When hunting with a scoped rifle, how exactly do you measure wind?

I mean hοw dο уου judge hοw much thе wind wіll mονе уουr bullet?

Tags: exactly, Hunting, measure, Rifle, scoped, wind

2 Responses to “When hunting with a scoped rifle, how exactly do you measure wind?”

1. Mr.357 says:

   June 16, 2011 at 2:16 pm

   I always measure wind in miles per hour, and it doesn’t matter if I am shooting with a scoped rifle, open sight rifle, or sitting in the yard. If you are asking about how to estimate the wind speed, you have to learn how much different speeds of wind affect different items found in nature.
2. The Ghost of Harrison says:

   June 16, 2011 at 2:32 pm

   I figure the wind in increments of 10 MPH, and extrapolate the windage correction from previous tests.

   Let’s say I know that in a 10 MPH crosswind from 9 o’clock, the wind moves my bullet . 75 inches at 100 yards (3/4 MOA) (That’s about what you can expect a . 308 firing 168 grain SMK with a 21 inch barrel to get- At least if its my rifle).

   Now the first thing to say is that at 1000 yards, the same deflection is going to happen, but ten times the amount, right? Wrong: It ends up being not 7. 5 inches, but closer to 100 inches (over 12 MOA! : or 48 clicks on a 1/4 MOA dial).

   The problem is here: wind not only causes continual acceleration- just like gravity, but is also time dpendant (not distance dependant) (again, just like gravity).

   On shorter range calculations you can get pretty close simply adding the MOA error found at 100 yards for every additional 100 yards. That is, if I know I’m going to be . 75 inches to the right at 100 (3/4 MOA), I can figure pretty much on being 3 inches to the right at 200 (1 1/2 MOA, or double the error in terms of angle from 100 yards), and 6 1/2″ to the right at 300 yards (2 1/4 MOA or 3 times the error at 100 yards).

   However, as the bullet slows down, the correction tends to increase proportionally, and by 500 yards this rule of thumb is no longer useful. The correction for that same bullet at 500 yards ends up being not 3 3/4 MOA (18. 75 inches), but 5. 5 MOA (27. 5 inches). (Again, that’s from my own data book, so no copying!): Meaning if I was to rely on the calcualtions from my “rule of thumb” alone, I’d now be off target by nearly 9 inches! (At 500 yards, 9 inches aint half bad, but it is enough to cause problems when shooting a 19 inch wide silhouette, especially when human error is added to the mix).

   The proper way to do it would be to calculate the acceleration due to wind for the amount of time the bullet is expected to be in flight. For me at least, this is beyond the sort of mental math I can do on the fly (your results may be better), so I refer to a chart built from direct experience. There are some really good ballistics calculators available that will do it for you too: the best of these wil let you input your own observed data from your actual shooting experience and adjust their equations accordingly. Honus makes an especially trick watch that can be programmed to do this.