The Big Mystery
[B] Reading the Wind and Successful LongRange Shooting[/B]
[B]Part 2[/B]
Ok, so let’s go back and figure it out. This formula is based on a 175 grain .308 bullet at 2700 FPS, and works fine for 168’s as well, I’ll give you some compensation factors later if you shoot something different.
Let’s use a 700 yard target (700 yards is the longest target at Boomershoot, and since we just finished that, it makes the easiest reading!)
Using a 5 MPH wind from 90 degrees, a fairly common angle for us there.
Calculation:
1)700 yards: 7 – 1 is 6.
2)5 MPH wind, since full value is 10, that’s half of full value or 6/2 = 3
3)90 degrees is full value. So 1. 3 x 1 = 3 MOA
3x1 gives us 3 MOA. Compare that with JBM ballistics computer in the same scenario,where we get exactly 3-3.5 MOA, depending on bullet velocity! Awesome!
The method does tend to give us a little bit of cheat on the upper side of value, meaning it tends to overestimate the value a tiny bit, but in my experience, most of us over estimate the actual wind speed a little bit, too, so it works very well in the field.
One more scenario:
500 yards
15 MPH wind
45 degrees
1)500 yards: 5 – 1 is 4.
2)15 MPH is 1.5 times full value so 4 X 1.5 = 6
3)45 degrees is ¾ value, so .75 x 6= 4.5 MOA
Checked against JBM again, which generates exactly 4.5 MOA for a bullet at 2700 FPS!!
But what about other calibers? I did promise a little help there.
Let’s say you shoot a .300 Win Mag:
Simply add a fourth step, and for magnums multiply the result of step 3 by .7, for.338 Lapua mags use .6, and for .50 BMG use .4.
What about smaller calibers like the 5.56 with 77 grain bullets? Well, I’d ask, “Why the heck are you trying to go long with a tool not suited for the job?” Just kidding! Out to about 600 yards you can still use the formula, but in step one simply don’t subtract the 1 from your yardage estimation.
You can use the formula with just about any caliber, but you might want to run some numbers in JBM, compare them against the .308 numbers, and figure your own compensation step for step 4.
You will have noticed I only talked about 100 yard increments. I did that on purpose, because they are the easiest to figure, and I’m lazy! But….for targets under 25 yards farther than an even 100 yards, use the formula, from 25-75yards further, add in ¼-1/2 MOA, and for those beyond 75 yards, use the next 100 yard calculation.
There is one last issue that we should address, and that is heat and altitude.
The formula is based on normal atmospheric conditions. Say Sea Level to 4000 feet or so, and zero to 90 degrees or so. If you are higher than that, or warmer,you can try adding a fudge factor in step one, and use Range – 2 instead of Range – 1 .
Remember what I said back at the beginning about having read dozens (hundreds?) of articles on wind reading? There are so many because this isn’t an exact science, winds are tough to solve, and if you could solve them, the conditions would change before you had a chance to implement them! Practice with the formula will make you better, though!
Finally, I’m not smart enough to have figured out this formula all by myself. Jeff Hoffman, the owner of Black Hills ammunition came up with the formula, and must be credited with it, it isn’t widely used to my knowledge, but it is the best formula and explanation I’ve found.
[B] Reading the Wind and Successful LongRange Shooting[/B]
[B]Part 2[/B]
Ok, so let’s go back and figure it out. This formula is based on a 175 grain .308 bullet at 2700 FPS, and works fine for 168’s as well, I’ll give you some compensation factors later if you shoot something different.
Let’s use a 700 yard target (700 yards is the longest target at Boomershoot, and since we just finished that, it makes the easiest reading!)
Using a 5 MPH wind from 90 degrees, a fairly common angle for us there.
Calculation:
1)700 yards: 7 – 1 is 6.
2)5 MPH wind, since full value is 10, that’s half of full value or 6/2 = 3
3)90 degrees is full value. So 1. 3 x 1 = 3 MOA
3x1 gives us 3 MOA. Compare that with JBM ballistics computer in the same scenario,where we get exactly 3-3.5 MOA, depending on bullet velocity! Awesome!
The method does tend to give us a little bit of cheat on the upper side of value, meaning it tends to overestimate the value a tiny bit, but in my experience, most of us over estimate the actual wind speed a little bit, too, so it works very well in the field.
One more scenario:
500 yards
15 MPH wind
45 degrees
1)500 yards: 5 – 1 is 4.
2)15 MPH is 1.5 times full value so 4 X 1.5 = 6
3)45 degrees is ¾ value, so .75 x 6= 4.5 MOA
Checked against JBM again, which generates exactly 4.5 MOA for a bullet at 2700 FPS!!
But what about other calibers? I did promise a little help there.
Let’s say you shoot a .300 Win Mag:
Simply add a fourth step, and for magnums multiply the result of step 3 by .7, for.338 Lapua mags use .6, and for .50 BMG use .4.
What about smaller calibers like the 5.56 with 77 grain bullets? Well, I’d ask, “Why the heck are you trying to go long with a tool not suited for the job?” Just kidding! Out to about 600 yards you can still use the formula, but in step one simply don’t subtract the 1 from your yardage estimation.
You can use the formula with just about any caliber, but you might want to run some numbers in JBM, compare them against the .308 numbers, and figure your own compensation step for step 4.
You will have noticed I only talked about 100 yard increments. I did that on purpose, because they are the easiest to figure, and I’m lazy! But….for targets under 25 yards farther than an even 100 yards, use the formula, from 25-75yards further, add in ¼-1/2 MOA, and for those beyond 75 yards, use the next 100 yard calculation.
There is one last issue that we should address, and that is heat and altitude.
The formula is based on normal atmospheric conditions. Say Sea Level to 4000 feet or so, and zero to 90 degrees or so. If you are higher than that, or warmer,you can try adding a fudge factor in step one, and use Range – 2 instead of Range – 1 .
Remember what I said back at the beginning about having read dozens (hundreds?) of articles on wind reading? There are so many because this isn’t an exact science, winds are tough to solve, and if you could solve them, the conditions would change before you had a chance to implement them! Practice with the formula will make you better, though!
Finally, I’m not smart enough to have figured out this formula all by myself. Jeff Hoffman, the owner of Black Hills ammunition came up with the formula, and must be credited with it, it isn’t widely used to my knowledge, but it is the best formula and explanation I’ve found.
You seek escape from pain. We seek the achievement of happiness. You exist for the sake of avoiding punishment. We exist for the sake of earning rewards. Threats will not make us function; fear is not our incentive. It is not death that we wish to avoid, but life that we wish to live. - John Galt