Boil?

[rfair]

Ok, I've read the article about the guy named Froggy several time on this site and I've always come back to the same question when he is talking about shooting in the wind. He says to never shoot in a boil!
Now I've shot and reloaded about 30 years and in the last 10 years, I've been trying to push my self to shoot better and learn all I can! I can see mirage blowing either way but I don't know what a boil looks like. so what does it look like?
Please be nice!

 

[BoydAllen]

In an absolute dead calm the mirage goes straight up resembling boiling water. The difference in refractive index of the air in this condition causes the image of the target to be displaced upward, and if you aim at the displaced image, your shot will be high by the amount of the displacement. The kicker is that many scopes are not of high enough magnification for the shooter to be able to see a boil. In any case, if you take a shot in what appears to be a momentary dead calm, and it goes high, you may have been aiming high and not have known it.

 

[queen_stick]

I too have only recently been paying attention to the details, especially with watching the wind. I have a long way to go...

A few weeks ago I was shooting my new 6BR for the first time. It has a NF 8-32 on top, and this session was also the first time I was using that scope. At 100yds, I had the thing cranked to 32x, and could see the target very clearly, with slight mirage running left to right. At one point, for about a second or two, I couldn't even see the target - just a nasty blur in the cope... the wind had completely stopped. I've only seen this a few times, but I don't shoot as often as I should either

I'm pretty sure that's a boil, and I clearly understand why you wouldn't want to shoot in that condition. That's also caused by REALLY bad mirage. I think most of what you will see is as described above, by Boyd.

 

[rfair]

Thank you Boydallen! I'm going to start watching for that!!

 

[1000yardstare]

I have two totally different approaches to boil.

On a narrow civilian short range (300 yds) with high side berms I shoot only on the boil because it is truer. Wind coming from an angle tends to swirl in this physical setup and is difficult to read. The boil going straight up is easier to read. Sights are adjusted accordingly.

On a wide open Army long range (1000 yds) I sight on the prevalent cross flowing mirage and only shoot on that cross flow, never on a boil. The boil is treated as a danger sign that the wind is about to change direction and care is exercised accordingly.

 

[rfair]

1000ydstare,
So your saying, that when the wind is changing, it may or will go into a boil? I'll have to just go out and watch on my range to see what I can see happen!
Also a good note about the certain setup of ranges could affect wind differently. All very interesting!

 

[1000yardstare]

rfair, on a wide open long space such as an Army range where the wind is natural in its changes, a boil is usually the sign of a switch in wind direction from the prevailing condition to the abnormal condition. And there will be a boil back to the prevailing condition.

Fullbore shooters are constantly watching the wind flags before going to the line. During the 5 minute prep TR and F Class shooters are looking for the prevailing mirage drift through spotting scopes or scope sights. After prep the two sighting shots are shot only on the prevailing drift. Once the mental computer has adjusted for slight variables, all scoring shots are only shot on the prevailing mirage drift.

On narrow civilian short ranges with high side berms and close forests, at least in my experience, there is too much wind swirl to find a prevailing mirage drift. So out of self defence, I personally only shoot on a boil because it is the one constant that is predictable. I have never seen a boil on a short range that is so fierce that you cannot make out the target. Fire a few sighters, adjust your scope and have some fun.

All of the above does not apply to the British Isles where only a Druid sorcerer can make any sense out of the wind. Sorry Laurie.

 

[rfair]

Thank you for your input!!

 

[watercam]

A "boil" also show up when wind is at 12 or 6 o'clock. On the 1000 yd. range we shoot (at Camp Pendlton, CA) the range is set up facing the ocean. Consequently we have wind in our faces most of the time compounded by the canyon it flows through which winds back and forth. On top of that there are berms every 100 yds. so that wind bounces off and up over these berms. Not so bad at mid range where the top of the bullets trajectory lies but at each end it can have a mother of effect. Many's the 8 or 7 ring at 11 to 1 o'clock or 5 to 7 o'clock I've scored missing wind changes in my face.
Please, give me a cross wind every time!

 

[Steve Blair]

Watercam is certainly correct about Pendelton. The same is true at Dulzura when the wind is southerly, blowing on our backs. Add 100°+ summer temps and mirage can look like you are shooting from the deep end of the pool. I have seen a 12" diameter bull completely disappear at 300 yards for several seconds. It is difficult to shoot what you cannot see.

 

[Rustystud]

Reading the wind is and learned ability. A few years back I went to the Long Range Shooting Clinic put on by Mid & Nancy Tompkins, and Kent Reeve all of whom are masters of reading the wind. I learned more in three days about reading the wind than 40 plus years of shooting.
Nancy's book on long range shooting is a great read on this subject.
I squaded beside John Whidden at the F-Class Nationals last year. He used both his scope and a spotting scope. I inquired as what he was doing. He of course had his scope focused on the target he had his spotting scope focused at the 900 yard line. He was more interested at the mirage and wind at 100 yards than at 1000 yards. John explained to me he was more interested in the wind effects on the bullet on the front end of the bullets flight.

This might add some more thoughts on the subject.

Nat Lambeth

 

[1000yardstare]

Two years ago at the 2008 Ontario Fullbore Champs we ran into a condition during the Saturday 900 yard match in the afternoon where very few boils were seen. The mirage was running right to left at 400 yds and left to right at 700 yds. It was fairly constant all afternoon. The 6 wind flags were all pointing in different directions. Experienced F Class shooters focused on the 700 yd mirage and high scores were obtained.

I squadded with a cadet shooting TR who was struggling with her shots. I asked her where her spotting scope was focused and she said "on the target so she could see the markers". I told her to focus on the near mirage and since I was scoring for her anyway I would call her shot location as well as the score. She immediately started drilling the 5 ring and V-bull and shook my hand when we were finished. One happy cadet.

 

[BoydAllen]

Depending on range topography, there can be various conditions that produce unexpected vertical shot displacement due to ground profile induced vertical wind component. A Boil is a specific situation that happens in a calm, when there is no wind, when the target image is displaced upward, and shots go high because that is where they were aimed. Again IMO, not all vertical producing conditions fall under this term.

 

[rfair]

After listening to all of you, I can remember seeing boils at different ranges! I thought it was my eyes playing tricks on me.
Shooting rifles are so much fun and so rewarding, once you reach certain levels of knowledge and skill it just challenges you to the next level and it's sites like this one that help us all to succeed! Thank you!!

 

[BoydAllen]

Except for Benchrest shooters, barrel mirage shields are uncommon. If you see mirage that is that is a generalized deggradation of the scope image, cover the barrel with anything from muzzle to under the front scope bell and then look again. If it looks better, you have a barrel mirage issue. Home made barrel mirage shields cost almost nothing, as do the ones that you buy. I always smile to myself when I see a shooter with a high magnification scope, shooting under conditions where I know that I need a shield. If he complains about his scope image, and I show him how to fix it, then he is confronted with the prospect of having to do something different than what he is familiar with. More often than not, the problem stays unfixed. Oh Well.....

 

[rfair]

Yes, I've had the heat from the barrel mess with me as well but my style of shooting is more tactical than benchrest and I hate to put a heat shield on but may have to resort to it! I suppose those 2 pcs of velcro wouldn't look that bad.