f class shooters question, boil mirage
- Thread starter kawsam62s
- Start date
Ran into this a few times coaching, I take the shooter to 6 o’clock on the known hold. Expect a high shot basically with less if any wind effect.
You will encounter situations where the dominant wind condition is a true headwind or tailwind and you will be forced to shoot the boil. In those situations careful study, either during the previous relay as a scorer or during the initial minutes of the match as a shooter, should reveal that your predominant condition will appear as a boil in the scope. I try to find a couple of flags that seem to be very reliable for direction and try to find which side of the pole the flag is favoring (usually the flag tip/body may just be barely on one side consistently and it can require close evaluation to notice that little hint some days). Usually that flag(s) will be a bit downrange. I run my sighters during that flag position/mirage condition and try only to shoot the same during score. If a cloud comes overhead and darkens the target I hold fire or will hold a half ring/ring low or opposite if my favorable condition is more overcast and I am forced to shoot a bright condition if time is running out. For a new shooter the mantra of 'don't shoot in a boil' is good advice but as you get further along you find this is only relative to the sum of all events that are happening during the relay.
Robin
Robin
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Ned Ludd
Silver $$ Contributor
I have heard "Never shoot in a boil" for as long as I can remember. As an F-TR shooter, in fact I will shoot in a boil every possible chance I get, and I've shot plenty of cleans with high X-counts under predominantly boiling mirage conditions. I hope for a boil. I pray for a boil. I absolutely love to shoot in a boil and have never found any major changes in POA were necessary to keep my shots in the X-ring/10-ring.
My understanding of the old prohibition against shooting in a boil is largely due to the concept of diffraction. As described in Snell's Law, light passing through two mediums of different density will have a different angle of incidence in each medium that is proportional to the density of each. An example of this is how a straw placed in a glass of water looks. Viewed from different directions, the regions of the straw above and below the liquid appear to be bent, or even separated, relative to one another.
Yet we know in reality that the straw is a single straight piece of plastic. Likewise in target shooting, the idea is that the differing densities of warmer and cooler air currents (i.e. "mirage", of which a "boil" is one type) can cause the target center to appear to be in one location through the scope, but in reality you're not aiming at the spot on the target face you think you're aiming at due to diffraction of the image.
While this phenomena clearly occurs, I do not have a good explanation for why I seem to shoot so well in a boil, when so many shooters over the years tell you specifically not to do that. My guess is that the actual displacement of the image when viewed through the rifle scope during a boil is not sufficient to move my true POA outside the X- and/or 10-ring. In that event, the effect of the boil condition for me is simply to take most, if not all, horizontal wind deflection out of the equation. In other words, for me it's more like shooting in a dead calm. I can imagine that my scope magnification (I rarely ever run the mag above 32X or so), and the specific conditions at the ranges I shoot most often may also be contributing factors. In other words, a "boil" condition at one range may actually be much worse than another, even though they might look the same to the shooter.
The bottom line is that you should actually practice shooting in a boil. The reason for this is to build some understanding of what it looks like and how it will affect your shot placement on the target. If you really don't like shooting in a boil, you can usually simply choose not to. However, if you have a some understanding how it can affect your shots, you will be in a position to shoot in a boil if/when it becomes necessary and maintain a good score. It's just another tool in the kit.
My understanding of the old prohibition against shooting in a boil is largely due to the concept of diffraction. As described in Snell's Law, light passing through two mediums of different density will have a different angle of incidence in each medium that is proportional to the density of each. An example of this is how a straw placed in a glass of water looks. Viewed from different directions, the regions of the straw above and below the liquid appear to be bent, or even separated, relative to one another.
Yet we know in reality that the straw is a single straight piece of plastic. Likewise in target shooting, the idea is that the differing densities of warmer and cooler air currents (i.e. "mirage", of which a "boil" is one type) can cause the target center to appear to be in one location through the scope, but in reality you're not aiming at the spot on the target face you think you're aiming at due to diffraction of the image.
While this phenomena clearly occurs, I do not have a good explanation for why I seem to shoot so well in a boil, when so many shooters over the years tell you specifically not to do that. My guess is that the actual displacement of the image when viewed through the rifle scope during a boil is not sufficient to move my true POA outside the X- and/or 10-ring. In that event, the effect of the boil condition for me is simply to take most, if not all, horizontal wind deflection out of the equation. In other words, for me it's more like shooting in a dead calm. I can imagine that my scope magnification (I rarely ever run the mag above 32X or so), and the specific conditions at the ranges I shoot most often may also be contributing factors. In other words, a "boil" condition at one range may actually be much worse than another, even though they might look the same to the shooter.
The bottom line is that you should actually practice shooting in a boil. The reason for this is to build some understanding of what it looks like and how it will affect your shot placement on the target. If you really don't like shooting in a boil, you can usually simply choose not to. However, if you have a some understanding how it can affect your shots, you will be in a position to shoot in a boil if/when it becomes necessary and maintain a good score. It's just another tool in the kit.
Evening
As others have stated shoot low 10 ring. (not in the 9). A boil gives the illusion the target is higher then it appears. If there is heavy left to right mirage then a boil will have less elevated displacement and you could hedge and aim low X ring. OR wait and see if the guy beside you shoots in the condition and adjust. If he hit centre aim low, if high adjust equally amt , if his shot is low is it a 10, or a dreaded 9 and hedge accordingly
http://bulletin.accurateshooter.com/2017/02/mirage-is-your-friend-great-article-on-reading-mirage/
Accurateshooter runs this mirage article every now and then
Trevor
As others have stated shoot low 10 ring. (not in the 9). A boil gives the illusion the target is higher then it appears. If there is heavy left to right mirage then a boil will have less elevated displacement and you could hedge and aim low X ring. OR wait and see if the guy beside you shoots in the condition and adjust. If he hit centre aim low, if high adjust equally amt , if his shot is low is it a 10, or a dreaded 9 and hedge accordingly
http://bulletin.accurateshooter.com/2017/02/mirage-is-your-friend-great-article-on-reading-mirage/
Accurateshooter runs this mirage article every now and then
Trevor
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XTR
F-TR obssessed shooting junkie
My thoughts for what they are worth and remember you read it on the internet.
I agree that a boil changes the location of the target image, but what I have found is that when the mirage disappears at 1000 yards shots go almost ½ MOA high. I'm not going to try to explain it, but I've seen it too many times with rifles that shoot tight. I've seen it really noticeable at Connaught, and at Laurel in MS. I picked up on it at Connaught, I noticed it 4 shots too late and it cost me a match at Laurel. (Craig Martin picked it up sooner than I did that day) Both ranges can and do go from soup to clear due to passing cloud cover. It's the opposite of conventional wisdom. (though it fits with the "lights up, sights up" mantra from sling shooting)
Shooting in a boil, if you don't you're likely going to have a harder time at Raton, because it's the easiest 30 seconds you're going to have in a relay. (note you can get a boil when the wind is blowing from 12 or 6 o'clock)
Many of the things we in F class learn about shooting at long range comes from sling shooters, they have been doing it longer, and some of those things may apply less to the way F class shooters shoot. In this case think that the time delay from making the read until you shoot has something to do with the "rule". Some sling shooters are fast, but even the fastest are probably not as fast as an average F class shooter getting from a spotting scope to breaking the shot, and definitely not as fast as a guy who uses his rifle scope to read wind. With that thought, when you see a boil it often means that there is a changing condition, as an F class shooter you can send one in what you see, but a sling shooter has to come out of the scope, and he doesn't know what's happening as he gets the rifle steady and breaks the shot so he can't see what he's shooting in. So there is a fair chance that if a sling shooter starts to shoot in a boil, by the time he breaks the shot it may not be boiling (going back to the idea that the boil marks a changing condition. When you think about it from that perspective it makes sense.
I agree that a boil changes the location of the target image, but what I have found is that when the mirage disappears at 1000 yards shots go almost ½ MOA high. I'm not going to try to explain it, but I've seen it too many times with rifles that shoot tight. I've seen it really noticeable at Connaught, and at Laurel in MS. I picked up on it at Connaught, I noticed it 4 shots too late and it cost me a match at Laurel. (Craig Martin picked it up sooner than I did that day) Both ranges can and do go from soup to clear due to passing cloud cover. It's the opposite of conventional wisdom. (though it fits with the "lights up, sights up" mantra from sling shooting)
Shooting in a boil, if you don't you're likely going to have a harder time at Raton, because it's the easiest 30 seconds you're going to have in a relay. (note you can get a boil when the wind is blowing from 12 or 6 o'clock)
Many of the things we in F class learn about shooting at long range comes from sling shooters, they have been doing it longer, and some of those things may apply less to the way F class shooters shoot. In this case think that the time delay from making the read until you shoot has something to do with the "rule". Some sling shooters are fast, but even the fastest are probably not as fast as an average F class shooter getting from a spotting scope to breaking the shot, and definitely not as fast as a guy who uses his rifle scope to read wind. With that thought, when you see a boil it often means that there is a changing condition, as an F class shooter you can send one in what you see, but a sling shooter has to come out of the scope, and he doesn't know what's happening as he gets the rifle steady and breaks the shot so he can't see what he's shooting in. So there is a fair chance that if a sling shooter starts to shoot in a boil, by the time he breaks the shot it may not be boiling (going back to the idea that the boil marks a changing condition. When you think about it from that perspective it makes sense.
It doesn't or at least not to my understanding
for discussion i take a light breeze to be 4-7mph
Some additional contributing factors responsible for elevation, wind direction, wind strength and rifle twist.
If you look at the wind vector chart you note a left to right wind pushes down while a right to left raises. In the absence of wind (a boil) the effect on the bullet is gone.
example: wind coming from the left requires 1/2min more of elevation. as seen in the diagram for 10-11-12 when the wind changes to a boil; compensating by aiming low reduces the chance of an elevated shot as you have taken off the extra elev previously added.
Right wind 1-2 the shot is reasonably centered or slightly high. Aiming low for right wind protects the 10 ring in a boil. if you estimated correctly the shot will come up a mid 10 where you aimed or an X or 10 if there was residual left wind.
light wind 1-3mph has less effect
Trevor
memilanuk
Gold $$ Contributor
Early on in my F-class journey, I encountered a situation where the effect of a boil was made painfully obvious.
I was shooting a 3x600 match in western Washington in July. First string in the morning, my come-ups from my home range (on the other side of the mountains, aka the 'dry' side of the state) were fairly close - within a click or two. The second string wasn't much different. But, given the way the relay rotation worked out, I ended up shooting one of the last strings of the day, around 1400 or so. Nice n toasty.
To add to the fun, this particular range is set up so the 600yd line overshoots a lower 200yd firing line... that has an asphalt shingled cover over it. *Lots* of mirage off that thing.
I'd found that in order to put my shots in the X-ring, I was having to hold at about 7-7:30, just into the 9-ring. Weird, but thats what worked. Then, about half-ways through the string, a slight breeze happened to come through for just a minute or two. As luck would have it, I was on the gun, taking up the trigger to break the shot with the flags go from dead limp and the heavy mirage maybe leaning to 1 o'clock... and suddenly that breeze just 'wiped' the boil away.
Like I said, my hold was down @ 7 o'clock into the 9-ring. Imagine my surprise, as the X suddenly 'jumped' down to almost exactly where I was holding! I was more surprised and curious than anything, so I sat there just watching. The breeze blew through, and died. The flags went limp again (they'd only really lifted the tails and turned on the poles to begin with)... and as I watched, the X slowly started climbing up again as the mirage/boil came back. Soon enough, I was 'aiming' at the same point I started at, 7 o'clock just into the 9-ring.
I *really* wanted to see where this one was going to go... so I sent the round down range... and it came up an X
I'm not a physicist... but the various situations I've seen over the last decade or so of shooting F-class at different ranges around the country (and beyond) seem to bear out the basic premise that the mirage will displace the target image up and/or to the side to some degree, depending on the range conditions.
BoydAllen
Gold $$ Contributor
I have a suggestion. If you know a short range benchrest shooter who owns a rail gun, ask him to bring it to your thousand yard range, assuming you have benches that are very sturdy, so that you can set it up on target and observe the correlation between various mirage conditions and where the cross hairs line up on the target. Lacking that resource, you could devise a scope mount that would be sufficiently immobile to do the same thing. There is no need to guess.
Assume a full value wind. If a boil is simply the period of mirage not running laterally, the likely reason the shots go higher is because they aren’t being thrown laterally into the wind to be blown back into the X. That makes for less distance travelled.
Less distance travelled makes for a shorter flight time. Shorter flight time makes for higher impact. Agree with Jerry as to how lateral wind could change apparent height of target.
Edit: Looks like a .308 at a 1,000 yards is dropping very, very roughly about a foot every 10 yards, so to get say a 3 inch drop on target you would need on the order of magnitude of 2-3 further yards travelled. 1-1/2 yards added while going away from the target and the same added being blown back in. That does seem to require way more wind to create the drop than we see, though.
Less distance travelled makes for a shorter flight time. Shorter flight time makes for higher impact. Agree with Jerry as to how lateral wind could change apparent height of target.
Edit: Looks like a .308 at a 1,000 yards is dropping very, very roughly about a foot every 10 yards, so to get say a 3 inch drop on target you would need on the order of magnitude of 2-3 further yards travelled. 1-1/2 yards added while going away from the target and the same added being blown back in. That does seem to require way more wind to create the drop than we see, though.
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I was discussing this yesterday with my shooting buddy. We were wondering if perhaps displacement is the result of repetitive/additive refractions in a boil. And perhaps when wind churned the air, the additive function did not occur.
dannyjbiggs
Silver $$ Contributor
XTR is right-on in his comment. I shot service rifle many years, mainly on USAR rifle teams back in the 1980's using the M14/M1A, and we used the spotting scope to access what mirage was doing. The rule pounded into us by our coaches was "never shoot in a boil"...specifically because conditions could change while one was getting off the spotting scope and shouldering the rifle to make the shot. So that is the carry over rule that shooters often repeat. Later on, as a Palma shooter, I learned to keep my rifle shouldered and my non-shooting eye on the scope as the other eye was in aiming mode, so I found it a little less risky to shoot in a boil. But, as an F-Class shooter using a rifle scope and reading mirage from it, like others on this post have stated, I relish being presented with a "boil".
Dan Biggs
Ned Ludd
Silver $$ Contributor
XTR is right-on in his comment. I shot service rifle many years, mainly on USAR rifle teams back in the 1980's using the M14/M1A, and we used the spotting scope to access what mirage was doing. The rule pounded into us by our coaches was "never shoot in a boil"...specifically because conditions could change while one was getting off the spotting scope and shouldering the rifle to make the shot. So that is the carry over rule that shooters often repeat. Later on, as a Palma shooter, I learned to keep my rifle shouldered and my non-shooting eye on the scope as the other eye was in aiming mode, so I found it a little less risky to shoot in a boil. But, as an F-Class shooter using a rifle scope and reading mirage from it, like others on this post have stated, I relish being presented with a "boil".
Dan Biggs
Like you, I also relish being presented with a boil, as I noted previously. Nor am I at all opposed to being presented something boiled (or roasted) with relish on it. Either way, boiling can be your friend.
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I have learned that i need to aim at lower image of target in mirage. I dont know the term, but sometimes, the target seems to be flickering, going high and low, consistently. I aim at the lowest point of the movement of target (for my POA ), and have usually found to maintain decent vertical by doing so.
dcali
Bullet Maker
I think the biggest problem with a boil is not the diffraction that moves the target image, but the fact that you’re more likely seeing a head or tail wind than no wind.
A head or tale wind makes your wind calls extremely sensitive to small changes in wind direction. Throw in the difficulties of a shifting target, and it’s quite challenging. Don’t fall for the trap that a boil means you can ignore the wind. As long as you keep track of how quickly it’s shifting, you can shoot a boil. But it’s like any other head or tail wind. The mirage just plays with your head a little and puts you in the mindset that there’s no wind.
A head or tale wind makes your wind calls extremely sensitive to small changes in wind direction. Throw in the difficulties of a shifting target, and it’s quite challenging. Don’t fall for the trap that a boil means you can ignore the wind. As long as you keep track of how quickly it’s shifting, you can shoot a boil. But it’s like any other head or tail wind. The mirage just plays with your head a little and puts you in the mindset that there’s no wind.
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