OzFclass

Ok , since we have some very highly esteemed
Shooters on this site . I'm going to throw the cat among the pidgins and ask the question .
Is near flags/wind or far wind/flags more important ?
Graham Sells .

It probably wont be one or the other as its all relative to the conditions.

Well for me , I would have to agree . To qualify this I'm only a newbie . I think north arm is a classic for this . The locals say the wind sock close to the butts is the key. At Dalby because of the flat open land , near maybe more important .
But as a general rule of thumb . Is there any other thoughts ?

Graham,

It depends very much on the topography of the range, location of shelter trees, wind direction etc. But even for the simple situation of cross-wind on a flat range, it depends on who you listen to . James Owens in his book "READING THE WIND" says the closer flags are more important, whilst David Tubb looks at central or further flags!

Mr Owens theory is that because closer winds deflect the bullet sooner in its flight, then the overall effect will be greater. I haven't heard Mr Tubb's explanation.

Personally I subscribe to the Owens explanation, although with fluid dynamics, things are not always as they seem!

Alan

The wind sock at North Arm is a key indicator in a condition where a 3:00 wind comes over the hill, rams through wind tunnel that is the SSAA carpark and streams across the range between the 300 yard line and the butts. That wind can't be felt at any mounds and there are no flags or trees directly in the causeway to identify it, hence why its an important indicator. It just happens to be a common condition at that range I suspect due to the landscape and being close to the coast.

There are other keys for other conditions that also happen regularly, but we don't like to tell non-locals about those ones.

I think all ranges have common characteristics in certain conditions and thats why local knowledge is so accurate. I guess the trick is to be able to read the landscape and understand the wind flow from any given direction in unfamilliar locations.
I watched a doco on snipers a while ago and they would draw a mudmap of the field in front of them, including hills, trees, terrain, etc. They would study the mudmap and imagine the wind rushing through the fields as water would.

Although near wind combined with a reducing MV causes parabolic bullet deviation from the get go, I've been caught badly by near winds and by far winds so I think they're both equally important, just have to identify which is causing the most havoc on the day.

Further to what I said above, there's a couple of things which work in favour of Tubbs theory. (1) The projectile is going slower the further it is from the muzzle, so will be affected more by the wind, and (2) The projectile will be at its highest point above the line of sight at a distance past halfway to the target. Generally wind speed increases with height above the ground.

So, these factors on their own (and there will be others) could potentially cancel out the effect subscribed to by Owens.

There are other keys for other conditions that also happen regularly, but we don't like to tell non-locals about those ones. D A

Hi Dennis , what u don't want tell the whole world the secrets of North Arm ???lol.
North Arm depending which way the wind is coming from is for the most hardest range that I've shot on . After coming last in 2012 and almost quit the sport ( that's how demoralised I was !). In 2013 set out to do what u said Dennis . I must have spent nearly a couple of hours the day before at the range imagining the wind as water and how it flowed . This little exercise netted me a win on the Sat .
But on the Sunday .....the 600 yd line is something to behold !! All of the flags were pointing at each other . I didn't have a clue ! Managed to salvage 3 rd for both days .
I love north arm ! It's a challenging place .
Also Dennis , congrats on ur win at Wandai! I had a bad second day ! My plan was to continue the possibles but was humbled ! Win is a win though.
Cam mac was unbelievable in getting a couple of possibles in crap conditions . He is my hero! And Julie of coarse ! Lol.
My biggest problem is I got worked up and couldn't sleep and my memory and mind was fatigued . It was readable but u had to be sharp which I wasn't !

Thanks all for the replies I agree with it all . Range time is the only way to tell what's important and what's not ! Regards Graham.

Thanks Graham, we all had a bad second day (except Cam and Julie). I was third down. dropped points and came off the mound thinking I'd be lucky to take 5th. ColS, PhillD and I all stayed very close and a 1 point win is pure luck. I was very surprised at the end of the day.

Wondai was an interesting lesson for me. DaveH's comment was "The flags here are for decoration". I laughed, shrugged it off and quickly learnt that he was telling the truth.
The dust cloud from bullet impact at the back stop would drift left and then when it reached the height of the target, it would get blown off to the right.

It's an uphill range with a heavy tree line running its length on both sides. I wonder if that keeps the flight path of the bullet just below the flags at the shorter ranges which may explain why mirage is so important there. I feel the flags were more truthful at 600 and that may be the point that the flight path was more exposed above the flags. Just guessing.

It was a nice photo of u three too !
Mirage was important there . At 700 that flag in the gully held some weight too along with the mirage .
What's ur thoughts Denis ?

Which photo was that Graham? Never got to see one.

Yep, I reckon 600 yards and further is where the flags were being more truthful.
From memory the 700 yard mound is inline with small bore range on the right which is where the tree line curls and allows the wind to curl with trees and run across the fullbore range.

Mate ur famous lol . Lookup wandai results Qra website !

With that flag ... It was in a gully about the 600 or 500 yd line . I just figured it out toward the end . I think flags in gullies nearly always rule !

That's a terrible photo, no one told me I was balding!!!!

DenisA wrote:That's a terrible photo, no one told me I was balding!!!!

What it's happening to u too! My family is giving me a hard time about that , especially when it comes to my wife cutting my hair or lack off it . Lol
Anyway ... Way off track !

Reading the wind.

Ceterus parabus has never been truer when learning to read the wind. By this I mean, learn the basics first and assume all other variables are constant. Step by step add another variable to your analysis to build on your repertoire of skills. Reading the wind calls for keen observation skills, the ability to interpret those observations, to use mental arithmetic, understand percentages and make a prediction about conditions as you execute the shot. These, high order, thinking skills are in addition to hand eye co-ordination, fine motor skills, reflex and increase your probability of a higher score given the luck of the draw.

The Basics
Ceterus Parabus: that we are shooting on a flat open range without obstructions to alter the flow and density of the air mass and where micro climates are absent. We are shooting at sea level at the standard temperature and air density used for calculations. We also need to hold constant light intensity and direction, Magnus and Coriolis effects; and ballistic coefficients of bullets. We also have to assume a given and constant muzzle velocity. That the flags used are the standard weight and length as prescribed by the rules and they are not wet. For purposes of discussion we assume all wind quarters are equal in wind allowances. I will refer to the sector 12 o’clock to 3 o’clock.

If you are to learn patterns through experience, the most important factor is to have your rifle zeroed for windage. For approximation I still use a zero target at 21.83m or 71ft 7 in at which distance a minute of angle subtends to 6mm or ¼”. As a tip, I used to re-fire on the same zero target in the same position after a competition to establish over time, elevation zero’s for each distance which I mark on the old zero target. I then scanned the old zero target and printed it off for future reference and re-used it as a zero target. Do this for each rifle and maybe different venues. Of course, go a bit further and keep notes for advanced applications e.g. air density.

I liked to use the Beaufort wind scale as a measure of wind force. It was developed for sailors and to me indicated the wind forces best, from an observational perspective. The standard range flagging we use today was originally used by fullbore competition in terms of cloth weight and shape to accommodate the Beaufort scale. I think of it as graduations - as Force 1, Force 2, Force 3 etc. rather than the actual graduations in 4 miles per hour. This does not confuse people with a metric, gut measurement of value when explaining it to people much younger than me. I also apply this basic wind force to mirage calculations. So flags and mirage are my key wind indicators.

Mirage is more important than flags in calmer conditions because it has no inertia to overcome. Therefore there is no delay as with flags. In an instant you can assess wind up to Force 3 (12 m.p.h), at which point it flattens out and becomes unreadable.

Reading mirage is less complicated than reading the flags and therefore less taxing on the brain. It only requires the shooter to associate a scope mirage pattern with a wind force equivalent to a 3 o’clock allowance at each distance. Whereas, a flag reader has to determine the height of the flag tail with associated wind speeds, then look at the angle of the flag to establish wind direction then combine calculations of speed and direction at each distance. Manual wind calculators are permissible so getting on the target with sighters should not be a problem if using the flag method. If possible shoot your sighters at the extremes of conditions and shoot for score in the window you have evaluated assuming your rifle zero is correct.

Using Mirage – Basic.
You must commit to memory the wind allowance for the Force 1 wind at 3 o’clock, at each distance and use it as a base wind for mirage calculation.
Scenario.

Assume we are at 600 yards and the allowance for a Force 1 wind, is 2 minutes of angle at 3 o’clock. Looking through our scope we see small and feint mirage ripples zipping right to left. It’s Force 3 - crank on 6 right from zero i.e. 2 (Force 1 base wind allowance) x 3 (Force 3) = 6 minutes right.

Next, the wind changes, the scope reveals a clear flowing mirage from right to left. It’s Force 2. The difference between Force 2 and Force 3 is Force 1, come off 2 points. Or recalculate from zero, i.e. 2 (Force 1 base wind) x 2 (Force 2) = 4 minutes right.

If the mirage just decides to drift in an angular fashion just crank on the base wind allowance which is Force 1.

Sometimes we get those days when it’s not quite a boil (no wind correction) but a tendency to drift with steeper angles in the mirage pattern. This is equivalent to a ½ base wind (2 m.p.h.). So at 600 yards it would be equal to 1 minute wind allowance.

Advanced shooters would combine calculations with Magnus force drift at 600 and the apparent aiming mark shifts that oscillate in a vee fashion if wind fishtails. Sometimes it’s like dancing with the wind, three steps forward for the major force, one step back for the counter factor, 1/2 step forward from a push behind.

Mirage and Flags

Mirage is useful to determine the direction of the wind if you care to combine flag use. A useful strategy before sighters is to point your scope in the direction of the boiling mirage to indicate wind direction. If you can observe and time the direction extremes you can establish a window in which to shoot. If you have sufficient time before you shoot you can determine the prevailing direction.

Occasionally we witness flags going in all directions and mirage is very choppy. Perhaps I need some help from Barry Southern, but what I think is happening in a lot of cases is that the range is heated more rapidly from the mound to the butts and cold air is drawn in from the sides which are often shaded or have taller grass, vegetation etc. which holds cooler moister air. This air in Australia rises in a clockwise spiral. The prevailing wind blows these local willy willies often unseen by the naked eye (can be more than one on a wide range) slowing and changing their direction as they meet obstructions or uneven terrain. Elevation becomes a bigger problem because: i) the apparent aiming mark shifts; ii) high shots due to clockwise wind spiral; and iii) complete reversals if cooler air converges due to cloud cover. Various shooters along the mound can experience a different condition at the same time. Shooters to the right of the willy willy centre will lose shots higher left, and conversely shooters on the left will lose shots marginally high right. This is exacerbated or countered by the magnus force effect at long range. In lighter winds the apparent aiming mark shift is greater than the magnus force effect and sometimes they can combine at long range (e.g. a right wind raises combined with a drifting higher and left apparent aiming mark which may be caused by light intensity and direction. A famous American rifleman by the name of Anderson used to grade mirage distortion into three levels). If the prevailing wind emerges then shooters on the edges will be subject to turbulence if there is tree cover on the sides. I prefer a breeze any day and feel it’s easier to judge the pushups on flags than the drop offs due to inertia that has to hold them up. Aiming mark distortions disappear too.

The wind can have different zones and characteristics in a general sense. This explains why people look at different flags and might comment that the butt flag, for example is the one to watch. But a bullet once deflected cannot recover that initial deflection angle unless there is another countering wind zone. We know modern ballistic programs account for decaying projectile BC to enable us to calculate, wind drift, spin drift, etc. so we can come up with a deflection figure that’s on the money. What we can not readily identify is what air flow disturbance is changing the anticipated result. We know air runs faster in gullies, so flags near those will be punching above their weight. If we had flags set at heights which matched the trajectory of the bullet we would soon see which had the most influence.

I think what explains Tubb’s reasoning is that the atmosphere is in layers and that wind at the highest part of the bullet trajectory will have more effect because it is running faster than ground level. Of course the range slope may enhance or exacerbate this factor.

You can use a ballistic program to plot the trajectory to identify what distance is the highest point at which you could associate a flag with. In the past I often tuned my rifle just before this point.

The old rule was that the first 1/3 of the range was worth 60% of the allowance and the balance is worth 40%. It’s a good rule for intermediate level shooters and not far off Alan’s interpretation of Tubb in that attention is paid to flags at the end of the first third of the range. But the closest flag set the agenda unless a flag down range is more powerful.

I personally looked at the trend of all of the flags, assessed structures or terrain for a dominant flag, picked a flag for trajectory high point and tried to align mirage with flags and shoot in a window where possible. Most importantly, in conditions with no mirage I concentrated on flags to the windward side of my bullets path. On big ranges I cast an eye on flags to the far windward position in rough conditions to see what’s coming in order to time my shots as the wind arrived.

As far as calculations go with flag reading I committed to memory the Force 1 base wind allowance for each major angle and merely multiplied the base wind allowance by the prevailing wind force factor. This is different to that of mirage calculation which only uses the 3 o’clock angle. In calculating the windage for a 1 o’clock direction at Force 4 (16 m.p.h), I multiplied the 1 o’clock base wind of 1 minute by 4 (Force 4) = 4 minutes.

These base winds for each direction can also be calculated. A 1 o’clock wind is exactly half the 3 o’clock allowance, and a 12.30 o’clock wind is ¼ of the 3 o’clock allowance. These directions are the most important to learn in dealing with fishtail winds because the windage changes are huge and to beginners seem counter intuitive. On the other hand, the wind calculation for 2 o’clock is merely 7/8 of 3 o’clock and a 1.30 o’clock wind is 7/10 of 3 o’clock. As a general rule direction changes are more important to pick up in a fishtail and strength changes are more important to observe in full value winds from 2 -3- 4 o’clock.

In flogging winds, the ripples in the flags or pulse should be observed as poles can bend over and the tail height becomes meaningless unless you can read the pole bend assuming they would spring back. I used to align a tip of a flag with another object as a reference point if I could, such as a post , a drum, a number, tree, a hut and used these to indicate strength and direction.

Unless you are reading mirage, keep your head out of the scope, and on the flags as soon as you fire because it’s more about reading the wind than firing the shot in the long run.

Finally, there is no substitute for practice. A few years ago, NRA High Power Competition Shooting computer game was produced for this purpose. But I feel an Australian simulation produced by Mr Smith (I think) from Queensland was really great and put on this site, gave particular emphasis to different flags. It would be great if Alan could contact him to put it back as a download so all could benefit.