Thursday, January 26, 2012

Shooting through wind

In long range shooting, the ability to shoot through wind separates the boys from gentlemen. Only shooters who can 'read' the wind, can put on the correct dope or appropriate 'hold-off' to compensate for the wind drift. The following lessons will help the shooters understand what I am saying:

  • Understanding minute of an angle (MOA). The scope's turrets are calibrated in MOA clicks and even the iron sights' click is expressed in MOA. For starters, 1MOA is equivalent to 1.047inches at 100yards (1.14inches at 100m). 
  • Understanding the mil-dot and milliradian vs MOA. Most scopes have reticles that are measured/calibrated in milliradian or mil. One mil is equivalent to 3.6inches at 100yards(3.9inches at 100m), 7.2inches at 200yds and so on. When using hold-off aiming technique for example, if you will aim 1mil to the right of the intended point of impact (POI) at a distance of 100m, it follows that the shots will be found 4inches to the right. This is very important when shooting through wind because the amount of drift caused by the bullet can be compensated by using the mil-dot as reference for the change of aim. 
  • Converting wind velocity to MOA clicks. This is a mathematical exercise that is sometimes hated by snipers. MOA (adjustment) = RxV divided by C   (Hmmmmmm. Heading home instead of reviewing your basic arithmetic?)

During training, I usually both use the wind estimation techniques learned in advanced marksmanship, and the use of wind gauge to accurately measure the wind velocity. I would like to point out that shooters must measure wind speed and classify it as either a 'full-value' wind or a 'half-value' wind. In this exercise, I usually wait for stronger winds (10kph-15kph) to come in order to make my practice a realistic one. I put on record the barrel length, bullet data,  wind velocity and position of the sun. There are available ballistics data that can be studied and evaluated by the shooter; but, there is no replacement to the actual data gathering by establishing shot groups under different conditions. When my coach/assistant shouts "15kph wind", I deliver my shot dead-on then measure the amount of drift caused by that wind. (No jerking please!)

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