Tuesday, May 27, 2014

Weather Effects Refresher

Wind, temperature, and precipitation can affect the trajectory of the bullet. In addition, all weather conditions have a physical and psychological effect on you too. These are things you should take into consideration because we all know the sun ain't shining everyday and the wind is always blowing somewhere. This is just a refresher in case you need it. 

The most important thing to do before you shoot is to read what's going on out in front of you so you don't compromise your position or send one down range that is just off the mark when you need it to count. The information below is for the .223 / 5.56 AR15 rifle with A2 irons, my personal choice of sights. Your experiences may vary depending on variation of the AR you shoot, but the information about the weather still applies.

Physical Effects

The weather condition that presents the greatest problem to shooting is the wind. Wind affects a bullet's trajectory. The effect of wind on the bullet as it travels down range is referred to as deflection. The wind deflects the bullet laterally in its flight to the target.

Deflection of a Bullet

The bullet’s exposure time to the wind determines the amount the bullet is deflected from its original trajectory. Deflection increases as the distance to the target increases. 

There are three factors that affect the amount of deflection of the bullet: 
Velocity of the wind—The greater the velocity of the wind, the more the bullet will be deflected.

Range to the target—As the distance to the target increases, the speed of the bullet slows allowing the wind to have a greater effect on shot placement. 

Velocity of the bullet—A bullet with a high muzzle velocity will not be affected by the wind as much as a bullet with a low muzzle velocity.
Determining Windage Adjustments to Offset Wind Effects: The velocity and direction of the wind in relationship to the bullet must be determined to offset the wind’s effects. If you can classify wind values and determine velocity within 5 mph, you can effectively engage targets in windy conditions.

Wind Direction: Determine wind direction by observing direction vegetation is moving, by feeling the wind blow against the body, or by observing direction of a flag on a pole, if you have that luxury...

Wind Value Classifications: Winds are classified according to the direction from which they are blowing in relation to the direction of fire. The clock system indicates wind direction and value. Winds can be classified as half value, full value, or no value. THE TARGET IS ALWAYS LOCATED AT 12 O'CLOCK!!!

Wind Velocity: There are two methods used to determine wind velocity: observation and flag. The flag method is used as a training tool for known distance to learn the observation method. This method teaches you to relate the effect a given wind condition has on the natural surroundings in order to develop the base of knowledge used during the observation method.

The observation method is the primary method used to estimate wind velocity and direction in a tactical situation. The following are guidelines used during the observation method:
Under 3 miles per hour (mph) the wind can hardly be felt on the face. The presence of a slight wind can be detected by drifting smoke. 

3 to 5 mph winds can be felt lightly on the face.
5 to 8 mph winds keep tree leaves in a constant motion.

8 to 12 mph winds raise dust and loose paper.
12 to 15 mph winds cause small trees to sway. 16 to 25 mph winds cause large trees to sway.

Flag Method
The flag method is primary method used on a known distance range. To estimate wind velocity in miles per hour: Estimate the angle created between the flagpole and the flag in degrees.

Divide the angle by four to estimate wind velocity in miles per hour.

Information given is based on a dry flag, as a wet flag will be heavier and give you a false reading.
Windage Adjustments  
After identifying wind direction, wind classification, and wind velocity, windage adjustments needed to enable the bullet to strike the target are estimated in the following ways: 
Observation Method
Using the windage chart provided below, match the wind velocity, wind direction, and range to the target to the information in the chart to estimate the correct number of clicks to apply to the windage knob.

Flag Method

Using the windage chart provided below, match the wind velocity, wind direction, and range to the target to the information in the chart to determine the correct number of clicks to apply to the windage knob. Once the number of windage clicks is determined, turn the windage knob causing the rear sight aperture to move into the direction of the wind.

Use this information as you will. But hopefully, you'll put it to good use, and improve your skill set. I see guys with those fancy 45 degree angle irons hanging off their rifles and I'd bet that most of them couldn't use them past 50 yards, let alone 300 if they had to. You will not always be able to count on that red/green dot optic you paid up to $500 for.
This will help you actually use them when that time comes.

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