Advanced Marksmanship Heavy crosswind causing elevation change?

[m1match]

Our club's February match was a team match and my partner and I had problems with high elevation misses in a heavy wind. We were both shooting 6.5 Creedmoor with Hornady 140 ELDMs at about 2750 fps. Our barrels were Bartlein 1-8 RH barrels. My scope was a Vortex AMG and his was a S&B 5-25 and we've shot on this range for years with known dope. This match's stages were mostly engaging multiple targets from 475 to 625 yards from barricades and tank traps.

We were both using Kestrel 5700 ABs which give us reliable solutions every other time we've shot, and which matches our logbook data. The winds we usually shoot in are 3-8 mph left to right.

The wind this day was much heavier than normal for us. It was from 20 to 35 mph from 1 o'clock to 2 o'clock and we were missing high .2 to .3 mils consistently. Only when we brought our elevation down .2 to .3 mils lower than our Kestrel predicted elevation and our logged data did we get back to hits.

I've never seen this before in all the years I've been shooting long range which is a lot of years. I also have never shot a match in winds this heavy. Our RO's Hensoldt spotter on a Feisol 3372 tripod with a weight hung from the RRS leveling base got blown over, it landed on the eyepiece but fortunately the rubber eyecup kept the eyepiece from being destroyed. Doing a web search yielded some articles on aerodynamic jump causing elevation changes, but .3 mils at 500 yards????

I'd like to hear of other's experience, I'd like to better understand what happened.

 

[morganlamprecht]

If u were using your kestrel to capture direction of fire and direction of wind it factors in their formula for AJ automatically, unless u manually set wind speed 1 to 0...I think it’s about .1 for every 5-10 mph or so...I’d have to check, I don’t use it tho, never seen the need to

 

[alpine44]

Aerodynamic jump is part of what you observed but unless the terrain is as flat as a football field, there will be up and downdrafts in any wind. This affects the bullet just as a crosswind does.
Too many people believe these days that a Kestrel somehow turns a rifle into a guided missile launcher.

 

[m1match]

I was not using the direction of fire and direction of wind function in my kestrel and our range is at the base of a steep hill and slopes up from the firing line about 8 degrees. I’m guessing usually the wind isn’t strong enough in our normal conditions to cause terrain or aerodynamic jump to be enough of an influence

 

[Diver160651]

Last match out wind ran up to 25. The only stages I had left to shot max’d around 745.. no issue with elevation.

I’ve shot a lot of matches in similar winds. I have not seen enough change to make an elevation miss on a steel plate @ 500

All that said, when the wind is rocking so does our bodies and supports/barricades, even the rifle barrel can shake when prone - that can be very problematic.

 

[m1match]

That is true, the stages that I was having problems with were tripod and barricade stages and the wind was playing havoc with our body stability.

 

[isofahunter]

right to left wind impact up left to right impact down.

 

[Diver160651]

Just to clarify - yes 25mph wind can make a couple of 1/10s at 500; but your targets are centered up.. I image they are about 2moa/.6 mils+ if your missing by another .3 mils.. that’s at least .6mils; too much for wind alone. Hope that makes sense .

 

[m1match]

Thank you for your input, I would probably conclude that the wind which was right to left would account for part of the elevation change but the rest was probably me, my position, and the instability caused by high winds.

 

[Tiger_Shilone]

Magnus effect. Well known in the bench rest circles. This article describes it as "bournelli effect", but it is really magnus and the picture is accurate as to what bullet path changes happen http://www.thewindisnotyourfriend.com/read/bernoulli.html

Youtube has some good vids, this is pretty interesting

 

[Gunfighter14e2]

The river of wind is never constant nor traveling in the same place all the time. Depending where the river hits the projo in flight will dictate where the projo impacts the target. This is but one reason to never chase your last shot, at times.

 

[Lowlight]

It happened at Pawnee this weekend, we had 30MPH winds, and I saw it with my loads.

I was going very slow with a Tikka Tac A1, shooting factory Prime 130s at only 2750fps,

My verticals were all over even at shorter ranges. Mostly tossed them down as the wind was from the left.

Now other guys were shooting faster did not see it as bad, but with my slower velocity, I saw it.

I averaged about .3 off vertically

 

[Diver160651]

It happened at Pawnee this weekend, we had 30MPH winds, and I saw it with my loads.

I was going very slow with a Tikka Tac A1, shooting factory Prime 130s at only 2750fps,

My verticals were all over even at shorter ranges. Mostly tossed them down as the wind was from the left.

Now other guys were shooting faster did not see it as bad, but with my slower velocity, I saw it.

I averaged about .3 off vertically

Yes.. BUT not enough to MISS by .3 mils at 500 like the OP was asking.. Thats on average a .6mil change need on a 2MOA plate, and some of these plates are larger.

I know this is going to sound weird to some shooters.. especially those that have not routinely shot positional in winds that leave you with burning lips, or that will actually blow a rifle off its BIPOD if left untended. Antidotal as this may be, it seems no mater what crossing direction the wind is blowing people start to miss higher on average, even if it is also in their left and right miss.

We must remember that on average the plates are larger even when centered up than these ripping cross winds should move the POI - UP or Down. Now I am not saying, that the "effects" are not true - but it may be overstated a bit like SD and often the wind itself in some solvers, but mostly shooters. Again, as an example my 500y dope might be U2.4mils. If I sale .3 mils above a 2MOA/.6mil target (many in positional are much larger) .. No way, is my real dope (due to even a 25 mph wind) actually 1.8mils. ( a slow 308 might be a couple of clicks but not .6+)

What @m1match described, the tripods blowing over or the barricades moving like crazy, or just our bodies blowing around make shooting unstable. I think when most of us are in that situation we tend to get very sharp and quick on the trigger, maybe it is something else, a lot of seem to do something weird, because the elevation starts looking a bit better if the next stage has a prone element. If I slow down to brake the shot as cleanly and smoothly as I can with good follow-through and do not worry about time in these conditions, some of that goes away.

 

[Lowlight]

I saw it in the prone with a solid position, the wind had nothing to do with me missing low in the prone.

the positional was definitely the wind, we had an 85-yard shot, and I just clipped it, lateral, no drop issue. That was off a tripod it blew me sideways.

The prone stuff, verticals showed up and I think ti was MV related as the guys going over 2900fps were not seeing issues, I was only at 2750fps with a 130s

I was .3 off at 200 yards ...

 

[Lowlight]

At 500 yards, I dropped a full 10" plate low too, I was hitting, hitting, my 3rd shot, dropped a full plate low at this distance with a 260

 

[Diver160651]

I saw it in the prone with a solid position, the wind had nothing to do with me missing low in the prone.

the positional was definitely the wind, we had an 85-yard shot, and I just clipped it, lateral, no drop issue. That was off a tripod it blew me sideways.

The prone stuff, verticals showed up and I think ti was MV related as the guys going over 2900fps were not seeing issues, I was only at 2750fps with a 130s

I was .3 off at 200 yards ...

Well maybe this is something to get more people documenting just like The CE and SD thing.

But again, Like you guys, we shoot a ton in the hills and wind. Yes, 3150 helps.. But the guys that are the calmest seem to smoke the others in this type of conditions.

What I see, is not just left right shake in the scope but BOUNCING L&R and U&D due to even the barrel in the wind. If it was just bournelli, we'd all dial it in and be done.

How much wind does your trusted solver predicate with a 30 mile cross wind predict with a 140 @ 500? Maybe .3? How does that turn to 2x that? Maybe, I am not seeing it as much because of my speed,

I am listening not arguing..

 

[Lowlight]

The solver and I'm sure the BC was off because the data was not perfect this time out, the wind at 500 was calling for 2.5. I trued the velocity to match at 24.5 MPH in Coldbore. Most solvers were giving a .1 change in elevation, and that was not enough. .3 was a pretty consistent correction.

I know I was good left to right wind wise, where I missed was low in most of these cases. So my hold was centered, but my vertical dropped low.

I really think it was a speed issue, normally, the worst I shoot the 130s is 2875, most of the time it was over 2900fps, here at 2750 it was not responding. I think there was a cascading negative effect going that slow in these conditions.

I did not see it happening with guys over 2900fps even in the 6CM, I know Mike used 1.1 Mils of wind on the same target I was using 1.8 to 2.2 depending on the gusts.

 

[isofahunter]

Wind is a fickle bitch. I too think MV is the big factor in this based on what I have seen.

 

[Diver160651]

The solver and I'm sure the BC was off because the data was not perfect this time out, the wind at 500 was calling for 2.5. I trued the velocity to match at 24.5 MPH in Coldbore. Most solvers were giving a .1 change in elevation, and that was not enough. .3 was a pretty consistent correction.

I absolutely agree with .1-.3 depending on speed. You may have missed the original post was .3 over a 500y yard target. So thats like .6 or more away from the center. That is what I was trying to explain.

 

[Lowlight]

that one round at 500 went that much low and more.

I really think the speed is a huge factor here, at 500 I know I dropped double the size of the target low. At 200 I was .3 low, had .3 dialed on, and had to double it to .6 to hit the target.

The farther out the worse it got and not on every shot because the gusts were so bad. if I caught the gust wrong it doubled the drop. The solver changes were wrong, the actual hits needed double in a lot of cases

 

[morganlamprecht]

has anyone gone out on a large flat piece of land and locked a rifle on a 500 yd (or whatever) target and shot with a 15+ mph L-R wind and then spun the rifle around and locked it on another 500 yd target and shot it with the R-L wind to see the difference?

 

[Lowlight]

I would try it, but I need to the wind to face a specific way. My normal wind is L to R from my firing line if it's a headwind (which does happen) I can do it, as the range layout will work, but the way my range is right now, I can't with my typical winds. I'd be shooting towards the road.

 

[morganlamprecht]

it would be nice to see...i dont have anywhere set up to try it out...anywhere i could set up to shoot both directions has so many trees/brush that it would be most likely wind blocked going 1 way or the other

 

[Diver160651]

I would try it, but I need to the wind to face a specific way. My normal wind is L to R from my firing line if it's a headwind (which does happen) I can do it, as the range layout will work, but the way my range is right now, I can't with my typical winds. I'd be shooting towards the road.

Frank how did the winner of you match account of the wind? How much elevation did they run? I am not suggesting for one minute that your info isn't correct, just like to see the difference in speed and corrections.

The windy season is usually May thru summer for us. I don't have a bench rest, but can try reversing DOF shooting prone during that time.

Here is a couple of observations that I don't know how to account for, but maybe a good conversation for your podcast.

1. Is it projectile dependent results, not just speed? Just as an example: With the ELR stuff I have seen things like the Amax, with 5-6 mils of wind run relatively true elevation wise around 1/2mil to no windy days, but super high BC bullets running slight faster in the same rifle get jacked by the wind with elevation all over the map to the point of being not even fun. . (guessing that is some sort of wind induced instability).

2. It is still hard for me to discount the fact that even in high L-R winds, shooting off wonky items, I see a lot of elevation misses high, sure some low, but why any high? Again, I think a lot of what we are seeing is additional shooter in that circular wind bounce.

3. I think we need to discount match conditions because a lot is going on. I personally have not seen +/-.6mils of wind elevation correction inside 500 or anywhere close in that 20-25 winds that we can get. I think a lot of people might not know how windy 25 is when on a rifle, just holding the rifle.

 

[morganlamprecht]

3. I think we need to discount match conditions because a lot is going on. I personally have not seen +/-.6mils of wind elevation correction inside 500 or anywhere close in that 20-25 winds that we can get. I think a lot of people might not know how windy 25 is when on a rifle, just holding the rifle.

ive seen a TON of these, and even had a few myself...as i tried to track them down after the fact, it ended up being shooter error or equipment issue, but ive never had anything show consistent results

 

[Diver160651]

@Lowlight

I’m three minutes 18 seconds into episode 30!

This one is starting out great. Let me revise my above post to say, since Mike won let’s have tell us what he did

 

[Lowlight]

I don't think Mike did anything different, he was in my squad and was shooting a 6CM. H never mentioned adjusting his dope. I knew where it as me, I was moving in the various positions but my prone was solid. I was on a concrete slab, no rush the time limits are super generous, and all felt great.

As Morgan said, it's random and not on every stage or distance, but I did see it happen more than once. I chalked it up to catching the gusts the wrong way, as the range there in Pawnee is pretty flat, there is not a lot of terrain to get in the way.

Because I started off on the short side, no range was over 305 yards in this segment, but the targets are like 1 MOA or smaller, it was easy to see the elevation differences. Having to add .3 at 200 is basically doubling the dope. The computer said .3 I used .6 to hit.

The Long Range / KD section has you shooting multiple targets, many 2 MOA or bigger, but they also shrink to smaller. ( the 820-yard target is 4" ) What I saw was, the 2 MOA targets I hit, as they shrunk in size I could see where the elevation was off. These targets also have a berm behind it so you can see your misses. So once the targets got small enough I could see it drop low. The 500-yard target both me and the Spotter were like WTF when it dropped so low. it could have easily been a bad round. But when you are shooting 5 shots, and you start off hitting, 1, then 2, then 3 drops a full plate low, and 4, drops 1/4 plate low and 5 drops just off the plate low you have to wonder.

The rifle was not really up to snuff and I wonder if it was a combination of the slow speed with the high wind. I did not see it with the faster rifles. Like I said I feel the rifles shooting 2900fps or faster were not experiencing it. I really think we are much more speed dependent than we give it credit it for.

 

[m1match]

What Frank saw is similar to what I was experiencing in my original post. We were engaging small targets, like around .3 to .4 mils in diameter, so my misses were .2 to .3 mils high at 507 yards, which was .4 to .5 mils above target center. The wind was right to left which we would expect to raise a bullet out of a RH twist barrel, whereas Franks wind was left to right and was causing his impacts to go lower than predicted. Same with the gusts, if I shot during a gust I missed whereas I feel I caught it in a lull I didn’t miss.

 

[Diver160651]

I just listened to Frank’s podcast. Well actually before I walked into a meeting. I’m driving now and replying via Siri.

I loved the podcast/

Anyway, maybe Frank had a lot more going on than just the wind bullet interface. Maybe his system was vibrating lot more than realized.

I also assumed that you guys both were shooting what you normally see running 2moa or better.

I am shooting faster than you guys, but feel a lot of my misses in elevation that out strip the solver in high wind are to the buffeting. If I shoot on my RRS/leveling head the groups open vertically but way the hell less than if I try to use my lighter Ferisol and ball head.

On some barricades there is so much wobble with the wind I don’t know how we decide how much of the vertical miss is wind and how much is shooter.

The other interesting thing is that two guys shooting nearly the same system in high winds one guy has a bunch of vertical in the misses and the other doesn’t.

I’m not saying I have the answers, maybe they’re just missed placed observations. But I’m eagerly awaiting podcast 31

 

[Lowlight]

I am only considering what I saw in the Prone ... not any of the positional or Tripod Stuff

Even the misses on the 305 & 200-yard targets were from the prone and not from a tripod.

I did mention some tripod stuff, and other things, but as noted in the podcast I did not even shoot the other stages that included the barricade. Mainly because my verticals were not lining up at all. I felt it was not worth trying to adjust on the fly anymore because what I saw prone was not helping.

Being .3 off at 200 is a lot to me when the dope at 200 is between .3 and .5 at the worst, going to .6 pointed to an issue. Then the KD area was also prone from a concrete pad, just about admin conditions as the clock barely mattered. Same random low hits. I started much of that area hitting the bigger targets and then dropping wildly low in the gusts.

 

[Diver160651]

I am only considering what I saw in the Prone ... not any of the positional or Tripod Stuff

Even the misses on the 305 & 200-yard targets were from the prone and not from a tripod.

I did mention some tripod stuff, and other things, but as noted in the podcast I did not even shoot the other stages that included the barricade. Mainly because my verticals were not lining up at all. I felt it was not worth trying to adjust on the fly anymore because what I saw prone was not helping.

Being .3 off at 200 is a lot to me when the dope at 200 is between .3 and .5 at the worst, going to .6 pointed to an issue. Then the KD area was also prone from a concrete pad, just about admin conditions as the clock barely mattered. Same random low hits. I started much of that area hitting the bigger targets and then dropping wildly low in the gusts.

Well this is what makes the hide assume again.

While I have shot a bunch in that 20-25 not so much in that 30-35 and I am shooting almost everything I shoot faster, maybe I am on the good side of the hump. Getting .6 or more so close, is something I have not seen from a solid load and position. So I love to learn what is happening and where that Speed/BC line is where all hell brakes loose.

Anyway, thanks for being back the site.

Btw and off topic- What happened to the operator video you did, with a head on a swivel? It was priceless.

 

[Lowlight]

Youtube

 

[Diver160651]

Youtube

Thank you! Made my day. I’ve been wanting to send this to a buddy for a while..

 

[MakeSawdust]

I agree with reubenski. That rule of thumb has usually worked well for me. I also have been shooting DTACs out of a 1:8 Criterion at about 1000' ASL. When it is cold they are not stable, and in high pressure situations in mild temperatures they are only marginally stable. At 70 degrees they shoot really well. When I play with the Boatright and Ruiz cwj calculator, the more stable the DTACs are the less cwj the model predicts. This could also have something to do with faster velocities seeing less effect. The model seems to be correct when shooting, but if you figure in all the small variables such as a slight zero offset, the effect of lighting conditions, and mirage it is hard to be sure. As has been said the test needs to be identical rifles and loads shot in opposite directions simultaneously. I think I remember a video where David Tubb and a friend are doing that while showcasing his DTR reticle. This is certainly an interesting phenomenon to try to pin down accurately. The more I see people talk about it the more questions and less answers I have.

 

[Mordamer]

I shot a club match a month ago with 25-35 mph cross wind left to right all day long. Most of the day I had 28 MPH entered into Strelok to get hits. This match went out to 730 yards. I didn't have trouble with elevation all day. I hit close to 80% using 130 ELD-M's at 2,900 FPS. This range was over very uneven ground with several valley's between targets and shooters. Maybe the circumstances have to be just right to get that large aerodynamic jump.

 

[hic28]

@op - do you shoot our match every month? If so I’ll explain in person.

For everyone else, this is the range the OP is talking about for reference

The location of the targets that everyone almost always shoots over are just at the tip of my barrel, going up the right side of the range up to the miners road (cut in the hillside)

On the right side of the road up the hill, there is a small valley and creates a Venturi effect with the much more turbulent air than the center of the range. That along with a south facing hill the temps heat up pretty quickly and now you have rising heat. If you watch the socks on the left side of the range and the right side at the same distance you’ll see 2 different indicated speeds (this is where I theorize the Venturi comes into play)

It’s hard to tell from photos or even from the firing line but taking a trip to the 700 yard line it becomes very apparent that the hill is rolling away from the firing line as you move to the far right targets.

I recommend to everyone who shoots our matches to take an aviation weather class to understand in more detail how air flows over and around hills.

 

[Deleted member 10043]

I had to a 20% vertical deflection of crosswind wind not too long ago shooting 260 loaded at factory type speed. It was 1.5 moa silhouettes out to 500 meters. But the range or or angle to the target didn't matter. Bullets were 136.

 

[j-huskey]

USAMTU, (AMU), and SOTIC documented elevation differences in crosswinds several years back. It's a known in certain circles .
The 118sb was predictable given the specific barrels in use at the time.
The elevation changes were different depending on where the wind in the arc intersected the bullet . Up arc, impact up, down arc, impact down.
The anomoly exception to that was in the rotation direction, the depth of engraving, and the direction of the wind.
The rougher the jacket engraving, the greater the effect.
Sabot rounds with no engraving had the least effect.
And no, I no longer have the reference materials or access to them. The testers are mostly dead now.

Higher bc, faster, less engraved bullets are less affected. You probably can program your "predicter" with known data and beat this phenomenon.
It's been done firing ship to shore to some degree b4. Some of the ballistic programs in use today used shipboard data in their creation.

I remember those hide discussions with Blaine Fields and Gustavo... waaaayyy back when.

 

[Deleted member 10043]

All I know is what the bullets were doing that day. Wind was about 15 full value from 9:00 and pushing elevation down .2 mils. First two or three targets on each relay was a low miss or hit in the base. Came up .2 and back on target for the rest. After the first relay was out of the scoring so I repeated each remaining relay just to confirm.

 

[m1match]

hic28 I'll be there this month and look forward to seeing you.

 

[Graywolf.260]

Where I have been shooting the past couple months in N central MT the wind is nearly always from the W, typically ~10 mph in the evening. Two days ago it was unusual, from the E at 5. I was scratching my head seeing hits at 1100 yds (target to the north) were .2 mil high that evening fwiw. 260 rem 2790 fps, Berger 140 VLDs. I'll see if it comes back down when the normal wind pattern returns.