Fig. 43
The score-books issued by the Ordnance Department have windage charts that have been carefully worked out and all you have to do is this: Estimate the force of the wind in miles per hour, and determine the direction from which it comes (whether a 9 o'clock wind, a 2 o'clock wind, etc.). Then look at the windage chart and see just how much windage you must take.
The simplest and best rule for the beginner is for him to make his estimate and then ask an experienced shot what windage to use, checking this up with what he found on the windage chart. In this way he soon learns to estimate for himself.
Practice estimating the wind. Ask a man who has been making 5's and 4's what windage he used and check up with your own estimate.
You can find out the direction of the wind by watching smoke, grass or the limbs of trees.
Throw up some small straws and watch which way they are blown, or wet your finger and hold it up. The wind cools the side it strikes.
A 12 o'clock wind slows up the bullet and a 6 o'clock wind helps it along,—so, in the first case you would need more elevation and in the second less elevation.
[1392]. The zero of a rifle. The twist of the bullet given by the rifling of the barrel causes the bullet to move to right, which movement, called "the drift," is compensated by having the slot in the rear sight for the drift slide, slope to the left. However, in some rifles the compensation is too great and in others it is not enough.
That reading of the wind gauge necessary to overcome the drift of a rifle at a particular range is called the "zero" of that rifle for that range, and all allowances for wind should be calculated from this reading.