Quantifying wind reading ability

[Bryan Litz Ballistics]

I don't want to detract from the current interesting thread about wind flags, but I've got a question I feel is different enough to start a new thread.
It started on another forum,long-range.com), and I wanted to broaden the exposure.
I'll copy my post from long-range here for discussion:

When I first read your post, I got the impression that you were trying to find out numbers, like +/- 2 mph that is discernable by various level shooters. There's been a lot of good discussion brought up, but no-one has dared to put numbers to it. Sometimes the best way to get information from people is to just say something arguable. I offer the following scale as my opinion of wind reading ability, and as material for debate.

... Wind ......... Shooter ...... Cross Wind
Conditions ...... Ability ........ Uncertainty
-----------------------------------------------

Calm ............. High ........... +/- 0.5 MPH
Average ......... High ........... +/- 1.0 MPH
Difficult .......... High ........... +/- 1.5 MPH
-----------------------------------------------
Calm ........... Average ........ +/- 1.0 MPH
Average ....... Average ........ +/- 2.0 MPH
Difficult ........ Average ........ +/- 3.0 MPH
-----------------------------------------------
Calm .............. Low ............ +/- 2.0 MPH
Average .......... Low ............ +/- 3.0 MPH
Difficult ........... Low ............ +/- 4.0 MPH

I'll now define what I mean by the various terms.

Wind Conditions.

* Calm is very low wind speeds,0 to 4 mph), from a consisitant direction.
* Average is between 5 and 9 mph, and moderate direction changes, like +/- 30 degrees.
* Difficult is anything over 10 mph, combined with drastic direction changes.

You may put a 12 mph wind that's constant in direction and speed into the 'Average' catagory.

Shooter Ability.
This is the uncertainty with which various shooters can read the various conditions, to 95% confidence.

* Shooters in the 'High' category are like Palma Team coaches.
* Most of us are in the 'Average' catagory.
* Beginners are in the 'Low' catagory.

Cross Wind Uncertainty.
This is exactly what is says. It's a combination of the shooters ability to read wind speed and direction. The uncertainty in cross-wind,as opposed to 'range-wind') is the only important component of wind.,Also not considering the vertical component).

For example, I shot a prone match in Williamsport, PA last weekend. The second match was fired about 1:30 after the wind had picked up to a gentle 3-5 mph. Normally, I'd consider such winds to be in the 'Calm' catagory. However, the winds changed in speed and direction so quickly for me to catagorize it as 'Difficult'. Now, I consider myself to be of 'Average' ability to call wind. According to my chart, this means that 95% of the time, my wind calls should have been within +/- 3.0 mph of the actual cross-wind.

So how can this information be used? Back to the example...
The bullets I shoot drift about 6 inches per mph of cross wind at 1000 yards. So with a +/- 3.0 mph error in wind reading, I can expect my group to be +/- 3mph*6" wide, = +/- 18", or 36" across. That's almost 8 ring to 8 ring. That's about how my group formed up,I actually shot 1 narrow 7 on each side as well).

I've found that taking a portable wind speed indicator out for walks, and trying to guess the wind speed is a good way to improve. It's valuable to learn how certain wind conditions affect a given cartridge/bullet combo, but that information's only good for that combo. If you learn to judge the wind itself, that knowledge can be applied to every cartridge/bullet combo.

The above table is only my opinion about the 'numbers' associated with cross wind uncertainty. I'd appreciate any comments about it. Are my numbers right? Is my table complete?

I think that if we could come up with a standard table, we could more clearly understand the impact of wind reading uncertainty on various cartridge/bullet combo's. It might help some people make more fitting decisions about the equipment they choose.

Thanks,
-Bryan

 

[BoydHeaton]

How fast was the wind blowing at the target...How much of an updraft was there going over the road and the water....How fast was and in what direction was the wind blowing 50 feet over the flags....The wind can not be read at williamsport...Mirage is a different story how ever

 

[BoydHeaton]

And yes I shoot there...And no I don't read the wind

 

[StephenPerry]

Bryan
Nice that you started a separate thread on wind variations. I can only speak for what I have shot out to 600M. I like your your idea of walking the Range with a wind gage. Some shooters write off the wind effects on projectiles. That's why artillery units are the ones that launch the big ones, they have an idea where they might go.
I have always felt that winds closer to the shooter are more important than winds closer to the target. Initial wind contact with the bullet determines what skewed angle the bullets will take. The longer the distances the wider the angle can become. The trajectory angle can change as the bullet goes through wind currents but a well stabilized bullet early in it's course will head for the hanger given the target stays where it was at the start.
I feel this is where the term hummer barrel comes from. LR shooters probably would like to come across a barrel that will stabilize a bullet closer to the shooter giving them more control over their loads. Short Range shooters would die for a barrel that would stabilize bullets within say 30 ft to avoid having to hold over an 1 1/2 in for a 10 mph crosswind at 200 yd. I never get one of those mystery barrels so I do it the old fashioned way, I cheat and read mirage and hope it's there.
Bryan you guys are shooting the big game at Williamsport. I remember being a kid in the 1960's reading reports from your shoots. Seemed 7" groups were the better ones some they didn't publish were probably in the 30" range, some shots never made it to the target. 1000 yd has closed the gap but I'm confidant there are still days when some go home wondering if their bullets are still in orbit.
Nice presentation Bryan most will gain a perspective they never had on wind reading. Some will do things the old fashioned way without any new knowledge. Like crossing the street at night one step behind the Michelin man.

Stephen Perry
Angeles BR