What percentage of wind adjustment would be made with 16.5mph wind blowing from rear of shooter at 7 oclock to 1 oclock with target at 12 oclock and shooter at 6 oclock at 1000y 900y and 800y? would half wind value be used with this angle or tad more. Forgot to mention values are for .308 with 215g Hybrid at 2,620 fps.
How to calculate windage adjustment in varying angles of wind.
- Thread starter paulT
- Start date
spclark
Gold $$ Contributor
Percentage for direction doesn't change across bullet weights though the amount of correction will; each bullet deserves its own correction based on BC, velocity and distance that then gets factored by the angle of wind.
High-BC bullets moving fast deserve less correction than low-BC bullets moving slower.
Full value is from 9 or 3; no value is 12 or 6; the half-way in-betweens are half-value & if you're quick & able enough to both perceive AND calculate corrections to the eighths between rounds you'll win every match you enter....
High-BC bullets moving fast deserve less correction than low-BC bullets moving slower.
Full value is from 9 or 3; no value is 12 or 6; the half-way in-betweens are half-value & if you're quick & able enough to both perceive AND calculate corrections to the eighths between rounds you'll win every match you enter....
PaulT, There are a lot of good wind charts that give the information you are looking for. Google "bullet drift and wind charts" and you will find a lot of info. All good high power rifle data books contain the charts. The real challenge is that you have to estimate the wind velocity and direction and that is a learned skill that is best learned from shooting with an experienced shooter. Folks that have earned the Distinguished Rifleman Badge are a good source of this knowledge since that type of competition does not allow any sighting shots and the first shot in each stage needs to have the proper wind call.
Consider that the wind speed up off the deck at max ordinate might be 2.5 X the speed at the ground, that the wind speed might vary across the course, that exceeding some critical wind speed threshold may ramp up turbulence from contour effects (trees, berms, etc). Great advice on how to calculate the steady state as a starting point. Seymour
Hello
This is the best diagrammed wind clock i have found which shows the corresponding values for changes in wind direction.
Now this trick is to apply the value and have confidence you are making the right wind call. To do that you need to understand the size of the entire target and the wind values.
The target frame's dimensions (TFD) are 6ft or 72 inches or 6.8moa for height and width
your rifle spec show a 6.1moa for 10mph of wind (wow)
If you were to take a full value wind and put it on the rifle you would have 10min for your call (16.5 x .61moa = 10.065moa)
according to the wind direction chart a 1 o'clock wind is 50% or half the value of our original number which would be 5moa
Here is where the target size comes in if we know the target size is 6.8moa and half is 3.4 we can make an error of 3moa either side and still be on the target.
We know it is not full value 10moa and the wind hasn't changed to a head or tail wind at 0moa what would be our best estimate and still have confidence we would hit the target. If we suspect we have 7 o'clock wind that would translate to 50% of our original wind call or 5moa the TFD would allow for winds to be 8moa or 2moa which is + or - 3moa from our call of 5moa, to hit the target and be scored.
BUT the 5moa call is only correct if the direction change is shown on both the up wind and down wind flags. the wind lags going across the range and its strength may still be greater then 50% but less then full value until the down wind flags have changed in the same direction as our up wind flags.
How do you determine this (look at other peoples targets) if people or being blown out to the 6 ring and or calling for for missed shot you can be assured a change took place
If you don't have to shoot wait for your original condition to come back
Have fun
Trevor
This is the best diagrammed wind clock i have found which shows the corresponding values for changes in wind direction.
Now this trick is to apply the value and have confidence you are making the right wind call. To do that you need to understand the size of the entire target and the wind values.
The target frame's dimensions (TFD) are 6ft or 72 inches or 6.8moa for height and width
your rifle spec show a 6.1moa for 10mph of wind (wow)
If you were to take a full value wind and put it on the rifle you would have 10min for your call (16.5 x .61moa = 10.065moa)
according to the wind direction chart a 1 o'clock wind is 50% or half the value of our original number which would be 5moa
Here is where the target size comes in if we know the target size is 6.8moa and half is 3.4 we can make an error of 3moa either side and still be on the target.
We know it is not full value 10moa and the wind hasn't changed to a head or tail wind at 0moa what would be our best estimate and still have confidence we would hit the target. If we suspect we have 7 o'clock wind that would translate to 50% of our original wind call or 5moa the TFD would allow for winds to be 8moa or 2moa which is + or - 3moa from our call of 5moa, to hit the target and be scored.
BUT the 5moa call is only correct if the direction change is shown on both the up wind and down wind flags. the wind lags going across the range and its strength may still be greater then 50% but less then full value until the down wind flags have changed in the same direction as our up wind flags.
How do you determine this (look at other peoples targets) if people or being blown out to the 6 ring and or calling for for missed shot you can be assured a change took place
If you don't have to shoot wait for your original condition to come back
Have fun
Trevor
BoydAllen
Gold $$ Contributor
For example, if we take a pure headwind as our starting point, that has no cross wind component, and we compare it to a wind coming from one o'clock, the included angle is thirty degrees. The sine of that angle is .5 which when multiplied by the full value of a wind from three o'clock would give you the cross wind component of the wind coming from one o'clock.
Assign a value of one to the radius of your wind clock circle. That will be the hypotenuse of all of the right triangles that you would be working with. Starting from the one o'clock position on the circle, and draw a line at at a right angle to the line from twelve to center from the one o'clock position to meet the twelve to center line, and another from one to center. The length of the shorter line (sin. of the 30 degree included angle) is .5 which when multiplied by 100 will give you the percentage of full value of the cross wind component of a 1 o'clock wind, or you can multiply it by the full value (.5 x FV) to calculate it directly.
Assign a value of one to the radius of your wind clock circle. That will be the hypotenuse of all of the right triangles that you would be working with. Starting from the one o'clock position on the circle, and draw a line at at a right angle to the line from twelve to center from the one o'clock position to meet the twelve to center line, and another from one to center. The length of the shorter line (sin. of the 30 degree included angle) is .5 which when multiplied by 100 will give you the percentage of full value of the cross wind component of a 1 o'clock wind, or you can multiply it by the full value (.5 x FV) to calculate it directly.
XTR
F-TR obssessed shooting junkie
paulT said:
Here is the HUGE point to take away from that wind rose.
From 12:30 to 1:30 the value of the wind nearly triples! And from 1 to 2 it nearly doubles. Think about that with a fishtailing head or tail wind. It makes it very easy to find the 8 ring at 1000 yards.
Now try dealing with that at Raton with it blowing at 10 to 15MPH. :'( pain, pure and simple.
Blaster-37
1000 Yard
Really? By the time you do all the calcs the condition will change. These theoretical calcs are nice but almost always hypothetical because of the variables. Don't bet on it.
Dope your own rig. Get your rig zeroed, shoot the perceived condition, angle and distance to find out what it does with your gun and load. Log that as it is your personal reality with that setup.
Greg
Dope your own rig. Get your rig zeroed, shoot the perceived condition, angle and distance to find out what it does with your gun and load. Log that as it is your personal reality with that setup.
Greg
BoydAllen
Gold $$ Contributor
I did not mean to imply that I calculate but that the results of the calculations can teach us something useful for reading flags. Obviously, by the time that one would take a reading, do the math to correct for angle, and consult a chart for drift, in typical switchy conditions, the wind would have changed. On the other hand, if you are near to a head wind, and paying too much attention to the ribbon, and not enough to the angle of the flag, you could get bit. That can be useful information.
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