Wind at your back and ballistics

[CPerkins]

I have seen lots of data about crosswinds and the effects on bullets. What if the wind is blowing from directly behind you. I was shooting a 25-06 rem. today with a 20 mph wind I shot 3 shot groups at 100, 200, and 300 yards.
100 was 4" high (normally 2") 200 was 4 inches high, and 300 was 3" low. Thats with a 120 gr factory winchester load. Something doesnt seem right. Just out of curiousity what about if its blowing in your face?

 

[Ballistic64]

Definately not the wind.A 6 or 12 oclock wind wont produce that amount of change at that yardage.Theorectically a perfectly horizontal 6 or 12 oclock wind wont cause any deviation,but of course theres no such thing as a perfectly horizontal wind.There will be up and down drafts,but to produce a 2" higher zero at 100 yds the wind would have to be coming straight out of the ground. /ubbthreads/images/graemlins/grin.gif

 

[Fiftydriver]

Were you shooting in an area that was not flat??

A tail wind that comes down on your shooting position will cause down drafts and lower shot placement.

A tail wind that runs up a hill to your target can cause updrafting that will cause your bullets to hit high.

If your shooting over small hills at midrange you can also see some minor updrafting over these humps as well and cause slight vertical impact increases.

Up and down drafts can raise all sorts of issues so unless your shooting over a perfectly flat range, you can see some effect on target from a tail wind. Generally at 100 yards this is not a concern so if your jumping 2" at 100 yards I would say there is something mechanical to look into or you are holding your rifle in a different manor then before.

What rifle are you shooting, brand and style?

Kirby Allen(50)

 

[Dan B]

Did you have a bipod removed or installed since you last zeroed?