocity is at 1400 yards (with corrected DA) ?

Second curiosity q?
Bullet angle of approach at 1400 in the trajectory curve (if you know)?

 

[Bantam1]

I would have to look it up when I get home because I'm at work today. I was shooting factory Hornady 140 ELD-M. Magnetospeed said 2650ish but according to correction it was more like 2712. I just punched it in to Strelok and it's saying 15.7 mils which was about where I was, I think it was 16.0. when the rifle was new It only needed 14.7 in the winter to get to 1400. If I remember correctly velocity was around 1150 or so at the target.

The angle I have no idea. I am not sure how to check that. I only have about 4-5 degrees up on the gun while shooting there.

I'll be testing again with my loads the next time I get out there.

 

[Back Spin]

@j-huskey When I saw the effect I was shooting north. Magnification was at most 18x (Bushnell LRHS) but I believe I also saw the effects on lower magnification during the initial afternoon shooting session.

With the wind and setting sun, my shots were pushed in the direction of the wind. I had not previously seen a direct correlation of the direction of light and POI (but keep in mind I almost always shoot northward).

The next morning, with almost no wind, I was able to shoot at a 2 inch square at 200 yards in a no mirage and then heavy mirage condition. The no mirage shot was my cold bore which went toward the top of the square (which was a similar POI for my previous 100 yard cold bore shots).

I took 2 shots through mirage: one shot hit fairly center and the other was low on the square. The mean between those 2 shots was about .2 mil lower than my cold bore, but I realize mirage may not be the primary cause of that.

 

[j-huskey]

@Bantam1

Fyi. Group of us here are working toward going to King of 2 Miles, and playing with several things. And willing to share information even though it might not be conventional thought, however, food for thought.

Couple of things. Beach shelter pop up 10x10, shooting table, honda inverter generator and a couple of box fans. All trying to make us more comfortable and reduce barrel mirage seen by the shooter. Call us bums..?

Have used drone to verify strikes and that became critical when using solids, but, the drone gives us wind conditions we will miss with the eye flying to station, and on station, the drone movement will warn of missed seen gusts.

All this information is for process of elimination.

Looking at possibilities, since your rifle load is hammering at 1000, figuring 2600 min muzzle and 2700 max muzzle, your load is playing in the area of transonic at 1400. This is a possible explanation of "some" of your vertical.
In that zone, a 4oclock to 10oclock 5+ mph gusts can raise the strike up and left, inverse a 7-2, up and right. We have had this happen to us testing our junk.

** It does not sound like that is your issue, once you described correcting DA and getting back on. Unless you have some sneaking 6-12 gusts catching you in the edge of transonic.

So, going back to the simplest solution is generally the correct solution, it sounds like mirage, both barrel and downrange, and a bit of tired eye on his part.

Be real curious to eliminate edge of transonic and missed gusts, if you had similar good results like at 1000 at 1200 or 1300, and then see them starting at 1400.

Again, your correcting DA and getting back on points strongly to the mirage deal.

Doing all the other stuff mentioned will just either verify these things or help you catch a missed error at a closer range. Either way, it gives some more data and experiences that help you get better.

Just more food for thought. Hope there is a small bite there that helps some.

 

[Bantam1]

I'll be going back out with my new loads that are exceeding 2800fps. I want to see if this will help. The closest range I have to home is only 600, but it allows me to at least confirm velocity.

I'll report back once I get out again and test at 1000-1400+.

I appreciate the input and knowledge you have shared. Good luck at KO2M!

 

[j-huskey]

@j-huskey When I saw the effect I was shooting north. Magnification was at most 18x (Bushnell LRHS) but I believe I also saw the effects on lower magnification during the initial afternoon shooting session.

With the wind and setting sun, my shots were pushed in the direction of the wind. I had not previously seen a direct correlation of the direction of light and POI (but keep in mind I almost always shoot northward).

The next morning, with almost no wind, I was able to shoot at a 2 inch square at 200 yards in a no mirage and then heavy mirage condition. The no mirage shot was my cold bore which went toward the top of the square (which was a similar POI for my previous 100 yard cold bore shots).

I took 2 shots through mirage: one shot hit fairly center and the other was low on the square. The mean between those 2 shots was about .2 mil lower than my cold bore, but I realize mirage may not be the primary cause of that.

I can think of several things besides mirage to cause the shift, very small things.

Recoil innoculation.

Recoil moving you just enough to disturb npa and a small scope shadow missed during concentration toward the next shot.

If bipod used, surface, grass, gravel, or dirt, changed recoil impulse against your body. Doesnt take much.

Have started in morning with shirt on, went to long sleeve tee and elbow pads, and got changed poi.

*** lots and lots of ifs. Lots. If I watched you shoot say a year, like I have with my crew, I could probably get it right on the 3rd guess.

I dont like to second guess my guys less than 6 months of training sessions. As a group in 6 months we normally find the right answer, and feel real dumb for not seeing it sooner. Jmhe

 

[Bantam1]

I know there are many variables, but shooting at this same area for many years and seeing the heavy mirage made me raise the question as this was a little new to me. I typically fish offshore in the summer and shoot the other months. I have shot with mirage before, but nothing like this and the added heat coming off the barrel making it worse.

I'm shooting prone off a mat with the TBAC bipod in the dirt, rear bag supported. The rifle weighs 18-19 pounds and has a break. There is very little recoil. I load the bipod and keep the rifle in my shoulder and feel very comfortable. I don't feel like I am fighting anything. My trigger finger is straight and I follow through when I break the shot. I'm also a large mammal at 6'3" 260 pounds.

I learned to shoot longer range using my 308 with no break and worked on my fundamentals over the years. I measured and recorded the results showing improvements. I like to think my fundamentals are good, but I am no expert. I'm sure I could use more instruction and hope to attend a class next year. I realize I am not perfect and I'm sure there are many things I could be missing in my shooting abilities.

 

[Diver160651]

As said early on in the thread:
The wind moves the heat shimmer and the target (appears to) grows “mostly” in the direction of wind and bounces back home.. of course, some winds like head/tail and the images can grow in all three directions. Or even have shimmer at 180° (opposing winds - because of ground effects) vrs the wind felt at the FFP..

The optical stuff is just weird. One of the weird ones I've seen this a few times and again this weekend @ a bit over 1900y, as the wind clocked the target image cleaned up but literally wobbled rapidly back and forth, I mean like full scale acid trip.. looked like the plate was bending and twisting in the spotter.. It appeared about 30% larger, then suddenly, back to a L-R heat shimmer (you guys are calling mirage).

For what it is worth we had our ranges at 90° to each other with almost the same FFP location and 12 shooters.. We often shoot in opposing directions as well. I am sorry but after many many years of ELR, all I can say is there is no way to accurately tell how much displacement you have. Add in all the other noise, offsets, wind, dust in the air acting a bit like water and refracting the images at low sun angles and your first shot is going to be what it is or your dope may appear a couple of 1/10ths different.​

Worth repeating I don't think you guys are often seeing Mirage, but rather heat haze AKA heat shimmer. Classic desert mirage (inferior) you'll see the classic water and 2 targets with the reflected one lower.

Over water or snow you could see the opposite with the target Floating in the air and upside down. But both types of the Mirage over natural terrain (not black asphalt) are usually occurring further than most are setting their targets.


One more important note: When shooting across relatively flat terrain, the lower you are, the worse the heat shimmer will appear. Get up from prone to a bench height and images can clear up significantly. You can further reduce the heat induced haze or shimmer if you can shoot from an elevated FFP or to an elevated target; better yet across a valley doing both

the added heat coming off the barrel making it worse.

If your getting the heat haze off your barrel, on top of the target stuff.. it is going to be really tough and it really is time to let it cool, blow on top of the barrel and shoot quickly or possible use a heat shield.

For ELR, like @Skookum said ......

 

[Bantam1]

I finally made it back out to my desert long range spot to shoot in the heat. I had my barrel cerakoted to see if that helped with the heat waves coming off the barrel, and it seemed to help over bead blasted stainless it used to be. I brought an easy up to try shooting from the shade vs. shooting in the sun. 98 degrees, 20% Humidity, 4000DA.

My 1400 yard dope called for 12.8 Mils and I was not able to connect. I have verified my dope and I know for sure if was image shift from the heat or mirage. I ended up holding at the bottom edge of the plate and my impacts were 18" high.

I tried to dial down .2 and my impacts were still high, so I know it is a shift in the image from the heat and/or wind. The wind was extra shifty and gusting/ dropping so I am not sure how much was wind jump. I had full value wind from either direction and speeds from 3-18mph. Sometimes I would get 1/4 value wind, then a slight head wind at my face, but 3:00/9:00 at the target.

From 1000-1200 I had no issues making my wind calls and making my hits. Once I got to 1400 and shooting in the sun all bets were off. It was frustrating, but I learned a little I think. I thought I had it figured out and like Skookum said it's pure fucking voodoo. I do appreciate all the input you guys gave me earlier. It pointed me in the right direction and helped me determine what was going on.

Full image of the target from a previous trip verifying my loads at distance and wind performance (still learning). Torso size 18" Wide x 20" tall. Head is 6 x 6"

 

[DellaDog]

I know with my 6.5 CM, 1000-1300 is usually fairly easy w/ 140 Hybrids at 2800.
1400 is where issues begin.
I'll bet you're transonic in that range and weird crap happens unrelated to wind and mirage.

Just a thought.

 

[Bantam1]

My 135 A-Tip load is going 2900 and it is super to 1480 or something like that, well on that days condition. It is around 1320-1350 at that distance I think.

With the 140 ELD yes I completely agree. My load is 2800 or so with the 140. They seem to be pretty stable when I shoot them in cooler weather out there even to 1400. Drop is 14.6 mil at 1400.

 

[_Raining]

I have no advise for reading mirage caused by external environmentals but the original post seemed to indicate the problem was from barrel heat which you can combat with a mirage shield/band that you see on F Class and BR rifles.

 

[Deleted member 113831]

Went to a class a couple weeks ago...

First day verifying zero, my zero was 0.2 mils low and 0.2 mils right. (Bright sun coming from 7:30 O'clock at 9am, 27.54 inHG, 70*F,)

My zero was dead on at my home range a few days prior to the class. (Heavy overcast, 28.1 inHG, 70*F)

The class was only a short few hours drive from my home, so no airline can be blamed for the shift.
A change of only 0.5 inHg cannot be to blame.
The only real change was light.

I shot the entire first day (out to 1100 yds) adding 0.2 mils to my elevation, and I dialed out the windage change.
The second day, the wind from the right was strong enough that the vertical effect of side wind was canceling out the difference, so I dialed true dope.

I get home to verify zero w/same ammo taken to the class (again, heavy overcast), dead nuts on.

 

[PracticalTactical]

Mirage certainly displaces the image.

Here's a video showing the target image dancing around and this is on a clam but warm day.



If you ever attend F Class events you can watch the effect of sun light on scores when there is a mix of sun and clouds. Guys will beat the center up with a cloud over head, then it passes and sun comes over the range, then everyone starts dropping points out the bottom.

After a shot or two they adjust and get back to center, but that's only until the next cloud rolls in. That's when they start shooting high.

Guys who get it, adjust when they see the light change and don't drop points. Guys who don't get it, walk off the line wondering why they were getting verticals.

Often times they attribute the problem to funky loads.

Another error is often made when light picks up because it makes mirage more visible. Guys will often interpret that as increased wind speed and hold into the wind more. That will drop points too. In this case the wind did not change, but some guys thought it did. You need to understand what mirage looks like in different light levels and not fall for such light changes.

 

[Deleted member 10043]

Yep, good marksmanship. Follow the bullet and don't sweat it.

 

[sinister]

Try using a mirage band.

 

[PracticalTactical]

The mirage band will help with barrel heat, but not the air between you and the target.

Lots of guys use velcro tape and a strip of a vertical blind.

 

[Bantam1]

I ended up Cerakoting the barrel and it helped a lot compared to the bead blasted stainless when in the sun. The last trip out I brought an easy-up to stay out of the sun. 110+ in the desert sun sucks. I had no mirage effects from the barrel heat but the blurry air between myself and the target made it challenging. I'll end up making a vertical blind band at some point, although I would rather not go out there in the hot summer.

I have my dope verified at the same location with multiple DA's and weather conditions now. It's just the image distortion I'm chasing and I figured it out on the last couple of trips. It's not consistent and it varies by the amount of mirage/light. I just have to adjust based on what the bullet shows me. Thankfully I have less misses now since I have been tracking it and trying to learn what I'm really seeing with the environmental effects. I take good notes and I'm getting first round impacts on the plate. They just may be high or low until I figure out the image shift that day or hour.

 

[PracticalTactical]

I ended up Cerakoting the barrel and it helped a lot compared to the bead blasted stainless when in the sun. The last trip out I brought an easy-up to stay out of the sun. 110+ in the desert sun sucks. I had no mirage effects from the barrel heat but the blurry air between myself and the target made it challenging. I'll end up making a vertical blind band at some point, although I would rather not go out there in the hot summer.

I have my dope verified at the same location with multiple DA's and weather conditions now. It's just the image distortion I'm chasing and I figured it out on the last couple of trips. It's not consistent and it varies by the amount of mirage/light. I just have to adjust based on what the bullet shows me. Thankfully I have less misses now since I have been tracking it and trying to learn what I'm really seeing with the environmental effects. I take good notes and I'm getting first round impacts on the plate. They just may be high or low until I figure out the image shift that day or hour.

You could try to keep track of the direction you are shooting relative to the position of the sun.

The lights up, sights up scenario assumes the sun is directly above the target.

In reality the refraction will occur either toward or away from the sun. If the sun is at 2 o'clock, the refraction will be more on a 2 to 8 line and not 12 to 6.

Some log sheets have a circle with a dot in the center where you draw a line indicating the direction of the sun... and brightness level.

It's a good exercise, but might take some of the fun out of it depending on how convenient it all is for you.

I don't recall the over all effect to ever be more than about 1 MOA in total from direct sun to dark cloud cover.

 

[Bantam1]

I shoot at the same area in the same direction every time. The sun changes a little throughout the season, but for the most part it is in the same direction to me. I record it in my data book along with brightness/time of day.

I think the majority of my issue was refraction from the heat waves and not so much light issues. I need to go back out there again but it's been too hot to go shoot a few rounds and go home. The drive time, set up time and the heat makes it not worth it right now. The guys I shoot with are all either afraid of the heat or prepping for deer season next month. They have no desire to go.

I do appreciate the info from all of you. I enjoy learning and you guys help shorten the learning curve for me.

 

[Marine52]

This article by the South Texas Marksmanship Training Center (STMTC) is the best Ive seen on the issue of visual target displacement from mirage. Does not address “reading mirage” for wind‘s impact on bullet path.

South Texas Marksmanship Training Center - Reading Mirage