How does wind effect elevation

tech24 · Apr 13, 2012

Been shooting xtc for awhile now. I'm not that good yet and my eyes aren't the best so I haven't been accurate enough to learn wind reading well at the 600yd line. I'm starting fclass this year with a hammer of a rig so I think this will help me learn the wind. I understand the basics but I'm unlear on how a head wind or tail wind effects elevation.

I do get it that it you are shooting in a strong cross wind the bullet will be in the air longer so elevation can drop. But does a headwind or tailwind effect elevatio n at 600yds+ enough you have to compensate for it?

If researched a little and found 2 different thoughts on this:

a headwind can raise elevation do to picking up on the bullet or it can lower it do to increase in flight time

Which is correct and is it enough to put me out of the x ring?

Not sure what to think of a tailwind

My goal is a 570 3x600 next weekend at fort hill...hope I can do it.

Thanks for the input!

Leaddog · Apr 14, 2012

The simple answer -

Headwind: lower target impact due to loss of velocity

Tailwind: higher target impact due to less loss of velocity over measured distance

Nanook · Apr 14, 2012

Leaddog: is there a way to quantify how much based on Ballistic Coefficient? And how much would "really" matter?

If it slows down a 77gr SMK to the point it drops it an inch @ 600yds w/ a 30kt 12 o'clock wind (the target carriers are probably F'd at that point anyway), I'm not sweating that at all. That's a 6" X-ring for iron sights, you F-class folks are smaller and may be more concerned.

fa18hooker · Apr 14, 2012

30 knots is somewhere in the neighborhood of 50 feet per second. Supposing that the bullet held the complete and total amount of wind (which it doesn't...it's ability to cut the wind is ballistic coefficient, higher is better), a 50 fps difference is not going to put you out of the ten ring. When coaching pair firing on a team match, the shooter owns elevation, the coach owns (cross)wind. If there are elevation deviations, it's the shooter, and not the wind. If you want a practical application, we're shooting any/any and service rifle 1000 yard on Saturday (the 21st)...come out to the Navy matches and watch Nanook clean house...

Now if you're doing benchrest, and include coriolis effect, drift, gravity, drag, tip-off and the moons lunar phase, you might be able to see a .00001 MOA difference...but I don't hold that hard

tech24 · Apr 14, 2012

thanks for the input it pretty much confirmed my thoughts. For xtc I'm definetly not concerned. For fclass I thought it may be an issue, I'm really thinking not that much though. When I was getting a 600yd zero on my fclass rig I had a wind change about 10-12mph that changed from left to a direct headwind and the RSO said aim high so I did and I missed a clay disc but a few inches high so it got me thinking it can't make that big of differnce. I guess it will be part of the learning experience to figure it out for my rifle and particular range situations. I think light and mirage making my target dance will cause me the most difference with scope shooting. Never had a nice scope or even shot too much with a scope and I'm using a NF and its kinda a catch 22, even at 100yds last week the scope was resolving so much mirage my target was dancing about 3/4", made my 1 hole groups into 1/4 min groups a couple times damnit (it wasn't barrel mirage either).

Mark75H · Apr 14, 2012

There's an ap for that.

tech24 · Apr 14, 2012

Mark75H said:
There's an ap for that.

DAMN IT! Bud light burns the nasal holes...it also makes you laugh more at funny comments on MDS website

E.Shell · Apr 14, 2012

While the "wind under the bullet" crowd busily debates with the "moving box of air" crowd, we watch the terrain.

Flat ground found on most flat ranges does not provide much vertical effect. Hill country or heavy berms will deflect air movement and cause vertical when conditions are right.

tech24 · Apr 14, 2012

I have been awaiting your input, thanks! Looks like shoot and learn type of deal that will vary at different venues. If its like everything else it could differ if I tighten my shoe laces to tight, not shaving before a match, forgetting to go #2 before a match....you get it! LOL

E.Shell · Apr 14, 2012

tech24 said:
...I do get it that it you are shooting in a strong cross wind the bullet will be in the air longer so elevation can drop...

??

Crosswinds do not appreciably affect time of flight. Consider the TINY angle represented by our wind dope and how small a fraction the adjusted departure angle of a few minutes of one degree increases the distance vector. One cannot even click this value on most sights.

Do you mean Magnus?

tech24 · Apr 14, 2012

E.Shell said:
??

Crosswinds do not appreciably affect time of flight. Consider the TINY angle represented by our wind dope and how small a fraction the adjusted departure angle of a few minutes of one degree increases the distance vector. One cannot even click this value on most sights.

Do you mean Magnus?

Well that was coming from some interweb reasearch and nothing I've noticed or applied in shooting with irons. But as I said I'm not accurate enough yet with irons at the 600yd line to really learn or apply too much. I'm glad you have cleared that up and it gives me one less variable to deal with. I didn't think it would make much difference but explaining it the way you did I do see it won't effect much at all. I have never changed an elevation setting during a 20 shot string as long as it seemed to be correct. Another example of incorrect knowledge gained on the web.

I'm not sure what mangus is but will google now.

E.Shell · Apr 14, 2012

tech24 said:
Well that was coming from some interweb reasearch and nothing I've noticed or applied in shooting with irons. But as I said I'm not accurate enough yet with irons at the 600yd line to really learn or apply too much. I'm glad you have cleared that up and it gives me one less variable to deal with. I didn't think it would make much difference but explaining it the way you did I do see it won't effect much at all. I have never changed an elevation setting during a 20 shot string as long as it seemed to be correct. Another example of incorrect knowledge gained on the web.

A hard crosswind wind will render vertical deflection due to the interaction of bullet spin (think "surface wind") with the environmental wind.

Lacking other influences, a low pressure area develops on the downwind side of a projectile, but a combination of a clockwise spin imparted by right hand twist (customary) rifling and a right wind act to move the low pressure area up and to the left, and the bullet moves into this low pressure area.

A left wind will move the bullet right and down.

This effect of bullet spin interaction with crosswinds is referred to as the Magnus Effect.

It is very real and can be documented. Lacking proven data on a given rifle, we start with adding/subtracting elevation equal to about 10-15% of whatever we have to dial on for wind.

tech24 · Apr 14, 2012

Okay, that I do understand, basically. Correcting for it will come with experience I suppose. Darn wind sure is compicated for a beginner. Its gonna be really tough when I start 800, 900, 1000 yd fclass at peacemaker national. Wind is evil there but will be a good learning range. Theres hills and valleys and just crazy terrain. They had their first 1000yd benchrest match and the guys packed up and left and the event calender has been cleared of all benchrest matches.

bbrown · Apr 15, 2012

E.Shell said:
This effect of bullet spin interaction with crosswinds is referred to as the Magnus Effect.

I've read that door gunners have to compensate differently for wind depending on which door they're shooting from. Is that caused by the Magnus effect?

Bryan

E.Shell · Apr 15, 2012

tech24 said:
Okay, that I do understand, basically. Correcting for it will come with experience I suppose. Darn wind sure is compicated for a beginner. Its gonna be really tough when I start 800, 900, 1000 yd fclass at peacemaker national. Wind is evil there but will be a good learning range. Theres hills and valleys and just crazy terrain.

You'll have to pick a prevailing condition, test it with your sighters, then be alert for changes during your group.

Most people use their sighters to find the bullseye and immediately start record fire. This is a tactical error. Use your "unlimited" 800 yard sighters to play with the wind and establish values for more obvious changes you see down range.

They had their first 1000yd benchrest match and the guys packed up and left and the event calender has been cleared of all benchrest matches.

That's just how those BR guys roll. :poke:

bbrown said:
I've read that door gunners have to compensate differently for wind depending on which door they're shooting from. Is that caused by the Magnus effect?

Bryan

Not Magnus, which describes the vertical effect of a crosswind.

Never been a door gunner and I don't know the answer to your question. One of the guys here was though (DorGunR), perhaps he'll chime in. I'd suspect you'd have to lead right when shooting from the right side and lead left when shooting from the left side to compensate for vehicle movement.

tech24 · Apr 15, 2012

Appreciate the tips! I think I get unlimited sighters for midrange this weekend and if its windy I'll do just that and check things out. I like that idea and I was too planning on finding bull and going for score.

How does wind effect elevation

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