adjusting for wind

[Harpman]

any one have any good online resources for how to understand wind, and adjusting the soule sights we use..for wind speed and shooting distance, something comprehensive....or a book worth buying on this subject..

[waksupi]

I hate to tell you this, but there is no replacement for actual trigger time. Reading will only tell you how someone else does it. Some learn to dope wind well, others, never do. Good luck with it!

[Harpman]

I dont mean replacement time, I meant including Basic stuff about it...I am not familiar with it at all..like how far a 10 mile an hour wind moves a bullet at a certain speed..etc..then would you change setting for the next bullet if shot at 300 yards farther out same wind...stuff like that..

[felix]

The only rule that works for the guns we typically shoot on this board is to always remember one fact: The wind immediately in front of you is much more important than the wind at the target, so compensation must deal with these requirements first and foremost. You can learn a lot by shooting 22 LR at 50 yards. The better the gun, the more you can learn about what the WIND is really doing to you. ... felix

[StarMetal]

In the jacketed long range varmint shooting alot of attention is focused on bullet weight and bullet design. Rich Jamison is very knowledgeable in these areas. Some shooters went to larger caliber rifles and heavier bullet, like using a 243 rather then a 22-250. Rick proved with shooting tests over and over that what he thinks is one of the more important things is TIME. The faster the bullet it, the less time it takes to get to the target, the less time the wind has to act upon it. If you speed up that 22 caliber bullet it will have less wind drift then a heavier 6mm bullet. But then again you can speed up that 6mm bullet too. The other stuff plays into the factor too which I mentioned as bullet design and weight.

Felix is probably right about the wind in front of your bullet. Our cast shooting is for one thing alot slower then high velocity jacketed varmint shooting and the bullets we use are alot less aerodymanic.

In the back of the Lyman Cast bullet book are trajectory table for most the bullets used in their data. It includes wind drift and times of flight also.

Joe

[jhalcott]

http://members.aye.net/~bspen/OddShots.html
do a search on google for shooting in the wind or wind affects on bullet flight. then practice a lot

[StarMetal]

I have a CD disk long range shooting simulater program. In it you use a 223, a 308, and 50 caliber rifle. It gives you all the training...then you go practice. It's pretty cool and not so easy to do the calculations and be dead on. You fellows that are interested in it I'll make copies for a few bucks to cover postage and the disks. Just pm me with your wants and address.

Joe

[sundog]

We have a small bore match twice a month. After high power it's with scopes, and after mil bolt it's with irons. Match is shot at a hunert off the bench. Shooting .22 RF at a hunert can be, naw, IS, informative and VERY HUMBLING! Kinda like shooting high power at 600.... Some days it's just TOO windy to shoot .22 at a hunert. sundog

[KCSO]

Ah yes, then there is round ball muzzleloader at 100 with variable winds. I once won a match by holding 8" high and 22" into the wind and put 5 45 cal balls in the black for a score of 41, the next highest score was a 38 and down from there. Since the wind was coming from left front to rear right I knew from experience that I had to hold high for my rifle and it worked. I wouldn't have gotten the job done without my spotter though. A good spotter who knows wind is invaluable. In this case my first shot was low and to the edge of the black even though I held where I thought I should. My spotter read the shot and watched the grass and told me not only how much to correct, but when to shoot as the wind matched the first shot.

[mparks]

I still use this one to get a rough idea:

http://www.airguns.net/pcb_download.html

[Tom Myers]

Harpman.

There may be "Rule-of-thumb" methods of determining wind deflection values but I don't know of any that really work well.

To accurately predict the amount of bullet deflection due to wind force, one needs to know the muzzle velocity and the ballistic coefficient of a bullet and then use a ballistics calculation program to determine the time of flight to the target in seconds.

The wind deflection is not determined as a direct relation to the time of flight but is rather a function of wind velocity and the difference between the time of flight and the time it would take the bullet to travel from the muzzle to the target in a vacuum.

As an example, a ballistics program will calculate the time of flight for a bullet with a ballistics coefficient of 0.310 and a muzzle velocity of 1227 fps to a target 400 yards (1200 ft) distant to be 1.16736 seconds from the muzzle to the target.

If the bullet were flying in a vacuum and not slowed down by air pressure, the bullet would reach the target in ( 1200-ft / 1227-fps) = 0.97799 seconds.

Now the difference between 1.16736 and 0.97799 seconds is 0.18937 seconds. This difference is also refereed to as "Lag Time"

Multiply that difference or "Lag Time" times the wind velocity to obtain the wind deflection value.

A wind velocity of 1 mph equals a velocity of 17.6 inches per second (ips)
( 1-mile = 5,280-ft x 12-in / 60-min / 60-sec)

10-mph X 17.6-ips x 0.18937-LagTime = 33.33 inches of wind deflection at 400 yards.

The Precision Ballistics software calculates this lag time and then returns either right-angle or 30-degree-direction wind deflection values in both inches and minutes-of-angle at various ranges.

As you can see from the charts posted below, each range requires a different wind deflection compensation in the sight setup.

Hope this helps.

Tom Myers
Precision Ballistics and Records (http://www.tmtpages.com)



http://breeze.linksky48.com/~tommyers/LinkSkyImages/TomeOfFlight.gif

http://breeze.linksky48.com/~tommyers/LinkSkyImages/WindDeflection.gif

[Idaho Sharpshooter]

where can this program be had?

Harpman is referring (I thinks) to BPCR data for his 45-70 (?). BC's are a pain to determine, we have gone to setting up two chronographs at 10 feet and 100yds, 10 feet to get BC's. Will yours figure BC's with that data, bullet weight, and diameter?

thanks,

Rich

[Tom Myers]

Idaho Sharpshooter;

You are absolutely correct in your statement that Cast Bullet B.C.s are a real pain to determine. Precision Ballistics has the capability of determining ballistic coefficients from respective velocities at various ranges. The software is capable of calculating and using up to 5 different ballistic coefficients applicable throughout 5 velocity ranges.

http://breeze.linksky48.com/~tommyers/LinkSkyImages/calc%20multiple%20bc.gif

Another section of the program will also enable the estimation of the ballistics coefficients of jacketed bullets to a high degree of accuracy.


If one does not have the facilities to determine the velocities at various ranges, the software offers a Cast Bullet Ballistic Coefficient Estimator Module that works quite well for nearly all cast bullet configurations except for some of the more radical shapes, and even then, one may arrive at a good comparative estimation.

This Cast Bullet BC Estimator is not yet offered on the website but may be ordered by using the Contact Information (http://www.uslink.net/~tom1/#contactinfo) on the website.

http://breeze.linksky48.com/~tommyers/LinkSkyImages/cast%20bc%20estimator.gif

A complete description and ordering information of the software may be viewed on the Precision Ballistics and Records (http://www.tmtpages.com) website.

http://www.tmtpages.com/

Hope this helps.
Tom Myers