Mirage

[BOB LEE SWAGGER]

Talk to me like I'm an idiot. How do you know if the mirage that you see in your scope view is coming from your barrel or at your target or both?

 

[barefooter56]

Talk to me like I'm an idiot. How do you know if the mirage that you see in your scope view is coming from your barrel or at your target or both?

Bob Lee,
Build or buy a good mirage shade for your barrel to test and see whats what. If you are target shooting its probably both due to the barrel heat.
Take care,

 

[BoydAllen]

The way that you tell if you are looking through barrel mirage is to place something over the barrel (target, towel, etc.) while looking through the scope. If the image improves , you have barrrel mirage. I have done this for a number of fellows, who were not competitors and even though the target image was greatly improved, I found that the whole thing then became about what seemed to be their reservations about doing anything that looked "different" given that they had never been to a benchrest match to see how common barrel mirage shields are in in competition. If the wind is above a certain level, barrel mirage will be blown away before it gets to your field of view. The same is true of mirage between you and the target.

Do you know what causes mirage? If not we need to deal with that. Also, what power scope are you using?

 

[BoydAllen]

When the ground is warmer than the air above it, it heats the air that is in contact with it, and that makes that air less dense (lighter) so it rises through the slightly cooler air that is above it. My imagining of this is that the hot air comes up through the cooler air in "bubbles". The warmer, less dense air does not bend light the same as denser air. It has a slightly different refractive index. This is why the target appears to move around when there is mirage. As different densities of air come into the field of view, the image is displaced by different amount depending on the refractive index of what is momentarily in the field of view, and in a particular part of the field of view. Generally, the target image is displace in the direction of of air movement. In that sense, mirage is the last wind flag before the target. The tricky part is that not only does the bullet go with the wind, but if your aim point will be moved in that direction increasing the effect beyond what the wind alone would produce. The most extreme mirage happens when the sun is shining and there is a momentary stop of the wind. This produces what is referred to as a boil, because the target appears as if it is behind boiling water, and the direction of target movement is straight up. Generally, this is not a good time to shoot, unless you know that the condition is returning fairly often, and your equipment allows you to aim without touching the rifle when there is less mirage (more wind) and shoot when there is more (less wind). Most rifles are not able to be shot this way because of recoil, trigger weight, stock design, rifle balance, and rest/bag design...bit if your rifle is, and you are seeing those conditions, it is worth experimenting with. At this point, rather than continue with this book, I think that it would be better to answer questions, but first one from me. What power scope are you shooting? The reason that I ask is that below a certain power target mirage is hard to see.

 

[BOB LEE SWAGGER]

I use both a NF comp & a NXS 12 X 42. I am almost always above 30 power. In FL as well.

 

[riverwolf1]

Interesting reading.
http://southtexasshooting.org/multimedia/text/mirage.html

 

[ZenArchery]

The wind will push the mirage. So stand up. If you feel it in your face it is coming forward. If you feel it from behind its from behind.

 

[JFM33]

I use a spotting scope for the mirage .When I focuse at the target and then back the distance in and look just above the ground.
The Mirage is my friend ,except when it's cloudy.

 

[4xforfun]

Take a big assed breath and blow down the length of your bbl while you look through the scope. if it changes/goes away it is BBL mirage. Also, BBL mirage doesn't look anything like regular mirage. BBl mirage looks like a blurry mess...like you are looking through dirty cling wrap. You can change your parelex adjustment and see the change in true mirage.

Also, if there is any measurable wind bbl mirage shouldn't be much of a problem.

Tod

 

[Eric Leonard]

I shot 2 UBR targets at 100 yards at about 1pm today and the crosshair in my 35xLCS was bouncing in the 8 ring in ever direction,,I had a slight head wind or a boil and it was really tough,,shot a 62 and a 64,,I think I would rather have 25 mph winds than that boil,,

 

[Lapua40X]

Take a big assed breath and blow down the length of your bbl while you look through the scope. if it changes/goes away it is BBL mirage. Also, BBL mirage doesn't look anything like regular mirage. BBl mirage looks like a blurry mess...like you are looking through dirty cling wrap. You can change your parelex adjustment and see the change in true mirage.

Also, if there is any measurable wind bbl mirage shouldn't be much of a problem.

Tod

Yup - it ain't rocket science.

 

[BOB LEE SWAGGER]

Yup - it ain't rocket science.

Propulsion, trajectory, stability, atmospheric forces...

 

[savagedasher]

Very seldom in Florida I get above 35 power .
Many of times at 1000 yards in the summer you have to wate for the marige to clear to see the target. We Had shoot that had 50" .
Larry

 

[Lightload]

Propulsion, trajectory, stability, atmospheric forces...

Wait.....ain't that Rocket.Science?

 

[Lapua40X]

Propulsion, trajectory, stability, atmospheric forces...

Wait.....ain't that Rocket.Science?

Yes, of course. Excellent sedgeway if you want to make the transition in the discussion from an atmospheric phenomenon to unrelated laws of motion. But mirage is an atmospheric refraction that is dependent upon air density and temperature. Toss in a bit of wind and it can really complicate matters.
I guess we'd need to invite Newton and Galileo to the forum if we wanted to broaden the discussion.