45x scopes & mirage.

R

russell m

Guest
I am using a 36 x leaupold. I have my first match tomorrow. It is a score match. I am suprisingly calm. I have practacing the last 3 weekends shooting at the dot. With my 36x scope & a small amount of mirage the dot is hard to see. So I can see why a higher power scope is needed. But on the other hand when the scope has more power doesnt it make the mirage look worse.

The second ? is. How to shoot in real bad mirage. I have been told to wait & let the conditions blow the mirage out & then put my crosshairs on the dot. If I do this & there is no wind everything is good. If I have a right left wind & I wait for what I am assuming is the wind to blow the mirage out but never does & I am running out of time. Are ther any Aids to help me with the mirage? Such as the 2 laminated wind charts that I keep in my loading box that someone from BRC posted for me that helps me with the wind. So I get my gun on target as best possible & then the wind switches left to right,the moth ball is trying to jump out of my field of view. Let alone trying to see the dot. So this is where a good windage top comes into play. I would dial in some left windage & hope for the best. Is there any thing other than trigger time that helps in mirage.
I hope I didnt confuse anyone. Any help would be appreciated.
russell m
 
Go to the sighter

Shoot one where you think it autta go and see what happens. You can go from there. There are a number of theories as to what mirage is but it for sure has force. That must be compensated for.
 
Thanks Nader for the encouragement.
I shoot every weekend & sometimes after work. I know all of the good shooters on here did not get there overnight. I hope to someday think I am a good shooter & be able to take home some wood.
I have just ordered a kreiger barrel from Beggs with tuner.

Do you know if mirage gets worse with more magnification such as going from 36 to 45x. I am considering getting a booster,having the scope frozen & getting new scope mounts.
russell m
 
Nader
MY gun was buit by Larry Smart. It is a Panda action,Kelbly rings,Jewel Trigger,Shillen barrel, McClain stock. The action is a 1993. So I am assuming the gun has been around a while. I bought it used. I did a search on Larry Smart on BRC & read several post about him in the 80's. He was regarded a a very good gun smith.
russell m
 
I am still a novis at BR, but I did shoot High Power. I would try when you have mirage to note which angle and which direction it is. Then aim at the practice dot and see where the bullet hole is. Then while the mirage is the same offset your aim to adjust where your bullet will go on your score target. You may not hit the dot every time, but this should keep you in the 10 ring.

This has helped me very much along with waiting for the wind to calm.

"Aim small miss small", :D

gt40
 
Visually - -

Nader said:
Do you know if mirage gets worse with more magnification such as going from 36 to 45x. I am considering getting a booster,having the scope frozen & getting new scope mounts.
russell m
Click to expand...
Russell,if you can't see it you can't deal with it!(Booster---No)(Frozen scope---No)mounts? maybe-What action do you shoot,what mounts?
joel[/QUOTE]

Mirage seems worse with higher magnification. I shoot mostly 6 power and mirage is not so notiable but can be seen.

As I stated earlier, Mirage is a real force, not just a visual distortion. Mirage will push your bullets. There are those I think who do not think there is force to mirage but there is. We who can't see it sure do pay for it being there sometimes ! :eek:
 
Correct me if I am wrong here but mirage is purely an optical ocurrence. It is the result of bending light rays making the image appear to move, just like heat shimmer on a hot road. If you shot every round when the apparent image was in a different place you'd have a big group, if you shot every round (by luck) when the apparent image was in the same place you'd shoot a small group.

Lets assume you had a dead still day (I mean theoretically no wind at all) and horrific mirage shooting a really reliable rail that always returned to a perfect hold. The image and crosshairs may look like they are all over the place but a nice group would be shot with the mirage having no effect on the accuracy.

The movement of mirage is from the wind moving the hot air and you can only see it at the distance the scope is focussed at.

http://en.wikipedia.org/wiki/Mirage

What am I missing here ??

Bryce
 
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BJS6

Your assumptions are substantially correct.

I have done your Rail Gun experiment and at 300 yards or less with near zero wind it is true that group size will remain nearly constant with or without visible mirage effects.

However, with the same Rail Gun setup at 600 yards with near zero wind, the groups shot with severe visible mirage effects showed slightly more vertical dispersion than those shot with no visible mirage effects.

The visible effects we call mirage are due to the refraction (bending) of the light path from distant images and in turn this due to the variation in density of the air in the light path. Therefore the intensity of the visible mirage effect relates to the degree of variance of the air density. Variance in the air density along the path of the bullet will cause a variance in the aerodynamic drag retarding the bullet flight.

Since at longer ranges, the bullet path must of necessity pass through more horizontal and also more vertical arc and for a longer time it would seem probable that it would be more subject to the variances of drag than at shorter ranges. IMHO the added time and path length due to the higher arc is why the long range case with mirage (air density gradient) begins to show some more detectable vertical dispersion than at shorter ranges.

Adding wind to the test makes for more difficult analysis. However, the rail gun group sizes show the same tendencies but with the addition of horizontal group dispersion proportional to the horizontal wind component but substantially independent of the amount of visible mirage.

Nothing helps learn the effects of wind and mirage like being able to shoot with a rail gun. I must try to budget for one of my own.
 
Well I just got home from my 1st match at the Tomball Club. I achieved my goal & that was not to come in last place. Mirage was not an issue today. Condition were good with cloud cover. I did hear someone talking about mirage. How it is morer that an illusion it can actually move my bullet. I havent shot enough to determine my own conclusion.
Thanks for all the input. By the way Nader my stick is a McMillan.
russell m
 
My experience with Mirage

Has been that there actually is some upward force to mirage. I believe it to be evaporation; moist air rising. I realize there is some optical distortion to the puzzle but there is force to it. If your flsgsd show no wind ata ll and there is heavy mirage you will get verticle, even if you wait for a hole in the mirage to sight by. It also moves the bullet @ angles; the angle it is running in , if it is running at an angle.

Rather or not there is force probably isn't necessary to discuss but if the result of whatever it is actiong on your sight picture/ bullet movement, one better allow for it. I remain convinced that evaporation does indeed have force.
 
at some matches you have mirage stripes between targets; sometimes useful... anyway: shooting in mirage is a bad thing: check the sky: maybe a cloud is coming that's worth waiting for.
I'm not that keen on shooting at a target that seems to be at different places (moving) at all times, you really can see what way the wind will move your bullet, but so do your flags!
mirage makes you wish you had a variable scope on the rig
 
Mirage Question

I am reading this thread with some interest as mirage has been tough for me to figure out and compensate for.

I think that I'm reading that there is agreement that mirage is thermally induced condition?

If that is the case, I think Pete Wass' analysis that mirage has physical attributes, as well as optical, is valid.

I began thinking about soaring birds and gliders using thermals. That would suggest to me that there is more physical properties, less dense (more dense), rising etc.

This not an attempt to hijack this thread into one of aviation priciples, but, instead a way for me to relate the mirage topic into application during shooting sessions.

Thanks
 
Optical and physical

The physical effect can be seen optically - the two are not separate. A simple method for dealing with mirage is to watch the flags primarily and use the mirage "flow" as a double check of the condition. Given a decision that the desired condition exists, pick a position of the aiming point and use that one throughout the target. To further explain, if the aiming point is jumping up and down, aim at the up or aim at the down. Actually, if you were aiming at the down and the target jumps up you can still shoot if you don't follow the target.

The primary use of flags is necessary because the mirage you see is only within the depth of field of your scope. When the flags are going one way and the mirage another you are seeing mirage where no flag is placed. Mirage is as much useful as it is a problem so long as you understand what you see.
 
I'm a beginner as well, but fundamentally, the mirage SHOULD have a physical force to it. As stated, with a certain range it probably won't matter. But the mirage is the result of heat rising, and that rising does create a small upward force.
 
it's absolutely certain that the target does not move; the hot air makes it dance in your scope, if you can aim at the exact spot all the shots; your in, I usually don't know when to shoot; the bull seems to dance too fast for my slow mind, so with the high magnification, I try to look at aiming points along my crosshair as not to focus on the cross; sometimes it works fine.
 
As I said earlier

Most of the time I can not see mirage throuh my 6 power scopes, therefore one needs to look for it elsewhere and usually through a spotting scope. The targets do not jump looking through a 6 power scope, most of the time.

It is only reasonable that thurmals do have force; like someone else mentioned, otherwise not only birds but gliders could not stay up! I have experienced this force a number of times while piloting an airplane. Some of em will take you WAAAAY UP there.

Perhaps rail gunners are able to shoot through the thurmals but, form my experience, my rifles will not shoot through it. Even though it does not appear to my eye, it moves me bullets all the same.

A simple way to prove this is to shoot in a straight up boil on a day when it is intimertently cloudy. Set your dot on the center of the "moth ball" when the mirage is down and don't move it. Wait for the sun and the boil. Shoot and see where the bullet goes. 10 times outta 9 it will be up way more than one wants it to be.
 
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It just occured to me - -

perhaps the reason a rail gun can shoot through mirage is that the group will form in any given condition so shooting in an updraft wouldn't have any effect on the group as long as the shots were shot quickly. Try hitting dots on a score target and see if there isn't some movement.
 
Thanks every one. You all have helped me tremendously.

Wilbur
I will try what you suggested aim at the same spot be it on the up or down movement. This seems like it should help. Instead of chasing the mothball.
russell m
 
Maybe when shooting 100/200 benchrest the rail doesn't show enlarged groups due to mirage simply because the mirage isn't a very significant factor when you are not relying on your optics to reset the rifle for the next shot.

Peter, sorry but I can't help but think you are overstating the actual physical effect on the bullet due to rising air currents associated with mirage. What effective "wind strength" does the moving mass of air create and how far will that slow moving air shift the bullet ? The air movement upwards that logically goes hand in hand with mirage certainly isn't enough to make a flag tail move if there was no other wind.

It seems to me that the biggest aspect that a rail removes when shooting in heavy mirage is the re-aiming, take that out of the shooting process and the groups stay small. I don't think that is coincidental and the small groups are a by product of some other factor like shooting fast. If that was the case the results that these guys report wouldn't be reliable or consistent, miss a "rise" due to mirage and you'd still have a high shot just like if they missed a wind shift. If they are not using the scope and instead are sitting up watching the flags how do they pay attention to the mirage to not get bitten by the upwards thermals that you are describing ?

Bad mirage that isn't read correctly essentially gives you an aim with each shot the is different every time, like if somebody randomly gave the scope a click or two here and there. The fact that you can't see the mirage with the 6X doesn't mean that it isn't effecting your aim just as much, you are simply not aware that it is doing so. You don't see the effect of the mirage in the 6X scope so you attribute the enlarged group to some actual physical updraught that the mirage has on the bullet, yet that updraught can't be detected as an upwards tail twitch or leaves lifting off the ground or something of that nature. If it moves the bullet it must also move the flag tail.

Bryce
 
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Pete

At the time I was involved in using a Rail Gun in mirage analysis we were trying to asses the ability to use a spotting scope, digital imaging and image analysis software to be able to determine (“see”) the target image at longer ranges (300 and 600 yards) in spite of mirage and other atmospheric effects.

The test protocol required using the Rail Gun and sighting it and the spotting scope in at target center just before dawn to be free of pollution, wind and mirage and leaving them so sighted during changing conditions through the day. The five shots groups were fired at a rate of one shot per minute. Additional groups were shot whenever a notable change in conditions occurred.

Since your 5:06 2/3/08 post I asked my test associate to find and recheck the test targets both setup and with strong “boil” but no wind. He reports the following:

300 yards – setup: 5:40am 52deg 43%rh; group size 0.242in circular on center – boil: 4:20pm 82deg 61%rh; group size 0.245in circular centered 0.322in up and 0.012in right of center.

600 yards – setup: 6:10am 54deg 44%rh; group size 0.450in circular on center – boil: 3:50pm 78deg 60%rh; group size 0.315in wide and 0.885in high centered 0.902in up and 0.133in right of center. Note: done 2 days after the 300 yard tests.

Our conclusion is that at 300 yards, the thermal turbulence seen as “boil” did coincide with a shift in point of impact of the group center but no change in group size or shape while at 600 yards there was a proportional shift in point of impact of the group center and a change in group shape to a vertical oval (more vertical dispersion).
 
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