An interesting experiment with wind...

[LRNut]

I posted this on the 10 mph head wind thread but thought it deserved its own:

I just conducted an interesting experiment. I videoed holding my Kestrel up for 39 seconds. I then replayed it frame by frame and recorded the wind speed change every second. The wind was not that fast; it averaged 6.16 mph over that period with a standard deviation of 2.19. I did not track any direction changes; just speed. I then calculated the changes per frame (the Kestrel doesn't update much more than once per second) and found that 18.4% of the time, the wind change within 1 second was 1 mph or greater. One mph is enough to move my group 5" at 910 yards (.338 Edge 300 Berger at 2875 fps). My TOF is 1.1 seconds (you can clearly see the long TOF in my 1047 rock shot; it is 1.5 seconds). So what that is saying is even if I have a PERFECT wind call, over 18.4% of the time it will change during the TOF enough for me to have a 50% chance of missing. Or stated differently, a perfect wind call will result in a miss (outside of 5" from center) 9.2% of the time (takes into account that half my bullets are still going to hit the 10" vital area even if the drift is 5"). But students of calculus would recognize what I really need to do is integrate all the error collectively to come up with a solution. For example, 28.9% of the time, the difference in wind speed was .8 mph or greater. A .8 mph wind will blow my group 5" at 970 yards. So applying the same math, even an absolute PERFECT (yes, I am yelling) wind call is going to result in a 14.45% chance of a miss. And remember, this doesn't consider any directional changes, just speed. It would be really interesting to measure a head wind in terms of change per second in directional shift/speed. Just think what these numbers would look like at twice the speed...

Want to look beyond 1000 yards? It gets really ugly.

I know it is popular on this site to think there is no limit, but at some point, you can't argue with math, unless of course, you are okay with wounding an animal as a trade for bragging rights.

I don't have time to upload the video to YouTube right now but might later.

NOTE: I edited this chart to correct an error: I needed to take the absolute values of the difference when calculating the differences; it made the AVERAGE wind change per second .54 mph.

Seconds	MPH	MPH	Diff	ABS Diff	% > 1 change	18.4%​
1​	4.3​				% >.8 change	28.9%​
2​	4​	4.3​	0.3​	0.3​
3​	4.3​	5.5​	-0.3​	0.3​	Average	6.158974​
4​	5.8​		-1.5​	1.5​	Std Dev	2.192144​
5​	5.8​		0​	0​
6​	5.8​	4.7​	0​	0​	Average change per second	0.536842​
7​	4.7​	4​	1.1​	1.1​
8​	4​	3.2​	0.7​	0.7​
9​	2.9​		1.1​	1.1​
10​	2.8​		0.1​	0.1​
11​	2.8​	2.9​	0​	0​
12​	2.9​	3.1​	-0.1​	0.1​
13​	3.1​	3.4​	-0.2​	0.2​
14​	3.4​	4.8​	-0.3​	0.3​
15​	4.8​	6​	-1.4​	1.4​
16​	6.2​		-1.4​	1.4​
17​	5.5​		0.7​	0.7​
18​	5.5​	4.9​	0​	0​
19​	4.9​	4.6​	0.6​	0.6​
20​	4.6​	4.4​	0.3​	0.3​
21​	4.4​	5.2​	0.2​	0.2​
22​	5.2​	6.4​	-0.8​	0.8​
23​	6.4​	7.6​	-1.2​	1.2​
24​	7.6​	8.5​	-1.2​	1.2​
25​	8.5​	9.3​	-0.9​	0.9​
26​	9.3​	9.8​	-0.8​	0.8​
27​	9.8​	9.6​	-0.5​	0.5​
28​	9.6​	9.7​	0.2​	0.2​
29​	9.7​	8.9​	-0.1​	0.1​
30​	8.9​	8.5​	0.8​	0.8​
31​	8.5​	8.2​	0.4​	0.4​
32​	8.2​	8.7​	0.3​	0.3​
33​	8.7​	8.8​	-0.5​	0.5​
34​	7.9​	8.5​	0.8​	0.8​
35​	8.5​	7.9​	-0.6​	0.6​
36​	7.9​	7.8​	0.6​	0.6​
37​	7.8​	7.7​	0.1​	0.1​
38​	7.7​	7.5​	0.1​	0.1​
39​	7.5​	7.1​	0.2​	0.2​

 

[Huntnful]

Excellent and well detailed post! Yeah basically, hold edge of vitals with the lower wind call and if it gusts you're in the vitals even more hopefully. Live with the outcome of a poor shot at those distances if you decide to shoot in varying wind.

I was just out shooting long range in the wind the other day. A 5 MPH wind can play hell at 1200 or even 1000 yards.

For me to drop a long bomb in the field, I'd need 2 MPH or less to have legit confidence, or I'm getting closer. I shot a buck at 974 yards last year. The faintest breeze from left to right and I had just verified my data at 1100 yards the previous day. You're still hoping for a good shot at those distances when that bullet leaves the barrel. It is no guarantee when shooting across a big canyon. Live with the outcome if its good OR bad, or don't shoot.

 

[LRNut]

Excellent and well detailed post! Yeah basically, hold edge of vitals with the lower wind call and if it gusts you're in the vitals even more hopefully. Live with the outcome of a poor shot at those distances if you decide to shoot in varying wind.

I was just out shooting long range in the wind the other day. A 5 MPH wind can play hell at 1200 or even 1000 yards.

For me to drop a long bomb in the field, I'd need 2 MPH or less to have legit confidence, or I'm getting closer. I shot a buck at 974 yards last year. The faintest breeze from left to right and I had just verified my data at 1100 yards the previous day. You're still hoping for a good shot at those distances when that bullet leaves the barrel. It is no guarantee when shooting across a big canyon. Live with the outcome if its good OR bad, or don't shoot.

Actually, the math above is the portraying a better picture than reality. Suppose your rifle is 1/2 MOA at 1000 yards. You have only 2.5" of vital area "freeboard" before you risk a miss. So even if the wind only changes .25 mph during your TOF and you made a perfect wind call, those bullets hitting on the "wrong side" are going to miss the vitals. To calculate the odds precisely, you would need to consider the group dispersion as well. And to be fair, the wind change over 1 second is not likely to affect the bullet over its entire trajectory, but your odds of making a perfect wind call negate that.

 

[Huntnful]

This was a varying 2-4 MPH wind at 1020 and 1230 yards.

All of these hits are for sure a dead deer IMO. Even with the 6.9" spread of the 1230 yard shots. As long as elevation is good (smaller margin for error) you have at least a 12" wide kill zone on a mule deer for a little variance.

Any decent sized fragmenting bullet landing in this area is a dead buck I think.

I like to kill deer as close as possible, believe me. But the odds of a kill shot at 1000 yards with decent conditions, with a capable system and shooter are pretty good. But never perfect.

Just a general theory in my head is that 800 yards and closer is 100% a dead animal in decent conditions and totally in my control. After that, I need 5% luck for every extra 100 yards lol. A long shot is no guarantee no matter how much I practice. So I try to be mindful.

 

[LRNut]

This was a varying 2-4 MPH wind at 1020 and 1230 yards.

View attachment 491827 All of these hits are for sure a dead deer IMO. Even with the 6.9" spread of the 1230 yard shots. As long as elevation is good (smaller margin for error) you have at least a 12" wide kill zone on a mule deer for a little variance.

Any decent sized fragmenting bullet landing in this area is a dead buck I think.

View attachment 491826

I like to kill deer as close as possible, believe me. But the odds of a kill shot at 1000 yards with decent conditions, with a capable system and shooter are pretty good. But never perfect.

Just a general theory in my head is that 800 yards and closer is 100% a dead animal in decent conditions and totally in my control. After that, I need 5% luck for every extra 100 yards lol. A long shot is no guarantee no matter how much I practice. So I try to be mindful.

Good shooting for sure! 800 sure is easier than 1000. I am concentrating now on being able to hit at 760 in any wind up to a 3 MOA hold and 630 in any wind.

 

[dfanonymous]

As far as there is no limit; there's always a limit, but the math can't quantify nature.

On the kestrel, the average is just that. Your wind 2 however is the peak, which is still averaged. Already, that's a more useful number. Imo, it depends on time of flight, as it could very well be in the middle or a higher wind at max ord could make it a higher peak than your captured.

The guys I compete against, including myself have a higher than 18% wind call to hit success rate.

Marines in my class at sniper school never got a "redo" because wind changed in any testing criteria…and there was a higher than 18% success rate. So clearly, there's an element that exceeds the math. Same with extreme distance. Ko2m comes to mind.

My point being is the math shows it's difficult, but shooters show it's possible all the time. Even under pressure. There's more to it than the math.

 

[Weaver93]

I am by no means a capable ELR shooter, but a friend is a member of a club where guys can shoot in excess of 2500 yards. I went a couple times and found the environmental reads very interesting. One evening all their first reads were all high and much more varied. They are shooting hilltop to hilltop and one really large field on the far side was freshly plowed and apparently that was causing issues. They said in the afternoon as ambient temperature cools the plowed fields give up warmth faster than solid ground causing updraft.

 

[Petey308]

And this just better illustrates how wind is definitely not a constant. It's a changing variable.

For instance, the notion that BC doesn't account for wind drift is false. The reality is ever-changing amounts of wind for the duration of the bullet's flight affects actual drift and POI.

If you have the firing solution calculated correctly, and thus the ToF calculated correctly, with a fully accurate wind reading for the duration of that time of flight, the POI should be as expected. THAT'S the hard part though. It's darn near impossible to get a fully accurate wind measurement for the duration of the bullet's flight. That's why we see things on target that don't reflect to our firing solution. We can only be as accurate as our inputs- that includes ballistic calculations, as well as quality and consistency of our ammo, rifle, and the shooter input and influence to the rifle upon firing it. All of those things affect POI.

For the long range hunter, we need to understand these things and understand if we're going to shoot at animals far away, we need a bullet that produces wide wounding and is forgiving to point of impact errors (shot placement errors). The likelihood of being off a bit due to a miscalculated wind hold, for example, is high. We can compensate for that by picking the best bullet for the job. We can compensate for that as well by practicing and training a lot and developing really good skills at reading the wind. We also need to know our own true limits and stay within them.

 

[LRNut]

As far as there is no limit; there's always a limit, but the math can't quantify nature.

On the kestrel, the average is just that. Your wind 2 however is the peak, which is still averaged. Already, that's a more useful number. Imo, it depends on time of flight, as it could very well be in the middle or a higher wind at max ord could make it a higher peak than your captured.

The guys I compete against, including myself have a higher than 18% wind call to hit success rate.

Marines in my class at sniper school never got a "redo" because wind changed in any testing criteria…and there was a higher than 18% success rate. So clearly, there's an element that exceeds the math. Same with extreme distance. Ko2m comes to mind.

My point being is the math shows it's difficult, but shooters show it's possible all the time. Even under pressure. There's more to it than the math.

18% was the percentage it changed 1 mph in a 1 second period, not the hit rate. I further stated even if it did, half your bullets are still going to hit simply because of the dispersion of your group. I seem to recall Bryan Litz conducting an experiment with an array of wind meters that talked about the same concept - the wind was changing during the TOF.

 

[dfanonymous]

18% was the percentage it changed 1 mph in a 1 second period, not the hit rate. I further stated even if it did, half your bullets are still going to hit simply because of the dispersion of your group. I seem to recall Bryan Litz conducting an experiment with an array of wind meters that talked about the same concept - the wind was changing during the TOF.

I'm just saying. It didn't effect anything in my examples as wind changed 1 mph during flight, at fairly small targets.

Change effects hit rate, like your mentioning in your dispersion of rifle precision. It's IS relative.

Best we can do is get a good average across the board. It's another reason why I personally always mention that timing your shot is a big part of it, so your shot stays within that average capture, or estimation. Sometimes, if not a lot of the time, the high gust is more consistent.

Litz is the science guy for sure, and will quantify and qualify things. That said, Bryan or the AB team has used Emil Praslick in ko2m for wind calling too. There's still a reward for being good, most in professional and semi professional circles do not refute that.