When shooting over valleys, you are shooting blind. If the wind is moving left to right at your location and moving left to right at the target, it makes sense to assume it is moving left to right in the middle and probably a bit more briskly. I have shot some thousand yard matches which were shot across a valley but we were allow unlimited sighters so it was possible to get a pretty good handle on wind. I can tell you that my attempt to send up a helium balloon mid-range did NOT work! Correlating point of impact to indicators at each end did work but also seemed to work better for a lot of others than it did for me
Wind deflection vs. displacement
- Thread starter cody c
- Start date
Glock4ever
CGN Ultra frequent flyer
- Location
- Edmonton, AB
If it makes you feel better... In the artillery, there are a lot of high end instruments employed to attain the highest levels of precision to reduce the probable errors in deflection and range. Log books, chronographs (used for each shot), survey equipment to ensure that the location of the guns and target are known, met balloons to know atmospheric conditions from the surface of the earth to apex of the bullets trajectory, ballistic computers that tie all of this information together, etc are just some of the tools that are used to give good reliable predicted data. But at the end of the day, the data is just that "predicted" data. Very rarely, do we get "target" rounds on the first shot. Trying to build the "ultimate" system that will get dumb rounds to hit the target at these distances is likely impossible because of all of the variables that can affect that bullets flight. It is also the reason why the artillery has moved towards smart munitions. Basically projectiles that can self-correct their flight path enough to guarantee a target hit.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Pros and cons to terrain and it really depends on the prevalent winds in your area - direction and intensity.
In this location I am above the valley bottom by say 200ft... there are no trees any where near me so I am pretty much shooting in "clean" air. If you imagine a bullet traveling higher and then dropping into the other mountain side, there isn't really any terrain feature that can screw up the winds for you. And shooting has proven it runs pretty true.
You CAN see mirage in this location. you just need to set up the right glass to make it happen... alot of scopes like S&B make this very hard. Others like Sightron make it easier. You can measure the wind at the rifle, compare the way the trees are moving and then see how that compares to the destination. Assume the middle is consistent.... A bit of mental gymnastics and a good SWAG and a shot is sent
Go off the impact and put shots on target. Remember/monitor the wind cues for changes and adjust accordingly. On a typical day, the wind here stays pretty steady for direction so you are only adjusting for velocity... it actually gets pretty easy after a while. bigger bullets help of course.
Here is another spot I shoot at and where the road bends your bullet goes over a valley. here the wind comes into the valley in a variety of directions and intensity, swirls and gusts. There are plenty of up and down drafts as you are low enough to see the affect.
On some days, it feels like you are shooting a shotgun BUT you get to see alot of wind in a short time and that is how you learn.
I really want to see the mirage and put alot of effort into optics that make this happen. A few flags, some trees and you can get a pretty good idea of what is happening.
Jerry
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If you want to understand how wind effects things, Google vector addition.
Vectors need both velocity and direction, and by adding wind vectors to your projectile vector you can get some semblance of how things will change... one problem would be figuring out how much force is applied by the wind on your specific projectile, as this would vary with changes in bullet weight and design.
As for the question of whether the wind causes a change in position vs a change in angle, its a mix of both. In a frictionless environment it would change the angle of flight, but due to air resistance that change in angle will decrease with time.
A third factor is that we are actually talking about acceleration changes and not velocity changes which is even more complicated...
Vectors need both velocity and direction, and by adding wind vectors to your projectile vector you can get some semblance of how things will change... one problem would be figuring out how much force is applied by the wind on your specific projectile, as this would vary with changes in bullet weight and design.
As for the question of whether the wind causes a change in position vs a change in angle, its a mix of both. In a frictionless environment it would change the angle of flight, but due to air resistance that change in angle will decrease with time.
A third factor is that we are actually talking about acceleration changes and not velocity changes which is even more complicated...
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Jerry,
Our shooting location is more like your first picture where we shoot elevated, and into a hillside across the valley.
The direction of wind is typically from left to right, not always, but pretty close to perpendicular.
I believe depending on this direction, the wind can be down drafting (coming over the hill and dropping into the valley due to low pressure areas), or vise-versa going from the valley and up the face of the hill in high pressure areas. We see some elevation wondering at times. Rarely bad. That's when we pack up or chill for awhile. Rounds down range are impossible to gauge.
Generally we see variable wind from 4-9 MPH. Sometimes bursts up to 12ish, but pretty rare.
I was quote stoked the day we moved from 640y to 850y. In a 10 MPH cross wind I told my shooting buddy to hold 10MOA. He hit the 12x12 on the first shot. Now this doesn't seem impossible, but in our location it's rare to get that in our area with a stiff breeze.
We find the required wind calls in certain conditions between 450y to 650y with 308's are massive. Going back to other discussions going on, if a 6/6.5 makes this easier, is it really better? What we learn between these two distances can be extrapolated to 850, and 1000. If these distances becoming "easier", we'd want 1200-1500y. Something that's nearly impossible to find here.
For that reason I'm going to rebarrel my rifle with a 30cal - 308 chambering.
Our shooting location is more like your first picture where we shoot elevated, and into a hillside across the valley.
The direction of wind is typically from left to right, not always, but pretty close to perpendicular.
I believe depending on this direction, the wind can be down drafting (coming over the hill and dropping into the valley due to low pressure areas), or vise-versa going from the valley and up the face of the hill in high pressure areas. We see some elevation wondering at times. Rarely bad. That's when we pack up or chill for awhile. Rounds down range are impossible to gauge.
Generally we see variable wind from 4-9 MPH. Sometimes bursts up to 12ish, but pretty rare.
I was quote stoked the day we moved from 640y to 850y. In a 10 MPH cross wind I told my shooting buddy to hold 10MOA. He hit the 12x12 on the first shot. Now this doesn't seem impossible, but in our location it's rare to get that in our area with a stiff breeze.
We find the required wind calls in certain conditions between 450y to 650y with 308's are massive. Going back to other discussions going on, if a 6/6.5 makes this easier, is it really better? What we learn between these two distances can be extrapolated to 850, and 1000. If these distances becoming "easier", we'd want 1200-1500y. Something that's nearly impossible to find here.
For that reason I'm going to rebarrel my rifle with a 30cal - 308 chambering.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
If you can, put up flags at the crest of these hills and watch what happens. Temp changes will cause Massive difference in outflow winds... just shoot at Homestead to see that silliness.
You haven't indicated the weight of bullet being shot but assume they aren't very heavy.... I have gone very heavy in my FTR with 230gr bullets. At 1000yds, the difference in drift/bounce vs lighter bullets is very obvious. The key is controlling and tuning for something this heavy but I am getting there.
You might find a whole lot less fuss if able to launch a 208/210gr bullet. The Hrn 208gr Amax was a gem for ELR shooting... I hope the new ELD-M will share similar traits.
Having a 6XC, 22's, and having shot 6.5's, 7's, 30's for years, you can really see the benefit of heavy bullets as distances increase. Not necessarily more accurate but less likely to move off course.
I was doing some testing with the binary targets at 800m... hitting the container with the 308/230 was way easier then the 6XC/105 in gusty/bumpy winds.
If you are going to rebuild and want to move away from the 308, consider a mid case 7mm. The 300WM is also alot of fun
But the 308 and the right bullet will happily travel out to a mile without much fuss.
Enjoy the journey.
Jerry
You haven't indicated the weight of bullet being shot but assume they aren't very heavy.... I have gone very heavy in my FTR with 230gr bullets. At 1000yds, the difference in drift/bounce vs lighter bullets is very obvious. The key is controlling and tuning for something this heavy but I am getting there.
You might find a whole lot less fuss if able to launch a 208/210gr bullet. The Hrn 208gr Amax was a gem for ELR shooting... I hope the new ELD-M will share similar traits.
Having a 6XC, 22's, and having shot 6.5's, 7's, 30's for years, you can really see the benefit of heavy bullets as distances increase. Not necessarily more accurate but less likely to move off course.
I was doing some testing with the binary targets at 800m... hitting the container with the 308/230 was way easier then the 6XC/105 in gusty/bumpy winds.
If you are going to rebuild and want to move away from the 308, consider a mid case 7mm. The 300WM is also alot of fun
But the 308 and the right bullet will happily travel out to a mile without much fuss.
Enjoy the journey.
Jerry
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
If you are using RL17, have you tested the change in your LR accuracy with changes in ambient conditions?
That could be a large reason your groups show varying degrees of vertical... yes, wind is there but maybe your load tuning is also changing?
We will not use RL17 in competition because of this. H4350 is vastly more stable. The new IMR 4451 seems to be getting some positive feedback... haven't personally tested yet so can't say.
The further you go, the more sensitive your loads are going to be with change. If you have access to a labradar or magnetospeed or better chronie, this would be an ideal time to compare velocities vs ambient and see what is happening.
Sometimes a shot that goes way out may also show up as a big change in muzzle velocity.
You got to cover all the possibilities.
Jerry
That could be a large reason your groups show varying degrees of vertical... yes, wind is there but maybe your load tuning is also changing?
We will not use RL17 in competition because of this. H4350 is vastly more stable. The new IMR 4451 seems to be getting some positive feedback... haven't personally tested yet so can't say.
The further you go, the more sensitive your loads are going to be with change. If you have access to a labradar or magnetospeed or better chronie, this would be an ideal time to compare velocities vs ambient and see what is happening.
Sometimes a shot that goes way out may also show up as a big change in muzzle velocity.
You got to cover all the possibilities.
Jerry
I have with RL17, however it doesnt vary so much during the day, but more by outting.
I always think I need more testing, but facts show this has been the case. Hence my second load of Bergers (w/ varget). Problem is I have a pretty good backing of RL17 and 208's.
I'll do some research. Might grab some H4350 and run some tests. Thanks for the tip.
I always think I need more testing, but facts show this has been the case. Hence my second load of Bergers (w/ varget). Problem is I have a pretty good backing of RL17 and 208's.
I'll do some research. Might grab some H4350 and run some tests. Thanks for the tip.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
Change is change and if that is with your load tuning... that is very bad.
You need the confidence to be able to use your past info to figure out what to do going forward. If the data is varied, how do you guess what you need to adjust at present?
In F class competition, we need to be able to trust what we do here is going to work in another place with possible big swings in ambient. With our varied weather, you need to feel confident with the morning that has frost on the ground, and the afternoon, you are broiling in your shorts and T shirts.
Many powders simply do not handle these changes well
Jerry
