Range Report Need a good wind drift formula

[dcaven]

I am new and apologize if this is posted somewhere else. I didn't see it so I will ask. I have found several formulas for wind drift but all seem to lack one thing or another. I would like a formula that takes into consideration ballistic coefficient and bullet weight. Also, I am not afraid of trig but will need some explanation for which lines to apply to which part of the formula (which is the hypotenuse, etc.) I want to learn this by hand before I go out and buy any gadgetry. Thank you.

David

 

[dcaven]

Re: Need a good wind drift formula

By the way, I am shooting a .270 with 140 gr Nosler Accubonds that have a BC of .496.

 

[marksman25]

Re: Need a good wind drift formula

Try Bryan Litz book on applied ballistics.

 

[tobias]

Re: Need a good wind drift formula

The formula for the deflection d is:

d = w (t-t_0)

w: constant cross wind
t_0: time of flight without drag, t_0 = x/v_0 with range x and muzzle velocity v_0
t: actual time of flight

The formula was derived by the French ballistician Didion.

 

[blklabs]

Re: Need a good wind drift formula

I can understand wanting to know the formulas behind the magic, however for real world use, just go to jbm, input your data, and get your dope. Then go validate that by shooting.

 

[damoncali]

Re: Need a good wind drift formula

If I read you right and tob's (correct) answer is not what you're looking for, there is no simple wind drift formula. What you need is actually a system of differential equations that define the bullet's overall movement (in three dimensions). They're simple equations (if you can ever call calculus simple), but you can't solve them on paper (at least I can't, and I'm not aware of anyone who can) - you'll need to use a ballistics program.

Unless you're really into math and programming, this isn't a case where you need to learn it on paper before you start using computers. Get a copy of Bryan Litz's book, which explains the concepts better than I've seen anywhere else and use a program to get the numbers.

If you are really, really into math and programming, get a copy of Modern Exterior Ballistics by McCoy. It tells you everything you need to know, but you'll need a background equivalent to an engineering degree to understand all the math.