Wind effect at 550 yards on 175 gr Berger

[Galveston22]

I am trying to learn how to shoot F-Class on my own. I want to know how much of a hold off is needed for a 10 mph 90 degree crosswind at 550 yards with a .308 Berger 175gr Match Target BT Long Range bullet at 2600 fps assuming a 100 yard zero. According to JBM Ballistics its 20" of wind drift. Does that mean its a 20" hold off of the bullseye? Just seems like a lot to me.

http://img171.imageshack.us/img171/374/jbmm.jpg

[savageboy]

Sounds right to me.

[johndoe3]

You're probably right, but I would put in 0.0 target speed to minimize multiple corrections.

[trappst]

I just ran it through the online hornady calculator....not sure if this is right but 20" would be way too little of a correction.

Looks like 500 is 46.3" and 600 is 70.8"

assuming I read that right....bc of .264 and fps is 2600 right?

[Galveston22]

I just ran it through the online hornady calculator....not sure if this is right but 20" would be way too little of a correction.

Looks like 500 is 46.3" and 600 is 70.8"

assuming I read that right....bc of .264 and fps is 2600 right?


Notice that it is G7 bc not G1

[Galveston22]

You're probably right, but I would put in 0.0 target speed to minimize multiple corrections.


The correction for target speed is under the column "Lead" and is completely seperate from wind speed.

[trappst]

ooooops, forgot about that little g1/g7 thingy.....

using the Berger ballistic calculator

drift at 550 yards= 24.6"


sorry for the confusion, no experience with a 308 at all!

[savageboy]

"Just seems like a lot to me".
And Hence why I went w/ a 6.5mm long skinny bullet!

[Budweiser360]

Talk to any F-class shooter and he will tell you that they do not hold off anywhere outside the V-bull ring. If you are looking to hold off for that much wind, you will not find your scores near the top. You need to make your adjustments and only hold off as little as possible. Remember, aim small, miss small.

Also, if you were able to get 2700-2750fps out of it, you will have that much less drift.

[memilanuk]

Talk to any F-class shooter and he will tell you that they do not hold off anywhere outside the V-bull ring. If you are looking to hold off for that much wind, you will not find your scores near the top. You need to make your adjustments and only hold off as little as possible. Remember, aim small, miss small.

Actually... thats not *entirely* true. There are some top echelon (as in US F/Open team) shooters who hold off as long as they can keep the x-hairs on the target face. This requires a few things to be true... 1) shooting in light-to-moderate winds, 2) a high-magnification scope that allows you to hold off on small details on the target face, and 3) shooting something other than a .308! ;)

Personally I tend to dial in a base windage - if the flags or a wind meter tell me there is approximately 10-12 mph full value cross wind, then I dial on the appropriate amount number of MOA, and shoot my sighters. If I need to dial more to get in the X/10 ring, I do so. After that... I hold off inside the X/10 ring (or V/5 for the Brits and Canucks), and sometimes into the 9 ring... but beyond that I will dial the necessary MOA on or off my base windage setting and then hold center again. This works better if you keep a plot sheet and record a) what windage/elevation changes you make and when (as in 'which shot') you make them, b) where the shot actually fell on the target face, and c) where you actually broke the shot. If you don't plot your shots or at least jot down sight changes, you better be absolutely sure you can remember where you started and where you ended up. Shooting a .308 at long range on a very windy range... a 'small' change is made in moa (as in whole or half) and its not unheard of to make changes between shots in *revolutions*. Not plotting shots on a range like that is death, plain and simple.

The next fun thing to learning to read the wind with a .308 is coming to term with the angular effects on the wind deflection.