# Wind effect on bullet.



## PrepConsultant (Aug 28, 2012)

I said before I would post the wind calculation I use for long range shooting. As those of you know, I LOVE to shoot long range. I did not come up with this but it is one of the better and easier to remember ones I have found. The amateur is concerned with trajectory, the professional is concerned with wind effect.. The person that taught me also has several articles in mags and a website I will post if I can find it.. This calculation is for the 175gr .308 but I will also tell you the conversion for the 5.56,300 win mag, 338 LM and 50 BMG.

There are 3 steps. 
First is you make your calculation based on a 10mph full value wind effect.
Adjust for actual wind speed
then adjust for actual wind value. 
This is very simple once you get used to it and you will be able to do it in your head very quickly.
The formula is range in yards expressed as a single digit. minus 1. So 700yds is 7 minutes of correction-1. 500yds is 5 minutes then minus 1. 

Next is actual wind speed. A 20 mile an hour wind will affect the bullet twice as much and a 5 mph wind will affect it half as much.
So if you have a 700 yd target with a 5 mph wind. It will go like this 700 yds (7minutes-1 = 6) Then since it is only a 5mph wind you divide the 6 by 2 and have a 3 minute correction at 700yds. 

Next is actual wind value.A lot of places teach only no value,half value and full value which will get you on a man sized target out to about 600yds but to get further or more precise, I prefer this.\
15 deg is 1/4 val
30 deg is half val
45 deg is 3/4 val
65 deg is 9/10 val
90 is a full value

So, if you have a 700 yd target with a 5 mph wind at 45 deg(3/4 value) It will look something like this 700yds (7minutes-1=6) then since it is a 5mph wind we cut the 6 in half to get 3. Then with the actual wind with the 3/4 value we multiply the 3 x .7 = 2.1 so you would round to a 2 MOA hold or dial...The actual calculation would be .707 but you don't have to be that detailed. 

Remember, you are starting off with your range-1 with a 10mph full value effect then adjusting from there. This is for the .308 175gr. It works ont he 168 pills out to 600 or so then gets a little wide. It becomes very easy with practice. Also If you are shooting at say 635 I would round it down to 600 so 6-1 then the rest of the calculation..

If you are shooting 
5.56 77 grain ammo you would use range=moa not minus 1 so 700yds is 7 then rest of calculation. You do everything the same except don't minus the 1. This also works out to about 600yds or so.
Next is the 300 win mag. so you can add one more step. The 190 grain 300 wm bullet is affected .7 times as much as the .308 so in the step 4 you would just multiply your calculation by .7 
The 338 Lapua is affected .6 times so you would multiply whatever you get by .6
And then finally the 50BMG is .4 so you would just multiply by .4.

I hope this helps. Like I said, I didn't come up with this but it works very good and is the one I use most of the time. It is VERY easy to do in your head and can also be done very quickly.. Just make sure you know your wind speeds and ranges and you will be reaching out there and touching someone..


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## Montana Rancher (Mar 4, 2013)

Let me break this down to layman's terms

If you target is over 400 yards hold over his head and if you have a crossing wind, hold 1 "head width" into the wind at 400 yards and 3 "head withs" at 500 yards and 8 head withs at 600 yards for every 10mps of cross wind.

With this said unless you shoot long range as a habit, don't shoot over 400 yards in any kind of wind.

Read the last line and repeat after me, unless you shoot long range as a habit don't shoot over 400 yards.

I know of few people under field conditions that can reliably shoot over 400 yards, of course I am talking hunting conditions which is the perfect scenario, pressure, altitude, temperature, position, which is all the variables that apply.

We don't have to wait for them to be within 50 yards as in the civil war, but the closer they are the better chance you have of a good shot, I would suggest that untrained personell start shooting at 100 yards.


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## PrepConsultant (Aug 28, 2012)

This is for the guys that really like to shoot long range. I agree with you about most shots out to 400 yds. Although I did kill my deer a deer at 505 this year. This is for the ones that want to start taking things out a little farther than normal.. As for untrained shooting at 100yds. I couldn't agree more. But then you want to start taking it out further and further. When I was in boot camp for the Corps. They took us out to 500 with iron sights..

When you become comfortable, you should start taking it further and further. Are most of your shots going to be long range? Not at all. But it is good to know you can take them. My hobby is long range and it is very fun. It is also pretty expensive but what hobbies aren't?

You said not to shoot long ramge in any kind of wind. Some people don't have that choice and some people want to learn how. This formula is for that. It is hard to go out and not have any wind and I'm not the kind of guy to sit home on a great day just because of some wind.. It is all a matter of what someone is interested in doing..


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## Rigged for Quiet (Mar 3, 2013)

Good info but only part of the equation if you are not shooting in a static environment like a range of your back 40 that you know inside and out.

I'll dust off the brain cell and throw some info out there about determining range (albeit with a mildot), determining what your wind speed is so you know what number to use to begin with using both mirage (usually needs a spotting scope) and natural surroundings techniques, and last but not least the natural lateral drop of your bullet due to spin, range, temperature, yada yada yada.


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## Seneca (Nov 16, 2012)

There was a time when I belonged to a club that had a 1000m range, as I recall I usually shot at 500m. over time and numerous trips to the range I got a feel for different situations inclement weather wind etc. and became fairly handy with an M1A1 using iron sights out to 500m. Thing is I was not under any pressure, I was able to make my observations over many trips and time and I developed a sense of the rifle/cartridge performance and my own limitations. 

I am firmly convinced that closer is better. Could I make a 500m shot? more than likely. Would I take a 500m shot? not if I had better options. I get the whole thing about long range calculations. I really do! Yet I opted for the more pedestrian approach and use the practice and observation approach. Wash rinse repeat, It's fun-er that way.


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## PrepConsultant (Aug 28, 2012)

You are not always goin to get the 500yd or shorter shot. This is for the guys that WANT to shoot at longer distances..


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## Gunner's Mate (Aug 13, 2013)

Great Information, I shoot F-Class usually about 135 or so with an AR 15 in 6.5 grendel and I can say it always the wind the beats me . cant wait to try this formula out


PrepConsultant said:


> You are not always goin to get the 500yd or shorter shot. This is for the guys that WANT to shoot at longer distances..


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## PrepConsultant (Aug 28, 2012)

Gunner's Mate said:


> Great Information, I shoot F-Class usually about 135 or so with an AR 15 in 6.5 grendel and I can say it always the wind the beats me . cant wait to try this formula out


 Have you shot the 6.5 creedmore yet?


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## Gunner's Mate (Aug 13, 2013)

Yeah I have 6.5 Creedy but Im taking the barrel off and putting on a 260 AI barrel I reload and want to fire form 260AI brass out of 308 brass


PrepConsultant said:


> Have you shot the 6.5 creedmore yet?


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## Gunner's Mate (Aug 13, 2013)

and I really Like the 6.5 grendel its my favorite AR platform its wicked accurate I ve put it on the steel out to 1100 yards. When im at shoot all the bolt guys are floored by how good a gas gun shoots


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## PrepConsultant (Aug 28, 2012)

I agree, the grendel is one of the best rounds in the AR platform and even other than AR it is a great round. I also like the 6.8 spc and am goin to be getting one in an AR platform along with a 300 blk with a can... The 260 is an excellent round for long range also. I haven't shot it myself but a very good friend shoots it almost daily..I'm not sure of the terminal ballistics of the 260 but I know it will reach out there..


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## Gunner's Mate (Aug 13, 2013)

I really like the 6.5 caliber rounds started out with 6.5 X 55 swede years ago then a pre 64 Mod 70 264 Win mag, back in the day bullet selection was really limited for reloaders but now its off the hook my next build is the 260 ackley improved / 6.5-08 AI, im not sure how the bullet selection for 6.8 / 270 is but the 6.5 is really great for the handloader


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## PrepConsultant (Aug 28, 2012)

I have heard great things about the 260 AI..


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