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Old May 9, 2020, 03:21 PM   #1
cdoc42
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Windy question

My hunting club recently erected a 1000 and yard range, which stoked my interest.
I made some wind flags and today I put the first two at 400 and 800 yards just to see how well they work. It is a VERY windy day.

At 400 yards the wind was blowing from directly behind me and at 800 it was simultaneously 90 degrees to the left compared to the 400 yard marker.

If the wind was to the right at 400 and to the left at 800, which one has more influence on the path of your bullet if I am targeting the 800? I thought I remember a bench rest shooter telling me the closer wind flag has more influence on your bullet but I also tend to think the bullet is slower as it nears 800 compared to 400 so the further flag may be more influential.

What say you experienced long range shooters?
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Old May 10, 2020, 10:52 AM   #2
Bart B.
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Wind in the first third of target range has 2 times or more effect as wind in the last third. Sierra's software calculates this......



Note the crosswind speed is faster above the line of sight than in it. The highest point in bullet trajectory is about 55 percent of target range. It varies with the terrain.


Last edited by Bart B.; May 10, 2020 at 11:38 AM.
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Old May 10, 2020, 12:11 PM   #3
tangolima
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You want to pay attention to the wind close to you than far out. Cross wind builds up lateral speed to the projectile. Speed times time equals distance.

-TL

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Old May 10, 2020, 06:58 PM   #4
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Tangolima, that agrees with what the bench rest shooter told me but he was only shooting at 100 yards with 3 flags -25-50-75 yards.

Bart B. I don't understand the graph. IF both shots are fired with the same bullet and speed, why would the shorter range drift so dramatically starting at 100 yds while the other doesn't drift until over 700 yards?
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Old May 10, 2020, 08:07 PM   #5
Bart B.
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Quote:
Originally Posted by cdoc42 View Post
Bart B. I don't understand the graph. IF both shots are fired with the same bullet and speed, why would the shorter range drift so dramatically starting at 100 yds while the other doesn't drift until over 700 yards?
One bullet (red) has a 10 mph cross wind drift from the muzzle to 333 yards then no cross wind from 334 to 1000 yards.

The other bullet (green) has no cross wind from the muzzle to 666 yards then a 10 mph cross wind from 667 to 1000 yards.

Bullets drift in a horizontal curve when wind blows on them. When the wind stops, they go straight in the direction they were going at that time.

Last edited by Bart B.; May 10, 2020 at 10:33 PM.
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Old May 10, 2020, 11:46 PM   #6
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Maybe I'm wrong, but looking at the graph it appears the red line, when the bullet is going faster from muzzle to 333 yards, drifts about 9 inches.

The green line, with no wind until 667 yards, is then going slower, and drifts about 16 inches when it travels the final 333 yards.

The graph lists the velocity at 2650 fps, If that is muzzle velocity it can't be the same velocity at 666 yards. I interpret this graph to mean the slower bullet is affected more by a 10 mph cross wind.

Although it's difficult to evaluate the graph with precision, with respect to more effect of the wind in the first 3rd:

The red line drifts 1 inch in the first 100 yds; in the last 100 yards it drifts from 2.5 to 7 inches, or a drift of 4.5 inches

The green line, in the first 100 yards of wind exposure at 666 yards, drifts about 2.5 inches in that first 100 yards and from about 8" to 16" -or 8", in the last 100 yards.

That would suggest the greatest effect is in the last, not the first, third of travel. Am I reading this wrong at 12:45 Am?
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Old May 11, 2020, 07:23 AM   #7
std7mag
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Maybe this will help..

Shooting is all about angles.
One MOA at 100 yards is roughly 1 inch.
At 1,000 yards it is roughly 10 inches.
So say the wind blows the bullet off it's path by 1 inch at the 50 yard mark.
That would equate to 2 inches at 100 yards, and 20 inches at 1,000 yards.
If the wind would blow the bullet off it's trajectory by 1 inch at 900 yards, then theoretically it would only be 2 inches off at 1,000 yards.
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Old May 11, 2020, 07:45 AM   #8
Bart B.
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Quote:
Originally Posted by cdoc42 View Post
The red line drifts 1 inch in the first 100 yds; in the last 100 yards it drifts from 2.5 to 7 inches, or a drift of 4.5 inches

The green line, in the first 100 yards of wind exposure at 666 yards, drifts about 2.5 inches in that first 100 yards and from about 8" to 16" -or 8", in the last 100 yards.

That would suggest the greatest effect is in the last, not the first, third of travel. Am I reading this wrong at 12:45 Am?
Several things end up causing total wind drift at target range. That's what we correct for making windage adjustments on sights.

Note the red bullet keeps drifting right from the line of sight about 5.2 inches every 100 yards past the first 333 yards after the wind stops deflecting it at 333 yards.

Bullet horizontal trajectories are straight when there's no cross wind. Whatever angular rate to the LOS they're drifting at when the wind stops is maintained until there's more wind.

The green bullet's wind deflection is calculated using its velocity at 667 yards.

Last edited by Bart B.; May 11, 2020 at 08:33 AM.
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Old May 11, 2020, 08:25 AM   #9
cdoc42
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std7mag: "So say the wind blows the bullet off it's path by 1 inch at the 50 yard mark.
That would equate to 2 inches at 100 yards, and 20 inches at 1,000 yards."

It's probably not that simple, if you look at the chart. The red line drifted 1 inch at 100 yards and as Bart pointed out, even after the wind stopped, by 1000 yards the bullet drifted almost 45 inches.

Bart,regarding the statement that the wind effect is greater during the first third as compared to the last third of flight, examine that red line again. During the first third the bullet drifted 9 inches. Even though the ind stopped completely the bullet continued to drift as you pointed out, but during the last third -from 666 to 1000, the drift was an additional 15" (26 inches at 666 and about 41 at 1000= 15).

Complicating that, it is unlikely that the wind would totally stop over 1000 yards, and I have experienced that it changes from left to right or vice-versa as well. I just started long range shooting and a companion was doping my shots. At 1000 yards I aimed at the left edge of the 18" plate and my shot went about a foot off the right edge for about a 30 inch drift. I moved 12" to the left and the next shot went into the dirt off the left edge! Finally, after another 3-4 shots I made a bullseye at 1000 yards but I have no confidence that it was my skill!!

Yesterday it was a really breezy day, probably at least 20mph here and I had a wind flag in the back yard. It changed direction constantly from north to west and immediately to east. Bad day to shoot, but what are the chances wind changes lke that even at 5 mph?
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Old May 11, 2020, 08:59 AM   #10
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Remember we adjust windage to correct for the total effects on target of all cross winds. Even subtle winds under 6 mph can fishtail right to left. Observe and correct for only the upwind conditions. And every shot we make ends up reflecting our abilities to correct for environmental variances.

I've shot 1000 yard matches and flags on both sides of the range at zero, 200, 300, 500, 600, 800, 900 and 1000 yards each revealing different wind speeds and directions. A couple flags showed no wind. Focus your spotting scope to see mirage heat wave's speeds and directions at different ranges.

Most windage correction for first shot at long range was 28 MOA on the 800 yard line. Used 25 to 35 MOA for 800, 900 and 1000 yards
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Last edited by Bart B.; May 11, 2020 at 12:33 PM.
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Old May 11, 2020, 12:50 PM   #11
Bart B.
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Quote:
Originally Posted by std7mag View Post
Shooting is all about angles.
One MOA at 100 yards is roughly 1 inch.
At 1,000 yards it is roughly 10 inches.
So say the wind blows the bullet off it's path by 1 inch at the 50 yard mark.
That would equate to 2 inches at 100 yards, and 20 inches at 1,000 yards.
If the wind would blow the bullet off it's trajectory by 1 inch at 900 yards, then theoretically it would only be 2 inches off at 1,000 yards.
I disagree. To do that, bullets would have to maintain the same velocity all the way to the target. Instead, they slow down due to air resistance. Bullets with higher ballistic coefficient slow down less.

Starting velocity into each range band is slower. 2 to 3 times faster at the muzzle than at 900 yards. Time of flight from 900 to 1000 yards is much longer than muzzle to 100 yards. If bullets slow down enough, they'll go subsonic.

Have you ever used trajectory software?

Last edited by Bart B.; May 13, 2020 at 07:03 AM.
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Old May 11, 2020, 06:10 PM   #12
cdoc42
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" Focus your spotting scope to see mirage heat wave's speeds and directions at different ranges."

Can you expand on that? If I shoot at 600, then 800, what do I look for in mirage rather than wind flags?
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Old May 11, 2020, 06:55 PM   #13
Bart B.
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Quote:
Originally Posted by cdoc42 View Post
" Focus your spotting scope to see mirage heat wave's speeds and directions at different ranges."

Can you expand on that? If I shoot at 600, then 800, what do I look for in mirage rather than wind flags?
Focus the spotting scope about half to two thirds of target range. You can see heat waves wrinkling across the field of view. They're the same as the mirage waves wrinkling across hot roads or dirt fields.

They will cause the target to blur and wiggle a little sideways. More wiggles means faster cross winds.

I'll try to find a link showing them.
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Old May 11, 2020, 07:03 PM   #14
cdoc42
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That will be welcome. When I put the flags out today at 400-600-800 and 900 it became apparent that watching any of them might well be futile. The wind at any spot was changing direction constantly at anywhere from less than 5 to as much as 15 mph and none of the flags were flying in the same direction as the others. I pictured the bullets moving like some guy going through 4 turnstiles at a train location.
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Old May 12, 2020, 06:06 AM   #15
Bart B.
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This should help....

https://bulletin.accurateshooter.com...potting-scope/

It's best to have someone help you directly.

Yes, bullets wiggle through turnstiles so to speak. If you're behind someone shooting,you can watch the bullet trace to the target.

Last edited by Bart B.; May 12, 2020 at 06:12 AM.
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Old May 12, 2020, 10:46 PM   #16
cdoc42
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That is a great link, Bart B., thanks! My spotter is a previous Army guy with a great interest and knowledge superior to mine who also happened to be the reason I got involved in this hobby at age 77. He does direct my traffic and is primarily responsible for my success at achieving a bull at 1000 yards. My wind post is a reflection of our experience of changing wind directions over the 1000 yard course. Your contribution to this situation is genuinely appreciated.
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