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Old 10-04-2010, 08:28 AM
Mr. 16 gauge Mr. 16 gauge is offline
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Question Adjusting for windage?

O.K., I have a question.....how does one account for windage in long range shooting: is there some means of making calculations, or is it just a WAG (wild ass guess)?

I understand that you can determine the amount of hold over necessary to hit a target at a certain distance based on the bullets B.C., velocity, zero, ect, but what about windage?

Is there a formula, such as "a bullet weighing X amount traveling at velocity Y zeroed at 200 yards needs to be held to the left at Z inches from the bulls eye for a wind from the right at 12 mph"?......something along those lines? Or is it just "I held about 6 inches to the right....because it felt like I should"?

Working on planning a pronghorn hunt for next fall....there are no 'long range' shooting ranges here in MI (leastwise none I can find), so a lot of this 'long range' stuff is going to be based on calculations.

Thanks in advance...........
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Old 10-04-2010, 09:42 AM
bigbrother bigbrother is offline
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Unfortunately, there's not a cure all or "cheat" for shooting in the wind. But there is most certainly a way to calculate wind drift and it's done the same way you calculate "hold over" or elevation adjustment.

In order to determine either you need a ballistic calculator. You can buy one, download one, or use a free site but one is necessary to determine drop and drift. (of course you can do it all on paper if you get the formulas but it's way too much math for me!) They do have a number (exbal/jbm) you can put on your smart phone and change it for real time or in the field calculations! here's the one I use: http://www.mega.nu/traj.html

I'm assuming that your simply looking for inches of holdover and inches of drift which you'll find when talking to long range shooters is not the advisable or acceptable way. When shooting past 500 yards, we are making actual adjustments to our scopes and holding on where we want to shoot or at least using a mil dot reticle to have a precise aiming point. But for the sake of the post we'll talk inches and hold over out to 500 yards.

If you have your calculator you next need to now a number of things: the true bc of your bullet, the actual velocity your rifle is shooting your ammo, for this you need to shoot a minimum 10 shot string over a chronograph to get an average, the elevation you will be hunting at, and an expected temperature you will be hunting in. All of this goes into determining drops and drift. In the calculator, you will be able to pick a wind speed for a drift computation. Picking 10mph is typically the simplest that way you can go up or down in your head easier in multiples or 1/2's. Once you know all of these things, plug the info into the calculator and it spits out a ballistic chart giving you inches of drop and drift in increments out to however far you want. (ie every 25yards from 100 to 500 yards)

NOW, first thing to remember is that the chart values are for a FULL VALUE (crosswind blowing 90deg to line of sight) wind. Next, you need to know the actual wind speed, licking a finger doesn't cut it. So, you'll need a Kestrel wind meter or something similar to determine speed and direction. So for sake of simplicity lets say you're shooting a 30-06 with a 180g bullet with a bc of .435 and a G7 drag, hunting at 6500 feet in elevaiton on a 45 degree day. The computer says you need 9.94" of drift compensation at 500 yards in a 10mph crosswind. But it's blowing 15mph!!!! Now what? Multiply 10" (round up cause you can't hold .06" off anyway) by 1.5 and now you need 15" of hold off.....if it's 20mph you need 20".

In reality that's a very simple and probably not "real life" situation. More than likely you'll be shooting in wind other than full value. There's not enough room to explain all of the intricises of shooting in the wind but here's a boiled down version. If the winds in your face or at your back (0 value wind), to 500 yards don't worry about it, make your elevation correction and concentrate on making a good shot. If the wind is blowing at a 45 to your line of sight (1/2 value) you will need 75% of your drift value. (this varies slightly but to 500 yards it's negligent) If it's blowing from say 1:00, 11:00, 5:00 or 7:00 use 50% of your drift.

There are other circumstances you may encounter, especially when shooting further than 500 yards that you need to consider as well. Such as the wind blowing multiple directions ie, one way where you're at, the complete opposite where the target is. Maybe even 3 ways or 3 values between you and your target. The most important however is the wind from where you're at to 1/2 way to the target. This wind typically has the most effect on your bullet.

Again, when shooting to 500yards, knowing the wind speed where you're shooting from and the effect that wind has on your bullet is most important. Even a small wind deflects a bullet alot. I know I rambled a little bit but I hope it helps...
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Old 10-07-2010, 07:05 PM
Ridge Runner Ridge Runner is offline
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Here is my method, I have a ballistic program called exbal on a PDA which I have with me in the field, in that program all my load data is loaded permanently.
When I get on site I add the following data
Barometric pressure
tempature
wind speed
exbal then asks from which direction its blowing (in hours on a clock face)
I enter all this data when I set my gear up, if game is spotted in another direction than anticipated I must change wind directio)
when I prepare for a shot, the game is ranged, and angle of fire in 's is entered, and the range, exbal gives me my comeups and wind dope.
I adjust my scope and take the shot when its offered. Beyond 1000 yards I will almost always take a spotter shot to be sure I've got all my data right.
as I'm glassing I mentaly check the wind for changes in speed and direction, sometimes ya gotta refigure in your head for gusty conditions or swirling winds, this part only comes with practice.
RR
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Old 10-08-2010, 08:54 AM
bigbrother bigbrother is offline
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LOL...TECHIES! We only get to use the exbal with Petey decides to tag along, he keeps that stuff tight to his chest! It's something that all long range shooters should invest in. Being able to actual real time data into the program, it gives you instant feedback on adjustments....another supreme confidence builder.
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Old 10-08-2010, 02:54 PM
skeet skeet is offline
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You know all that wind drift stuff is no matter how ya put it just a WAG. Or pretty much is where we do most of our hunting for speed goats. Ya might actually get close though. In any of the really long range shootin if the wind is blowing pretty good over here..over where the critter is it may just be a LOT different...even the opposite way. and if it's blowin 30 here it may only be 10 over there. I had one of those exbal programs on a palm..takes too much time on spooked game. Neat for constants though. And I was still kinda guessing some. Almost bought another one not long ago.. But I did an about face on my shooters lately and figure I'll buy the rifles first..the other stuff later....and keep on guessing...LOL
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Old 10-22-2010, 05:20 PM
Catfish Catfish is offline
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I have a drop and wind drift chart on my long range guns. About any program will work for figureing drop as you should field check all of them befor you hunt with them. Wind drift is an art more than a science. I carry a wind meter, but tells me only the the wind speed where I am standing and I have seen 4 flags in 100 yards all pointing in different directions. Long range shooting takes a good rifle scope that track accurately, a range finder, a wind meter, accurate rifle and practice. High BC bullets, heave for caliber bullets are a big plus but you will need a barrel with a faster than normal twist to stablize them.
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