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Long range wind

 
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  #1  
Old 03-01-2006, 12:24 AM
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Join Date: Nov 2001
Location: Wyoming
Posts: 92
Long range wind

Living in "Windy Wyoming", doping the wind is obviously a concern with any shot over about 100 yards... even with a belted magnum! Of course I have the "toys" to determine distance and wind speed, but is there some advanced (or simplistic) gizmo on the market to precisly determine wind direction? I realize that wind where I'm shooting from vs. where I'm shooting to will be different, but close helps when you can't judge the wind by the waving of the sage brush.
Many thanks for all help and input.
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  #2  
Old 03-01-2006, 01:17 AM
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Location: Pueblo, CO
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Re: Long range wind

I use a Speedtech.com watch when i go afield. It has been partly responsible for a couple successful long-range shots just this year on coyotes. As far as the wind direction goes, i just approximate that at full value, 1/2 value, or 1/4 value.
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  #3  
Old 03-01-2006, 02:01 AM
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Join Date: Nov 2001
Location: Wyoming
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Re: Long range wind

What I've been looking at is the ballistics program readouts for an 800y shot with a 15 mph cross wind. 180gr Scirocco @ 3200 fps. Full value is (according to the program) 43.3" of drift, half value is 30.6" and quarter value is 16.2". Either my program's all wet, or it's not an exact ratio of wind angle to shot angle to figure drift. I'm contemplating trying to make a weathervane with 5 degree increments, but I'd far rather just throw some money at a gizmo if I can.
Thanks for the input though.
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  #4  
Old 03-01-2006, 04:33 AM
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Re: Long range wind

I cant remember exactly how this one guy was doing it, but he was doing it by pointing the way to the target, then drawing the way the wind was going, then multiplying by some number to get the direction. Its something like that. It kinda reminds me of maybe a triangular trick, draw a line to the target, then draw a line the way the winds blowing and you'll get some kinda angle, then you multiply or divide by a certain number or degree, damn I cant really remember. I remember the guy from shooters.com, his name was LRnut. I dont remember the whole process, but he said it worked for him. If anybody else kinda knows what I'm talking about, I'd be interested in it as well. I was shooting at 1150 yards today with a 10-15 mph wind with a 180g btip at 3300fps. For the first 600 yards or so, the wind was going to the left pretty good, but after that, the terrain was different and it was more of a tailwind.
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  #5  
Old 03-01-2006, 06:59 AM
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Join Date: Dec 2005
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Re: Long range wind

Long range highpower rifle competitors have been using a simple formula for about 90 years at ranges from 600 to 1000 yards. It goes like this: range (in hundreds of yards) times wind speed (in mph) divided by 10 equals minutes of angle correction for a full value wind.

A full value of wind is one from either 3- or 9-o'clock relative to the line of fire. Half-value winds were from 1, 2, 4, 5, 7, 8, 10 and 11-o'clock. And a no-value wind was from "supper time" (6-o'clock) or midnight (12-o'clock). This method worked pretty good firing the old M2 173-grain boattail machine gun bullet from .30-06 Springfield M1903 and M1 Garand rifles. It at least got one on the 6-foot square target paper when winds were pretty strong.

With more recent cartridges shooting bullets that buck the wind a lot better, I've came up with a bit more realistic formula using the same type of simple math. And winds from 1, 5, 7 and 11 are really true half value ones (the sine of 30 degrees is 0.5). Winds from 2, 4, 8 and 10 are really closer to 90% ones (the sine of 60 degrees is 0.87).

1. Use a very good software program for ballistics such as that sold by Sierra Bullets to calcuate the wind drift for your bullets for each hundred yards of range you'll shoot at.

2. For each hundred yards of range, convert the bullet's drift in inches for a 9-o'clock 10 mph wind to minutes of angle (MOA).

3. Multiply each hundred yards of range times 10, then divide that number by the drift in MOA number for that range. The answer is your "magic number" for wind corrections at that range. Note the longer ranges will have smaller magic numbers than shorter ranges.

In use, you'll need something to measure wind speed. There's many types available from the simple Dwyer Gage to fancy, expensive digital electronic windmills. Then laser or estimate the range. Multiply the range in hundreds by the wind speed in mph then divide that answer by your magic number for that range.

Example: range is 600, six times indicated wind speed of 4 mph is 24 and dividing 24 by your magic number of 16 (Sierra 30 cal. 180-gr. SBT @ 3000 fps at 3000 ft elevation) equals a 1.5 MOA correction for a full-value 4 mph wind. If the wind's from 4-o'clock, 90% of 1.5 MOA is about 1.25 MOA, so make a 5 quarter-minute click correction to the right, aim, hold very still then take your shot.

I've used magic numbers for .264 Win. Mag, .308 Win., .30-.338 Win. Mag with much success. It's nice to read my old Dwyer wind gage, do the mental math for a .308 Win. shooting 155-gr. bullets out at 3050 fps at 6000 ft. elevation in a 20 mph crosswind then make the correction on a receiver sight that has 1/5th moa clicks fire the first shot at the 1000 yard target and miss the letter "X" in the center of the 10-inch diameter scoring ring by about half an inch. But then there's been times when I missed it by a couple of feet 'cause the downrange cross winds weren't the same speed as the wind at the firing point.
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  #6  
Old 03-01-2006, 07:37 PM
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Re: Long range wind

Bart,

Was shooting today and was serious enough that I put up a wind flag well more of a wind indicator than a flag. Thend during the course of shooting and making the 200yd trip to the target holder I got to thinking, which is usually a bad thing, for me...

I was wondering if wind from 90 degrees = 100% then is wind from 45 degrees = 50% effective for the same wind speed.

If I read your post correctly the impact wind with respect to angle varies as the cosine of the angle. Am I understanding correctly??

I also googled on Dwyer Gage. Hey those things are plenty spendy!! Already have GPS for elevation so I think I'll just add one of those windmill thingers for wind speed.

However, you lost me completly on the "magic number" [img]/ubbthreads/images/graemlins/blush.gif[/img]

I'll follow your example and do a little figuring and see if I can sort it all out.

Appreciate the post, thanks...
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  #7  
Old 03-02-2006, 12:41 AM
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Join Date: Feb 2003
Location: Pueblo, CO
Posts: 1,173
Re: Long range wind

Roy-- take a look at the Windtronic anemometer-- i picked mine up fairly cheap-- google them, or maybe just google anemometers period. Might find something even cheaper.
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