Advanced Marksmanship Wind effecting Elevation?

[bribassguy]

I would say I am a newb when it come to long range. I bought a CZ455 to practice wind calls... need some help deciding what was going on.

I was at my local range this week and was having something weird was going on. I as shooting out to 300 and was getting some random elevation changes... like 2-2.5 mils.

My best guess it that the wind was messing with me. There are trees on the right and it's pretty open to the left... I am shooting over a little valley with a little creek in the bottom. The wind was switching from tail wind to left to right. I could see some leaves swirling around and getting lifted up. I was shooting at a 6 or 8 disc and could 3 of 5 then would be way high usually up 2 mil, right 2 mil.

Can a tail wind push a bullet up?

 

[TheGerman]

Vertical deflection + variation in 22LR rounds + wind gradients every 6-8 feet in the air that are doing different things (mainly differences in speed and to a lesser degree direction) that you are arcing that 22 bullet through to get out that far + shooting over a valley that could have air pushing up from it (possibly)

With a rimfire, I'd say its more from the variation in the bullet from shot to shot than anything.

 

[Mike_Honcho]

Wind can definitely alter your E call. Last week I was shooting at 500 yards across a draw in big wind: 5 MILS on the gun and a 1 - 2.25 MIL hold in addition too. Under those conditions my E data was 1 MIL low and had to be adjusted. I see E variance in head / tail winds and big wind obliques routinely.

 

[Sheldon N]

Match a couple weekends ago had us shooting on one stage into a draw across a valley. Wind was predominantly L to R but in that draw it turned into a solid 0.5-1 mil updraft. Everyone was missing high, and this was with calibers a lot more wind resistant than a 22.

 

[strikeeagle1]

This may be of assistance in reconciling one component of observed wind effects.

 

[Trevor]

here is another image the phenomenon is call the Bernoulli principal

http://www.thewindisnotyourfriend.com/images/Bernoulli.jpg

 

[Milo 2.5]

Can a tail wind push a bullet up?

IME, theoretically no, unless there is a significant change in terrain. In some ^^ of the posts those changes are present, valleys, canyons, etc.. You had a creek bottom, where as any drainage will affect wind patterns, doubt it lifts your bullet as much as carry it, if your ammo was subsonic target ammo, it started out so slow that tailwinds will carry it, as much as a headwind will knock it down. Then you say it was switching up L-R, now your bullet is dropping as well as carried to the right. Even supersonic 22 ammo will be subsonic by 75 yards and way susceptible to winds.
Here's the kicker, you most likely had greater than an 11mil elevation hold, just say there was a hill on the other side of the creek and the flight path was directly over it. Now you will get bullet lift, wind never stops, if displaced, or changes path, it now must pick up speed to get back into the pattern, so you have an uplift in the wind pattern, and your bullet is in it.
Canyons and select draws create their own set of issues, say wind is 25mph up top, well, if the canyon runs where the wind can come down it, the air that makes the journey down into now picks up speed to make up the distance it has to travel to regain it's spot of where it was, the trip uphill is where the speed is at it's greatest. Now the same wind that comes up to a canyon at a 90 degree angle will most likely not dip into it unless the span is extremely vast, wind cannot turn that fast, explains why when in one and you can hear the wind howling above but not moving around you, you feel like you're in a vacuum<not correct though. The same as a big city street, the wind is howling down it, you dip into a store front that is not deep enough for protection, so it comes in and swirls before exiting making it worse, but a larger one you may protected because it can't make that fast of a turn.
So again back to your dilemma, unless you shot at some point during the day when conditions were the same for a period of time, and you were able to get a baseline of what your actual up dope was supposed to be when it was dead calm, you really have nothing to go off. the left to right wind drove your bullet down, the tail wind carried it, you say a 2 mill variation, well, that is 10" at 300 yards, for 22 LR ammo, I am going to assume you were shooting damn good ammo.

 

[Qazwsx]

for a .22 it could be wind, but also differing velocities between rounds

 

[lte82]

My Kestrel with Applied Ballistics says it does. Here's data on a 147 ELDM @ 2715 fps. There are significant differences in elevation from wind, and significant differences in windage from spin drift.

1000 yards, 10 mph @ 9 oclock: 8.52 mil Elev / 1.98 mil Left
1000 yards, 10 mph @ 3 oclock: 8.25 mil Elev / 1.40 mil Right

 

[morganlamprecht]

My Kestrel with Applied Ballistics says it does. Here's data on a 147 ELDM @ 2715 fps. There are significant differences in elevation from wind, and significant differences in windage from spin drift.

1000 yards, 10 mph @ 9 oclock: 8.52 mil Elev / 1.98 mil Left
1000 yards, 10 mph @ 3 oclock: 8.25 mil Elev / 1.40 mil Right

dont count on that

 

[lte82]

dont count on that

It seems pretty crazy right? Are you seeing anything close to that?

 

[morganlamprecht]

It seems pretty crazy right? Are you seeing anything close to that?

nope, neither is anyone else i know...most everyone i know zero's out Wind speed 1 for elevation data to remove the AJ feature in the kestrel

there was a decent thread on the scout site about it also

 

[Lowlight]

Terrain is the biggest factor effecting elevation.

Wind is like water and Terrain acts like a stream to create turbulence adding to the unpredicatable nature of the movement. (After all it's invisible)

Compare a sandy bottom stream to one full of sticks and rocks, that is what happens when your shooting location as terrain features there or about.

Ditto on the Kestrel, that stuff I turn off ... it's wrong, the real world rarely aligns to those numbers.

 

[lte82]

So ignore changes in elevation due to wind, got it. Same for spin drift or ?

 

[morganlamprecht]

most of the time where i normally shoot its too windy and inconsistent to say "yea, thats spin drift"...this past saturday it was blowing 15-25mph on the tower...coming from 330-530...none of us were having to add elevation shooting over flat pasture to hit a 10" square plate

on sunday it was 5-12 mph switching from 10 to 2 o'clock...we had guys making impacts and follow up impacts with anywhere from .8 right to .5 left during their 60 second-10 shot strings...good luck picking spin drift out of that...i cant lol

 

[Lowlight]

Yes I turn it off, expecially with 3DOF software like AB ... it has no way to actually calculate this and they use a generic flat rate value based on TOF. 1000 = 1 Minute

I ignore SD in 99% of the cases, as noted above the wind, and the shooter is a bigger factor. Most right handed shooters make their own SD with poor trigger control.

I consider it only after 1500m, and wind that is verified less than 2 MPH, even then, not so much.

 

[lte82]

Good deal. Thanks for the info.

 

[TorF]

The difference in elevation data from 3 o'clock and 9 o'clock wind is built in to David Tubb's christmas three reticle. Just look at the elevation difference in the windage dots at range in the reticle. Spin drift is also accounted for.

 

[Gunfighter14e2]

.Can a tail wind push a bullet up?

Yes. It matters little if it's a head or tail wind. What matters is where the river of wind acts on the bullet the most. A side wind most always will require added up, depending the flight time. The stronger the side wind the more up required depending target distance, projo shape, shot speed, angle ect.
Wind is never constant from muzzle to target, It's all about the river of wind, an where that river is flowing within the projo's flight path, during that flight.

 

[SubOptimal]

I love the river of wind analogy. It makes so much sense. What you know is that the water is flowing down stream, otherwise it is a lake and not a river. Yes there is flow within a lake as well. Water coming in and water going out. Now, you can gather certain data about the water flow. Scattering pieces of grass on the surface can give you an idea about how the water is flowing at the surface and some indication of the effects of islands and protrusions into the flow. You will then have some idea of the surface. However, that will tell you nothing about the flow in deeper portions of the river. Again, contour of the bottom, if you can see it, can give you hints. Sticking a propeller on a long stick will tell you even more but unless you do this for every feature on the bottom over your intended path, you won't really know what is going on.
This, is, in reverse, our issue with wind. We are at the bottom of the river. Our propeller is where we are and we can measure velocity at our position. We really don't know what is going on way up there or way out there unless we can look up and see what those bits of grass are doing up there on our bullet path. We have all seen an eddy around a protrusion into the river where the apparent flow at the surface is actually upstream. Same is going on with the air.

The native Americans call him Wind Baby. He is constantly playing with objects he finds along his path and giggles when he can fool us who think we can predict his actions. Make friends with Wind Baby, some days he will play with you, some days he will just laugh.