Vertical dispersion at 600 yds to 1000 yds

[plumbs7]

Well we have had 2 really great threads on sd and extreme spreads! I thought I would bite my tongue on future topics ! However at the risk of being shot down by keyboard shooters . The benefits far outweigh the negatives!

So another phenomenon to consider! As in Alan's graph why do f standard .308's seem to do better at 1000 yds !

Does frontal and tail winds affect vertical from 1000 yds to 600 yds ?

This is where a Saum may come into its own by having a shorter time of flight!!??

[mike H]

Well we have had 2 really great threads on sd and extreme spreads! I thought I would bite my tongue on future topics ! However at the risk of being shot down by keyboard shooters . The benefits far outweigh the negatives!

So another phenomenon to consider! As in Alan's graph why do f standard .308's seem to do better at 1000 yds !

Does frontal and tail winds affect vertical from 1000 yds to 600 yds ?

This is where a Saum may come into its own by having a shorter time of flight!!??

Plumbs,
Probably I may be one of these keyboard shooters,just ignore me,I am following all this on SD and extreme spread,with great interest also.
Mike.

[plumbs7]

Well we have had 2 really great threads on sd and extreme spreads! I thought I would bite my tongue on future topics ! However at the risk of being shot down by keyboard shooters . The benefits far outweigh the negatives!

So another phenomenon to consider! As in Alan's graph why do f standard .308's seem to do better at 1000 yds !

Does frontal and tail winds affect vertical from 1000 yds to 600 yds ?

This is where a Saum may come into its own by having a shorter time of flight!!??

Plumbs,
Probably I may be one of these keyboard shooters,just ignore me,I am following all this on SD and extreme spread,with great interest also.
Mike.

Thanks Mike for your kind words!

Im not going into what happened at a Trianing session that has caused all of this sd and extreme spread. And now frontal winds !

Look I have found from ( I'll stick my neck out again) my own experience when the wind is in my face I've experienced vertical and same with tail winds !

I remember with last years Qld Queens I think it was . People complaining of vertical at Belmont at the longs. With one person saying"I didn't have any vertical! But I just didn't shoot with the wind in my
face !"
So is there anything to this or is it sd and ex spread?
Regards Graham.

[DenisA]

I'll add some of what I've experienced.

With all bullets, but worse with bullets like VLD's and especially hybrids where the shank is short and the ogive is long, the centre of pressure is further forward of the centre of mass, they are trying harder to tumble which I believe results in yaw. There are different levels of yaw I guess, from properly balanced, light to extreme which would be evident straight away. I think this is where many of us come unstuck.

In developing a load in good conditions a bullet that's yawing lightly can still produce good groups at the shorts and a good score at range which can give us a false sense of security in the load. But when the poor conditions pick up, especially head winds they are more susceptible to yawing out of control faster than the same bullet that is better balanced in a more ideal set-up. Obviously there are many things that the ideal setup umbrellas.

I remember shooting in terrible conditions at Belmont one year, maybe 600y. I'd walked the line and seen a few 51's. Cam Mc was next to me and we started the shoot at the same time. My .284W was running really well. I went straight in to damage control mode rather than X mode and I worked hard, didn't rush and I dropped I think 6 points. I was really happy with that because they were the conditions that you know everyone is going to be getting smashed in. I got up smiling quite happy and looked up to see Cam check scoring already. I smiled at him and said "That was hard", looked at his score of 60.? and then realised how much of a dick I was.

Currently I'm shooting a .300wsm and 185Jug's. It's still early stages, but so far it's proven itself to be very competitive. Last weekend I ran it through it's first PM. 60.7 at 300y, 60.6 at 500y and at 900y the vertical was sensational in terribly volatile and strong conditions. I won 900y against some very slick 6.5mm and 7mm F-Open bullets. I ended up with the highest X count for the weekend. I dropped behind the front runners at shorter ranges, in brilliant conditions of day 1 and gained points back on them in poor conditions at the longer ranges of day 2.
The 185's don't have the BC that the others have but the tangent bullet puts the centre of pressure closer to the centre of mass with a longer shank and shorter ogive. They're easy to tune, easy to balance and consistent. I believe they are far less inlined to yaw. The good vertical at the longs may also have a lot to do with the additional radial torque that a .30cal has over lesser diameter bullets, as Williada has mentioned in the past.

I think that because 30cals are wider, they're generally shorter which makes them easier to balance. That's is except for the long ones such as the 215's and 230 hybrids which I tried to get shooting well at the longs for a long time unsuccessfully. Very tight groups at 100y though. I think they really need an IDEAL setup and are less inclined to shoot in the regular rifle .30 cal barrel configurations we see.

Probably nothing here to help you out, but relevant to your topic none the less.

[KHGS]

Well we have had 2 really great threads on sd and extreme spreads! I thought I would bite my tongue on future topics ! However at the risk of being shot down by keyboard shooters . The benefits far outweigh the negatives!

So another phenomenon to consider! As in Alan's graph why do f standard .308's seem to do better at 1000 yds !

Does frontal and tail winds affect vertical from 1000 yds to 600 yds ?

This is where a Saum may come into its own by having a shorter time of flight!!??

Do they really????
Keith H.

[plumbs7]

Keith yep I sort of agree ! My 308 always did better at 100 m lol! But what I was goin about was what Denis was talking about with .308 able to be better stabilised with radial torque in head/tail winds and wind shier! There maybe something in it ! ??

Jandowae last year at 900 yds there was a stiff tail wind that would be there ten would come from 9:00 o clock and with 180 hybreds I would be in the centre then wind behind at the top of the 5 ring nearly a 4 ! I aimed opposite in the same conditions while it was a round and was back in the 6/x ring again!
That was my first real experience with that kind of vertical!

Bryan Litz says in one of his books Frontal and head winds have little or no effect on our bullets !

I would beg to differ!


At last Nats I was at ! It was 800 yds and an ftr shooter was doing really well on their string ! Then the wind rushed into our faces and I was thinking" don't pull,don't pull the trigger ! Bang! "
A 4 came up at 6 o clock! Their has to be something in it as I've seen it time and time again !
[URL=http://s1304.photobucket.com/user/Plumbs7/media/Mobile%20Uploads/1B357B91-95FD-4960-A18B-C2042DA32F54_zpsriu7f1th.jpg.html][/URL
I'll bring up my test target at nearly 500 m !the 3 high shots and remember I did this blind and shot straight after shot!
The 3 high shots the wind did rush up behind me and we have to bullets through the same hole ! So has to be conditions! The chrony data would have to be I think it was 60 fps faster to drop out the top at one full 1/2Moa high!??? It wasn't ! Maybe I pulled the shot ? Yep maybe ? But 2 shots through the same hole !?? I am banking on conditions!

What's other people's thoughts?
Regards Graham

[jasmay]

Litz says that? I'd like to read that, I don't remember ever reading anything tk that effect in his books.

[plumbs7]

Yep I believe so in his " applied ballistics for long range shooting " I did read it in there ! But to be fair am opperating of my memory on that one! I could find it if you want to push the issue but maybe a waste of time ! Maybe someone with more time than me could find it if they really wanted to ! It was near the middle of the book near the photos of him shooting at a range in the snow with a .284 from memory !

[jasmay]

Graham, I'd love to see it, I think you have misinterpreted what ever it is you read.

In laymans terms I describe it like this.

Head or tail winds effect elevation in the same sense that distance does imagine perfect zero wind condition @ 1000yds your dope will be spot on, now lets say we add a head wind, effectively making the bullet travel further in the wind, what will happen?

Now 180° the wind so its over your shoulder, effectively carrying the bullet or making it fly through less wind what will happen?

This is simple, plain, dumb terms there is much more going on I don't care to explain as i'm not well versed in explaining it, but that is how I look at head and tail winds and their effect on elevation.

Get out and throw a paper aeroplane into and with the wind, what happens.......

Someone tell me I'm an idiot, please....

[Norm]

This is my take on it for what it is worth.

That TMT wind vector chart is BS in my opinion.
Points 6 and 7 are far too different for such a small change in wind direction.
Any wind will have a vertical component particular to the topography that the wind flows over and any eddy currents about due to trees etc. These can be random or constant depending on the range topography and weather conditions.
The vertical component can easily be 20% or more of the horizontal component. Especially with mild winds. This can change rapidly from a positive effect to a negative effect from one shot to the next.
If you have 3 moa of wind dialled in and are getting 1 moa or more of vertical dispersion, I see nothing strange about that. Especially over slightly undulating ground typical of a lot of rifle ranges.
Shoot one of the big guns over long distance across hilly terrain and you can see far more variation even though they have projectiles with super high BC. Switch to a smaller calibre with lower BC and the magnitude is greater but of similar direction.

I have practice locations that I have got to know very well and the vertical differences that I get are very predictable for a given wind direction and strength. Those that shoot on their home range have an advantage in knowing what wind will produce vertical issues on their range and how best to deal with it.

[plumbs7]

Jason I think that's perfect dumbing down of what happens ! I agree with you ! It stacks up to what I've experienced ! Also like Norm said topography can also play a part too! Bullets will drift up or down with the same amount of drift as horizontal drift according to their BC!

Now Mr Litz said pg 117 bottom paragraph " the wind was quite steady at 8 mph directly from 6 o'clock.
Of course wind conditions are never precisely consistent for a group of shots .
Fortunately for this experiment, head and tail winds have a relatively minor effect on bullet drop. The 8 mph tail wind only lifts the vertical impact of the bulletby less than 2"at 991 yards! "

I've experienced a lot more vertical than that! So there's more too it ! Ignore head and tail winds at ur peril!

[KHGS]

Keith yep I sort of agree ! My 308 always did better at 100 m lol! But what I was goin about was what Denis was talking about with .308 able to be better stabilised with radial torque in head/tail winds and wind shier! There maybe something in it ! ??

Jandowae last year at 900 yds there was a stiff tail wind that would be there ten would come from 9:00 o clock and with 180 hybreds I would be in the centre then wind behind at the top of the 5 ring nearly a 4 ! I aimed opposite in the same conditions while it was a round and was back in the 6/x ring again!
That was my first real experience with that kind of vertical!

Bryan Litz says in one of his books Frontal and head winds have little or no effect on our bullets !

I would beg to differ!


At last Nats I was at ! It was 800 yds and an ftr shooter was doing really well on their string ! Then the wind rushed into our faces and I was thinking" don't pull,don't pull the trigger ! Bang! "
A 4 came up at 6 o clock! Their has to be something in it as I've seen it time and time again !
[URL=http://s1304.photobucket.com/user/Plumbs7/media/Mobile%20Uploads/1B357B91-95FD-4960-A18B-C2042DA32F54_zpsriu7f1th.jpg.html][/URL
I'll bring up my test target at nearly 500 m !the 3 high shots and remember I did this blind and shot straight after shot!
The 3 high shots the wind did rush up behind me and we have to bullets through the same hole ! So has to be conditions! The chrony data would have to be I think it was 100 fps faster to drop out the top at one full Moa high!??? It wasn't ! Maybe I pulled the shot ? Yep maybe ? But 2 shots through the same hole !?? I am banking on conditions!

What's other people's thoughts?
Regards Graham

Hmmm pretty pics, but in my opinion 308 is still marginal in comparison to 7mm's with 180 grn bullets at 2850fps or 168's at 2950fps or even 175's at 2900fps at 1000 yds, assuming we are talking about the F-Class disciplines. we have touched on a couple of aspects in this thread which are off topic so I won't comment on them here. But I will say that often what actually happens in practice can be at odds with the numbers & this kinda messes up the picture somewhat. I am not eloquent enough to put my experiences & thoughts down in print, but I have found many instances that conflict with the "numbers", maybe they were "flukes" I don't know, however I am certainly not suggesting that our learned contributors are wrong with the "numbers" just that I have seen many contradictions in my "unscientific" testing over years past. In regard to head & tail winds my findings tend to agree with Brian Litz.
Keith H.

[Nathan P]

My experiences for what it's worth

I've found about half a minute worth of elevation shift when the wind is switching between 3 and 6 o'clock,
Obvioulsy a head wind will push you down because the bullet is being slowed down by the wind and the reverse for a tail wind which is fine as long as it stays constant but for those of you that have shot at Campbell town would know does not happen very often, in those situations I just try to find a flag I can look down the guts of to keep an eye on that small shift in direction

[Razer]

For what it is worth!
Here are a couple of websites that deal with the basics of wind, and, in the rifleshootermag article, which is taken from the Ultimate Sniper, it says that frontal and rear winds do not affect elevation.
Quote:(as link may not load).

By Maj. John Plaster
In order to interpret and apply wind compensation correctly, you have to determine the angle of the wind; how it flows across the bullet will determine the amount of drift. A tail wind or head wind will have no value; they have essentially no effect on a bullet’s flight. A direct crosswind, which blows from 90 degrees into the path of the bullet, is called a “full” wind because the full effect of the wind is experienced.

Read more: http://www.rifleshootermag.com/shooting ... z4Az5u1Y2d


My personal opinion is that the biggest factor in elevation changes at longer distances is whether the wind is coming from the left or right. On a perfect day, you can( or should) hit the X ring centre if your gear and position are all in sync. When the wind changes your elevation will move according to which side it is coming from as Nathan has pointed out.
Air density has a fair amount of affect also as this will alter the time to target which must affect elevation, so cold days give a different value to hot days assuming your ammo temps are the same.

The websites are probably not much help, but left and right wind elevation changes were hammered into us as a basic instruction in TR many years ago.

https://docs.google.com/document/d/1SXs ... /mobilebas

[Malcolm Hill]

For what it is worth my opinion of the vertical issues at Belmont with a frontal wind are quite easily explained. Due to the height of the mounds on that range between the muzzle and the 1000 yard targets it it is wind rising and sinking and the up /down movement of air that the bullets must travel through causing the issue. If it were possible to graph the air pressures and densities above the mounds in the bullets path I'm sure many would be surprised at what happens. For anyone familiar with light aircraft travel around and over hills and mountains they would know that most times there is noticeable unstable air above them even when you are quite a height above. At Belmont when the wind is from the left or right travelling parallel with the mounds vertical issues don't seem to arise but as soon as the breeze comes in to your face and rolls up and down over the mounds the bullets get lifted and dropped over each mound on their way to the target. The are a few other ranges around where this also happens and sometimes due to the layout of the mounds or it can be just one mound it can effect one side of the range and not the other. I bet if plumbs7 had his Yak do a low level pass over those mounds with a frontal wind he would have a hell of a time trying to hold a steady elevation. Regards Malcolm.