## Wind Invisible But Decisive

Full-size Leica Geovid 7x42mm binoculars are both great glass and an excellent laser rangefinder.

A distinguished rifleman once told me, "A plinker studies trajectory tables; a master studies the wind." His point was well taken.

While accurate range estimation is absolutely essential, most long-range shooters learn to judge distances and compensate correctly. They know it's important, so they do it.

But that leaves the other great factor of longrange accuracy—wind estimation—and here is

U.S. Marines in Iraq with Designated Marksman Rifle and Vector laser ranging system.

 RELATIVE WIND EFFECTS Soon after publication of The Ultimate Sniper in 1993, I received letters critical of how I'd explained wind effects and their required compen sation. Having never seen other than the stylized illustrât 'ons in military manuals, the writers insisted I had it wrong and, for instance, a 45-degree wind was 1/2 value, not the 3/4 value I'd described. (Though that's incorrect, it would seem logical since 45 is half of 90, or half of a full-value wind.) So that you can see exactly what these values are, here's the multiplier factor table used by Sierra Bullets, which verifies my original data. Wind Angle to Required Bullet Path Multiplier 0 Degrees 0.000 5 Degrees 0.087 10 Degrees 0.174 15 Degrees 0.259 * 20 Degrees 0.342 25 Degrees 0.423 30 Degrees 0.500 ** 35 Degrees 0.574 40 Degrees 0.643 45 Degrees 0.707 *** 50 Degrees 0.766 55 Degrees 0.819 60 Degrees 0.866 65 Degrees 0.906 70 Degrees 0.940 75 Degrees 0.966 80 Degrees 0.985 85 Degrees 0.996 90 Degrees 1.000 **** * 1/4 value ** 1/2 value *** 3/4 value **** Full value

similar to that of the higher winds but turned around as it passed down the gorge.

The presence of such contradictory winds is far more frequent than most people realize. We sensitize sniper students to their presence by posting crepe paper streamers every 100 yards on our 1,000-yard known-distance range. They're initially surprised to find that winds at the distant firing line are steady and left to right, while mid-range winds are gusting and right to left.

It's only by looking closely that they notice the firing line overlooks an expanse of flat, open ground—which causes the steady wind— while there's a service road that cuts through thick woods at mid-range—hence an opposite, gusty wind.

Your challenge as a sniper is to learn where to look to detect evidence of winds so that you can determine exacdy the directions of any winds in your sector. Having determined direction, you then must estimate wind speed, which equally demands attention to minute details.