Stupid mirage question

[pitdog85]

So I normally shoot around 600-700m always in heavy mirage. I have the mirage fairly worked out At this distance I need to add 0.2-0.3mil more than the calculator calls for to get hits on the centreline in this heavy mirage.

So today I put some milk bottles at 350m along with my plate at 600m. I decide to shoot the milk bottles first and sure enough 3 misses straight up can't tell if they are high low left or right. I'm thinking what the heck is wrong with me so I go out to 600m first impact right edge make a correction put the next to within 2 inches of centre dialling an extra 0.2mil over what calculator called for.

So back to the milk bottles I go I take another two shots and miss both. I go to check the milk bottles which are filled with coloured water and I actually hit one high but that's it.

My question is if at a given distance In my case 600m I need 0.2mil extra to get centreline hits if I go back to 350 in the same conditions should I still need to dial an extra 0.2-0.3mil or would it Be less because I'm now closer. What if I went to 1000m would I still likely need the 0.2-0.3mil extra or would it Be more because of the increased distance?? I'm not sure if I'm very clear what I'm asking is should my mirage correction work with mils ie 0.2mil correction holds for all distances or do mirage corrections get more or less depending on whether target is closer or further?

Thanks

 

[Diver160651]

Unless you have a temp inversion, usually the image displacement from mirage is up (meaning you are actually aiming up) but is completely condition dependent. Usually with mirage the lower you are to the ground, the flatter the surface and further the distances the worse the optical disturbances.

Bent light from low winter sun angles rather than heat induced mirage or shimmer, is another issue altogether, but posses a similar issue. I have not seen a formula that works.

I’ve seen desert dust in the air in the early am light when shooting easterly, do some weird stuff to my aiming when shooting ELR and I am not 100% sure I can even tell the effect of we’re the true image is until I’ve fired a round.

 

[Deleted member 113831]

You are probably dealing with 2 different mirage conditions. I'm guessing that the ground between you and the 350m target is fairly flat and featureless. What does the ground between the 350m and the 700m look like? Are there are any slightly elevated terrain features (to include vegetation)?

If so, then what you are likely getting is a lensing effect at the further distances, that doesn't apply to the shorter distance. So when you make that adjustment at longer range, you are too high at the shorter.

What @Diver160651 says is true, mirage will usually carry the image in the direction of the mirage. However, that is only true if the shooter and the target are both located within the same mirage condition.

If there is anything that sets up an independent thermal interface between you and the target, then the target will optically deflect toward the direction of the warmer air. If you shoot from and elevated position above these interfaces, you will see the effect disappear.

 

[RTH1800]

Agree with above.
In addition, there is a reason people who want to learn shoot paper targets. It seems frowned upon today, but "banging 3 MOA steel" is an imprecise activity. It is unfortunate that it has become the norm. So much can be learned from knowing your exact POI based off of a nearly exact POA. Once you get that, shoot whatever you like. Until you get that, you are simply wasting ammunition.

 

[Diver160651]

Agree with above.
In addition, there is a reason people who want to learn shoot paper targets. It seems frowned upon today, but "banging 3 MOA steel" is an imprecise activity. It is unfortunate that it has become the norm. So much can be learned from knowing your exact POI based of a nearly exact POA. Once you get that, shoot whatever you like. Until you get that, you are simply wasting ammunition.

Ya, I get your point. For fine BC tuning I actually always use paper. I'll even go so far as to say, this is especially true of benchrest guys who shoot lost of rounds of mechanical rests for years under only a handful of ranges, are maybe the best tuned to mirage under their particular ranges, they also use sighters to correct.

But to be fair, a lot of people using steel, paint it up and easily see their water marks. Something NOT seen at most square ranges where you'll use paper, is like I mentioned in my post. Mirage inversion from slopes (although snow with warm spring air can do almost the same), but primarily bent light issues when shooting directly into low angle Sun with crap in the air to refract the light. I have never seen a major paper range set up to shoot anywhere near directly into the morning sun. I am not saying that there aren't a few somewhere, but I am saying that I would not under play the importance of field shooters experiences in regards to optical disturbances.

 

[RTH1800]

You are likley correct for commericial or public ranges. I do not shoot on them. I set mine up on my land. I do admit that I seldom shoot directly into the sun. Cannot learn much shooting what you are struggling to see. I do shoot paper across snow, rivers, ravines, lakes etc. It can be a humbling experience.

 

[pitdog85]

Thanks guys where I shoot is completely flat I shoot prone so scope is less than 30cm from grass. I'm gunna chalk up the misses due to windage calls and try next time. For me if I don't correct for mirage here I will shoot low everytime at 600m calculator calls for 4.1mil with My environmental and velocity but I will dial 4.3mil and hits will hold good vertical along centreline of plate.

 

[Deleted member 113831]

My question is if at a given distance In my case 600m I need 0.2mil extra to get centreline hits if I go back to 350 in the same conditions should I still need to dial an extra 0.2-0.3mil or would it Be less because I'm now closer. What if I went to 1000m would I still likely need the 0.2-0.3mil extra or would it Be more because of the increased distance?? I'm not sure if I'm very clear what I'm asking is should my mirage correction work with mils ie 0.2mil correction holds for all distances or do mirage corrections get more or less depending on whether target is closer or further?

Thanks

This part is hard to answer. It is a solid "it depends".

If all the targets are within the same mirage condition, then they will all be affected the same 0.2-.03mil optical displacement. However, if there are differing mirage conditions the further you go out caused by terrain features like a ridge, or a valley, or body of water, or shadow of a hill, then all bets are off.

 

[Diver160651]

Thanks guys where I shoot is completely flat I shoot prone so scope is less than 30cm from grass. I'm gunna chalk up the misses due to windage calls and try next time. For me if I don't correct for mirage here I will shoot low everytime at 600m calculator calls for 4.1mil with My environmental and velocity but I will dial 4.3mil and hits will hold good vertical along centreline of plate.

Note that often what shooters call mirage is NOT pure mirage, but “shimmer”.

Shimmer is more what we use to see the wind direction, but most of us use the name “mirage” for both. I do the same, but just wanted to point that out.

The result of most shimmer conditions causes the image to appear higher, and thus we are aiming higher in error.

Wind will move the shimmer/mirage L/R but must of use just loose that optical part in with our wind call.

Pure mirage, inferior and superior and make the image appear lower or higher. Superior mirage is the “inversion” I mentioned like shooting over snow with really warm air above it.

I think most shooters encounter conditions that the refraction is seen in the form of shimmer. Shooters referer to it as boiling or running L/R and use it for wind calls.

In most shooting conditions, where most people have ranges and are seeing shimmering, the images will appear higher and will use less come-ups not more.

To add more confusion, there are other things like I mentioned that also cause refraction like dirt in the air and low sun angles.

Btw all this is what makes mil-ranging small objects far away very inaccurate. Because the images are fuzzy and appear larger.

I guess point is we need to know what we’re looking at before we assume we need to add elevation to our scopes, most often, that would be the wrong call.