new topic, wind effect, why???

S

stiller

Middle aged member
I shot the last PSL at Waco. I observed a very interesting effect to me. Unfortunately, I have been shooting centerfire and this effect will not appear. Here it is:

1. Wind blowing from right to left, flags pointing at between 1 and 2 (headwind) versus 4 and 5 (tailwind). IE same velocity, just a little headwind versus tailwind in a predominately cross wind. Maybe 3 MPH. Tails up about half way or less. Same amount of head versus tail in the 2 conditions.

2. Gun shoots dead center at no condition at all.

With the 4/5 condition the bullet lands a half a hole left and damn near a hole up, basically missing the dot at about 11 oclock. Small angle change and we now have 1/2 condition. Bullet hits same spot left and right, but now same amount low at 7 oclock.

The amount of verticle shown just eludes me. Why is this? Does the roof over the line have much effect at this close of range with this slow bullet? I can see a small amount of vertical with a dominant left-right happening, but this is mostly a vertical effect.

When this condition wig wags back and forth, what do you do? What do you shoot?

Maybe this thread will bring up some good information that is not just theoretical etc and will really help us. (especially me :D)

PS. Similar effects at St Louis, but no so dominant. Partly dont remember what the issues were there and so green may not have noticed small changes.
 
Mr. Stiller,
The why has been beat to death and is in fact of less importance than cause and effect. You have recognized two conditions and learned the effect. Log this info away and when you see the same conditions again you will know how to respond. Prove it on a sighter and take your best shot.

D R
 
Jerry,

The condition you describe and the result would be exactly what I would expect which would be great. It's when it does just the opposite that screws me up. The amount of deflection is due to several things including the bullet speed, the barrel, and actual wind speed. Slower bullets generally buck the wind better. I think the equipment list indicates you were using a polygonal barrel, which is probably why you were simply missing the dot and not going out the top quite a bit assuming you wer not adjusting for the wind. You have to shoot the sighters, determine the deflection, hope they're not lying and to for score.

Fluttering condition would depend on what the sighters were telling me. If they were saying I was generally hitting the dot, I would go for it fast. However, the flutter could fool you and have more push than the other very visible wind. May be better to lay low. If you notice, generally in a flutter, the line gets very quiet.
 
Other than waiting, which is the best idea if you can, at least in centerfire, I have found that shooting heads up, in rapidly alternating conditions, helps with timing a shot. Obviously, this is of little comfort to a bag squeezer.
 
With the 4/5 condition the bullet lands a half a hole left and damn near a hole up, basically missing the dot at about 11 oclock. Small angle change and we now have 1/2 condition. Bullet hits same spot left and right, but now same amount low at 7 oclock.

Jerry,
Sounds like your rifle/ ammo combo is doing what's it should. That 4/5 condition is one of my favorites. On an IR5050 target I'd hold 4-5 oclock on the ten ring and shoot X's. If I had a neutral condition of let up I'd still shoot a ten. I like angles because it drifts bullets less and you can hold closer to center so if you get caught, you still shoot a ten.
If you think about it as the bullet is spinning clockwise in a right hand twist barrel, that headwind from 1/2 is knocking it down and that tailwind is letting the bullet ride up on it. A true 6 oclock tailwind or 12 oclock headwind does little to the bullets path, true being the key word there.
As Wilbur said, when the flags are wobbling back and forth, you're better off to wait it out, if you have the time. Osmetimes you're out of time and just ahve to wing it. Shoot sighers and trust 'em, if if it doesn't make sense bullets are moving the way they are.
Different ranges are different. You don't always get the bullet movement you expect from the wind flag positions you see. Most ranges have bugger winds that you just need to learn and then stay off the trigger when you see that pattern on the flags. That 1/2 pattern you spoke of is one of 'em on most ranges I shoot. Some barrel/ammo combinations will shoot some conditions better than others. You just need to learn what to lay off of, and what to shoot. Everything out there is almost impossible to shoot and score well, and nobody I know does well trying to shoot all the different conditions. Some of 'em wil burn you. It's a patience game.
You're doing ok right from the start. Your scores will come up fast. Those little slow bullets sure doing some crazy stuff.
Patience-patience-patience! I need to write that on my rifle stock! I don't have as much patience as I used to.
 
Came across this the other day. It may be of some use. I believe it is drawn for a right hand twist barrel:

Wind-Rose-2.jpg
 
Jerry, some guys are masters at quickly finding the "prevailing" condition and shooting only in that if it is repeatable. Sometimes you gotta shoot one "point of aim" and one "hold off" condition. Switch winds are murder. More often as not I bet you find with a right twist barrel, you're looking for some version of moderate left wind to go with.
Some guys will only run a few shots on record and then pick around off target until conditions return, some guys know what they want and just wait to shoot until it returns. Every style/twist/# of lands will give you different elevation vs drift variations. We're havin fun now.
P. S. don't forget temp/ air density issues.
 
Some of you . . .

. . . may not have seen my graphic, showing the "Bernoulli Effect".

Bernoulli.jpg
 
Is the Windrose in post 7 correct ? It seems to me that the 1:00 and 2:00 should have a bit lower impact but I am in the same boat as Jerry, ie totally lost centerfire guy.
 
I would say from a theoretical standpoint, the wind rose is correct. From a practical standpoint, I think I would definitely make sure on 1 and 2 and 7 and 8 because 1 and 2 are likely to hit lower and 7 and 8 are likely to hit higher.
 
I assume that the windrose chart is based on poa and poi being dead center in calm conditions. Tell me how do you apply the chart when you have sighted in for a prevailing condition such as 9 or 3. I would now assume that all the reference points on this chart have changed and the only way to know is to go back to the sighters. Also what windspeed is the chart based on. I am fairly new at trying to figure out what the wind flags are saying, and the problem I seem to have most is understanding the slight changes in velocity that are enough to drift the bullet more than I would expect.

Thanks,

Ed
 
crb said:
Is the Windrose in post 7 correct ? It seems to me that the 1:00 and 2:00 should have a bit lower impact but I am in the same boat as Jerry, ie totally lost centerfire guy.
Click to expand...

That particular wind rose is more than a little deceptive for the vertical deflection and would only be correct if the POI for horizontal deflection was moved further from the POA as the vertical deflection rises/lowers.
It also shows an exaggerated angle of deflection of around 45 deg's and the correct angle of deflection for a crosswind is actually closer to 17 deg's (Approximately 9:30 to 3:30) which is an angle based on the calculated crosswind component in conjunction with wind velocity. It's about a 4:1 ratio and means that for every 4 units of horizontal correction....you must add or subtract 1 unit of vertical.

Joe Haller’s chart is much better for a reference but his appears to have the numbers/depictions rounded-off for the sake of simplicity and that’s probably a good idea considering the complexity of the subject.

Another note of interest is that the mechanism which causes this phenomenon is not the Bernoulli or Magnus Effect.

Landy
 
In 99% of the time 1 & 2 will be a little high and 99% of the time 7 & 8 will a little low.
I see nothing wrong with the chart. This assumes right hand twist.
Fred K
 
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