SHOOTERS : Doping Wind?

skeeter

Unverified
Joined
Apr 23, 2008
Messages
319
Location
Chattanooga, TN
I'm starting to look into long range shooting. I understand bullet drop, but I have a very small understanding of how wind effects bullets and how to compensate for it... can anyone explain this to me?
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
The best way to view the effects of wind is to think of your bullet as a football. When you throw a football and the wind is blowing from right to left, you throw the football into the wind. This way the wind will push the football to the desired receiver.

When calculating wind, you have to determine first what direction the wind is traveling. This is in reference to your location to the target. Using a clock method, the target will be at the 12 ‘O’ clock position.
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
The reason we must understand the direction of the wind, is b/c it directly impacts the value of the wind. If the wind is blowing right to left (3 to 9 ‘O’ clock) it would be considered a full value wind. If the wind is blowing at an angle say 1 to 7 ‘O’ clock it would be considered a 1/2 value wind. These are the values of the wind reading you take. Meaning if you are getting a reading of a 10MPH wind and it is at a 1/2 value, you would only adjust for 5 MPH of wind (the 1/2 value of the actual wind).
usamuclockx370.gif
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
Now getting the wind reading can be done using several different methods, observation, mirage, feeling and the pointing method are the most common methods.

0-3 mph: Wind hardly felt, but smoke drifts
3-5 mph: Wind felt lightly on the face
5-8 mph: Leaves are kept in constant movement
8-12 mph: Raises dust and loose paper
12-15 mph: Causes small trees to sway
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
(A) There is smoke or dust nearby, allowing you to measure the wind by how fast it is drifting, or (B) It is a hot day and there is an object with a well defined horizontal edge near the target on which you can see the mirage. "Mirage" refers to the heat waves which rise off of hot objects. It is easier to observe in a 50x spotting scope than in a 10x rifle scope, but it is still visible. You can see it with your naked eye if you look across the hood of your car on a hot day. In still conditions, heat waves appear as wavy vertical lines. Five mph winds bend them over at about a 30º angle while ten mph winds bend them over at about a 60º angle. Fifteen mph winds bend them over flat so it is no longer feasible to measure the wind speed this way. If you look at a horizontal edge, like a rooftop, the heat waves seem to be running along it.
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
If there is a large parallel component to the wind (it is blowing mostly towards or away from you), then the angle of the mirage still measures the perpendicular component of the wind, but the parallel component will make the heat waves wiggle. This is called a "boiling" mirage and is a difficult shot because a wind's direction shifts more often than it's magnitude shifts, causing the perpendicular component to vary more rapidly than if the wind were mostly perpendicular, and those changes are hard to see because of the wiggle. In cases like this it is not possible to dial your windage up and down fast enough to keep up with the variations in the wind, so you should set your scope for the least wind that you are seeing and then fire the next time the wind dies down.
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
Condition (A) is easy to obtain at any public range because there are always lots of people blasting away at fifty and hundred yard targets. Condition (B) is easy to obtain at rifle matches because you can look at the target boards. In combat, condition (A) is obtained in bombed out cities while condition (B) is obtained in still intact cities. You must practice with both.
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
Unfavorable conditions are when neither (A) or (B) are obtained, in which case you have to resort to looking at the greenery. Roughly, when grass sways and leaves flutter, there is a five mph wind. When tree branches sway, there is a ten mph wind. When small trees sway, there is a fifteen mph wind. What is most unfavorable about this technique is that the swaying of tree branches tells you nothing about the direction of the wind. For that you need another technique, the best one being to throw some grass up in the air. If 0º is perpendicular to your shot and 90º. is in line with the target (it doesn't matter if it is towards you or away from you), then assign full value to any wind from 0º to 45º. Assign half value to any wind between 45º and 75º. Ignore winds between 75º and 90º
 

skeeter

Unverified
Joined
Apr 23, 2008
Messages
319
Location
Chattanooga, TN
Ok that helped me out A TON! the wind values really helped! Thanks:). Is there any mathmatical solution on the adjustment for certian wind readings? I know the wind will be different at the target than it is at the location of the shooter.
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
Well first you have to understand Minute of Angle or MOA.

Minute of Angle: A minute of angle (a term used to discuss shot dispersion) is the standard unit of measurement used in adjusting rifle sights and other ballistic-related measurements. It is also used to indicate the accuracy of a rifle. A circle is divided into 360 degrees. Each degree is further divided into 60 minutes; therefore, a circle contains 21,600 minutes. A minute of angle is an angle beginning at the muzzle that would cover 2.54 centimeters at a distance of 91.4 meters. When the range is increased to 182.8 meters, the angle covers twice the distance, or 5.08 centimeters. The rule applies as range increases-7.62 centimeters at 274.2 meters, 10.16 centimeters at 365.6 meters, and so on.
image1665.jpg
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
Increase of Shot-Group Size: Just as the distance covered by a minute of angle increases each time the range increases, a shot group can be expected to do the same. If there are 2.54 centimeters between bullets on a 25-meter target, there will be an additional 2.54 centimeters of dispersion for each additional 25 meters of range. A 2.54-centimeter group at 25 meters (about 3.5 minute of angle) is equal to a 25.4-centimeter shot group at 250 meters.
image1666.jpg
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
Then you will need to know the deflection in MOA’s to the particular bullet at distance and wind velocity.

For example: 10MPH full value L-R at 200 yards with M855 is 2MOA deflection, meaning your bullet will be pushed 4 inch off center zero to the right. (so you would adjust 2MOA to the left)
 

skeeter

Unverified
Joined
Apr 23, 2008
Messages
319
Location
Chattanooga, TN
Ok... So if I understand what you are saying this will come with shooting the same bullet weight and powder charge and learning what my rifle will do at different distances, from there I can log what happened and use it next time I have the same variables.
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
No, it is easy to pull the data from the net or where ever else… I just can’t give you data with out knowing what bullet you are using… ;)

First things first, learn how to call the wind correctly. The rest is easy! ;)
 

skeeter

Unverified
Joined
Apr 23, 2008
Messages
319
Location
Chattanooga, TN
Ok I understand... And before I ask for data I will need to get a rifle capable of shooting long ranges and figure out what bullet I'm using... lol :uhh:
 

Diamondback 2/2

Infantry
Verified Military
Joined
Jan 24, 2008
Messages
6,848
Location
Tejas
SSMP
Military Mentor
Well the deflection rate will very from ballistics, so yeah you will need to figure out what set up you want first.

Most of the data out there for LR guns are going to be on .308 and 300WM. I would start with your budget, then move onto the type of rifle you can afford to shoot (not just buy). A lot of people buy rifles they can not afford to shoot, in LR shooting you can expect to spend $1 to $1.50 a round for good quality ammo.
 
Top