Elevation changes due to wind

[Jay1]

Question for the F-Class and long range shooters....

 

Do you allow for elevation changes, mid string, in lets say - a fish-tailing wind??

 

Wind blowing from behind you, 4:30-7:30 with velocity changes - up until recently I'd just hold off for wind but I'm thinking I should be holding high or low also in this condition.

 

Without holding high or low is it possible to leek points high or low??

 

Can you quantify the elevation change or just learn this from shooting in varied conditions?

 

Looking forward to hearing your thoughts and opinions on this.

[terryh]

Jay1

 

Not sure on what/how much for F-Class etc. but for larger slow moving bullets there is definitely a noticable effect of cross wind changes on elevation which IMHO are related to Magnus effect. Quantifying this - good luck!

 

Head or tail winds needs someone else to chip in?

 

Terry

[Laurie]

There is a well known relationship in smallbore longer range outdoor shooting with (if I remember correctly) the pattern being high left and low right. There is a formula for 1 click up/down for so many clicks left/right.

 

In F-Class, it's much more about individual range layouts affecting wind and hence bullet movement vertically. Blair Atholl is notorious for this and the electonic scoring monitors often show a distinct impact pattern in some wind conditions at the end of a match with shots blown to the left also high, reverse for right displacement. Diggle also in a valley does it in some conditions. Altcar and Bisley being flat generally no except at Bisley on Stickledown (can't comment on Century) when the wind is from the right especially for the top four or five lanes in the lee of the treeline, the so-called 'Magpie Alley'.

 

Allowance for the effect can be dialled in at Blair, less so at Diggle. The problem is one of consistency - the effect doesn't always apply so you call the wind change correctly throw in a bit of high/low correction too and still lose the point on elevation because the latter didn't show on that occasion for some reason.

 

The other elevation issue is that of the slow steady change throughout a match and keeping on top of it. This can be partly rifle/ammunition related impact slowly changing over the course of 20 shots as the barrel heats / fouls and/or the result of a gradual conditions change. The answer is to plot shots accurately and keep a watchful eye on elevations throughout the match applying corrections as needed. On conventionally marked targets where you can see what's happened to your neighbours on adjacent lanes, it's always worth taking note of the fact that you can see every target near yours being raised with a high or low shot and aiming up or down a bit as appropriate (and keeping fingers crossed it wasn't a 1-minute aberration now gone).

 

The other thing to note here is the increasing use of electronic scales and dispensers like the ChargeMaster which can and often do drift over a loading session. the advice is to place the loaded rounds in the ammo box in the exact sequence that the charges were weighed and also take them out of the box in that order in a match so that if there is any gradual drift it remains just that - sequential and gradual ...... and back to the shot-plot looking for elevation shift trends.

[Jay1]

Thanks for the reply Laurie.

 

What I am finding since I started shooting 215s is that big pick ups / let offs seems to have more of an effect on elevation than the 185s I previously shot, especially in a head / tail wind.

Comparing other target boards in a "condition" everyone got caught in, my round seems to fly a bit higher. I shot alongside a lad shooting 210s and while he got blown up to 11:00 for a "4" just the wrong side of the line mine tends to go a little higher. I finished the string holding high and low "V" but was hoping for a more precise method, eg - average wind speed 15mph, pick up 20mph, let off 10 mph = high / low V or high 5 / low 5. The initial "guess" could see a dropped point or worse.

The majority of people I speak too seem to think any elevations mid string is due to load / bullet and not the wind, but if your load is proven to work surely the elevation element is "out there" and if so, I'd like to be able to quantify it - even if its a rough "guesstimate" its better than nothing.

Your method of keeping / shooting rounds in the sequence they were loaded is a great idea and something I'll be doing from now on.

[Laurie]

Heavy bullets in FTR are notorious for inducing additional elevations, and the heavier the bullet the worse the effect. There has been a lot of discussion on the 215 Hybrid on the AccurateShooter forum and the concensus is that except for a few who practice and practice, it's a step too far with one general exception. The exception is for those who shoot over ranges in the southern US semi-desert states where winds are both strong and which reputedly see switches of magnitudes we can hardly imagine.

 

Most people on this side of the Atlantic who want to shoot anything above the 185gn Juggernaut have gone for compromise chamber throats that allow the 155.5 Berger to shoot well seated shallow and the 210gn Berger LR BT a little deep. They only use the 210 on rough days where the windage gains outweigh the likely elevations' points loss. As always there are exceptions to prove the rule, the main one being the current GB FTR champion Steve Donaldson who after a one season flirtation with the 215 and 230gn Hybrids only shoots the 210gn LR BT, his rifles set up for that bullet.

 

Even the F-Open shooters with a 22lb all-up weight and a more stable front-rest set-up have found the 215 and even more so the 230 hard work in the .300 short magnums and that includes keeping MVs well below what the cartridges will produce.

[Saracen7]

I've had great success with Berger 210 VLD and 215 Hybrids in 300 WM. 

I exclusively use 210 bullets for my hunting.  

215's aren't legal on deer, but aren't sensitive to COAL.  

Both really are wind defying bullets, with massive knock down.  

[Saracen7]

On 05/07/2015 at 12:33 PM, Laurie said:

There is a well known relationship in smallbore longer range outdoor shooting with (if I remember correctly) the pattern being high left and low right. There is a formula for 1 click up/down for so many clicks left/right.

 

In F-Class, it's much more about individual range layouts affecting wind and hence bullet movement vertically. Blair Atholl is notorious for this and the electonic scoring monitors often show a distinct impact pattern in some wind conditions at the end of a match with shots blown to the left also high, reverse for right displacement. Diggle also in a valley does it in some conditions. Altcar and Bisley being flat generally no except at Bisley on Stickledown (can't comment on Century) when the wind is from the right especially for the top four or five lanes in the lee of the treeline, the so-called 'Magpie Alley'.

 

Allowance for the effect can be dialled in at Blair, less so at Diggle. The problem is one of consistency - the effect doesn't always apply so you call the wind change correctly throw in a bit of high/low correction too and still lose the point on elevation because the latter didn't show on that occasion for some reason.

 

The other elevation issue is that of the slow steady change throughout a match and keeping on top of it. This can be partly rifle/ammunition related impact slowly changing over the course of 20 shots as the barrel heats / fouls and/or the result of a gradual conditions change. The answer is to plot shots accurately and keep a watchful eye on elevations throughout the match applying corrections as needed. On conventionally marked targets where you can see what's happened to your neighbours on adjacent lanes, it's always worth taking note of the fact that you can see every target near yours being raised with a high or low shot and aiming up or down a bit as appropriate (and keeping fingers crossed it wasn't a 1-minute aberration now gone).

 

The other thing to note here is the increasing use of electronic scales and dispensers like the ChargeMaster which can and often do drift over a loading session. the advice is to place the loaded rounds in the ammo box in the exact sequence that the charges were weighed and also take them out of the box in that order in a match so that if there is any gradual drift it remains just that - sequential and gradual ...... and back to the shot-plot looking for elevation shift trends.

Century range is terrible for judging wind.  The wind flags may as we not exist, due to the swirling breeze, even at 300 yards. 

High BC bullets really do make a difference.  

[gbal]

Don't forget that a pure horizontal wind (ie no bumps etc) deflects a bullet due to the bullet's  gyroscopic spin. ( Left wind,bullet right and down,Left wind bullet left and up,with the usual right hand twist barrel.)

For a typical 30 cal target bullet,the vertical deflection is  about .035 moa per 1mph wind from 9 or3 oclock.  (And pro rata).That's not much at 100-probably why it's not usually noticed,but it's over an inch down or up-at 300y  per mph,and around 3.5 inches for 10 mph at 1000y.

   Some detail on this ('gyroscopic jump' sort of) was given on Jan 1 in my reply to Hobbit's enquiry, picking up the original OP by Spielvogel pointers July !7 2016,' Which Ballistic App".

Most basic Ballistic App won't handle this ,as it's not the basic three Dof F-(up/side/forward) but derives from the second order (6DoF) parameters-how  the bullet 'wobbles' around these basic three dimensions.

gbal

[terryh]

2 hours ago, gbal said:

Don't forget that a pur horizontal wind (ie no bumps etc) deflects a bullet due to the bullets gyroscopic spin. ( Left wind,bullet right and down,Left wind bullet left and up,with the usual right hand twist.)

For a typical 30 cal target bullet,the vertical deflectionis about .035 moa per 1mph wind from9 or3 oclock.  (And pro rata).Thats not much at 100-probably why it's not usually noticed,but it's over an inch down or up-at 300 (and pro rata) per mph,and around 3.5 inches for 10 mph at 1000y.

   Some detail on this ('gyroscopic jump' sort of) was given on Jan 1 in my reply to Hobbit's enquiry,picking up the original OP by Spielvogel pointers July !7 2016,' Which Ballistic App".

Most basic Ballistic App won't handle this ,as it's not the basic three Dof F-(up/side/forward) but derives from the second order (6DoF) parameters-how  the bullet 'wobbles' around these basic three dimensions,due to wind etc.

gbal

Gbal

Re. Your first paragraph, see my earlier post re Magnus effect ref: https://en.m.wikipedia.org/wiki/Magnus_effect which explains the physics of this.

T

[gbal]

Terry,thanks for this-the Magnus effect is indeed  a 'swerve' effect due to differential pressures from air flow speeds around a spinning ball/bullet. It is not per se a wind effect. It's  essentially how footballers bend their free kicks,or tennis players impart top spin to accelarate  the ball's dropping into court,sooner than  it woud otherwise. I'd imagine the baseball ''slider' delivery is a horizontal version,and no doubt cricket bowlers impart spin to affect the ball's flight.

I was describing something additional,not quite counter intuitive,but not always acknowledged: the vertical displacement component on a spinning bullet that a pure horizontal wind imparts.We are all too familiar with the inescapable horizontal displacement/drift that wind produces,quite a large effect proportional to wind speed and direction(and inversely to the bullet's BC). But the vertical displacement of a pure horizontal wind  on a spinning bullet is not  so well known.It is of course much smaller than the horizontal drift effect,though it differs in that it deflects either up or down,depending on the relation of the bullets spin,to the direction of the wind. An inch at 300y is not  always negligible,yet most ballistic programs can't deal with it-it's not a "3 Degree of Freedom " effect (which they are very good with).A 6 DofF solver is needed,for all these second order 'bullet gyroscopic wobble effects' in the three basic dimensions-up,side,forward...(or just additional scope clicks.) Measurement is difficult,though it is determinate in principle. (Simultaneously fire two identical rifles/loads,but one rifle has right twist,the other left twist,in a cross wind,and measure mean dispersions,compared to either rifle fired alone.Then do the maths-on a big beer mat.    :-)

gbal

 

   

 

[No i deer]

The far right lanes on stickledown are really hard to shoot 1000yds when the wind is blowing .the ground is really undulating a lot this side and the wind plays havoc along there as it swirls or bounces off the trees or both even...! Not sure anybody really knows what its doing

Magpie alley is on short Siberia Laurie.that too is on the far right side.zero 3 lanes to the left then shoot McQueens and your poi has changed....!