Wind Induced Vertical

[Frank Green]

That sketch and how I plotted the dots/impacts....I feel it runs more from like 11 o'clock to the 5 o'clock pattern on the right hand twist barrel but I show it more like from 10 to 4. I don't think it's that’s drastic.

On a left hand twist barrel more like a 1 o'clock to 7 o'clock pattern.

Later, Frank

[Frank Green]

Here is a link to a video that Vortex Optics did at a range that we shoot at close by. The spotting scope and camera where very rigidly mounted so wind wouldn't move the glass around at all.

The video is sped up time wise. I don't remember all the exact details but they started recording around 8 A.M. and stopped recording late in the afternoon.

The range is in Lodi, Wisconsin. This range produces a lot of vertical problems (even on cloudy overcast type days). This range can be so difficult to shoot at that the US team actually took it out of rotation when trying out for the F class and Palma teams if I remember correctly. Which I don't agree with. I feel if you shoot at this range and can to an extent get a feel for what happens there that you can actually learn from it.

The video is titled "Light Refraction, Terrain, Mirage and Moisture"

https://www.youtube.com/watch?v=OBRwQePicpM

Later, Frank

[GSells]

Who was that Plumbs 7 bloke in that old thread “ Vertical dispersion at 600 to 1000 yds “
He’s soooo embarrassing!!

[Barossa_222]

Thanks for the info gents. We were shooting out to 1100 metres on the weekend and the wind was tricky to say the least.

[williada]

Who was that Plumbs 7 bloke in that old thread “ Vertical dispersion at 600 to 1000 yds “
He’s soooo embarrassing!!

It was Plumb Bob, ducking for cover, I think GMan. Have not heard from him for ages. I wonder if he will change his tag and go incognito? Hope not, everyone appreciates his work. Learning is lifelong for everybody. A man that has never made a mistake has learnt nothing.

[GSells]

Who was that Plumbs 7 bloke in that old thread “ Vertical dispersion at 600 to 1000 yds “
He’s soooo embarrassing!!

It was Plumb Bob, ducking for cover, I think GMan. Have not heard from him for ages. I wonder if he will change his tag and go incognito? Hope not, everyone appreciates his work. Learning is lifelong for everybody. A man that has never made a mistake has learnt nothing.

Lol! Nooo , last I heard that Plumbs person after the ET scandal , left for Cuba to pursue a new Plumbing career!! Or was it kazakhstan??? Dunno ! Haven’t heard from him for a while ? Think he still campaignes his lil7/08 ai at times I heard !!

[williada]

Dare I say it, but the centre of pressure is further from the centre of gravity with a longer bullet and gives more leverage to the Magnus force largely responsible for the yaw which is in turn added to by extra drag of the underside on the bullet through the Bernoulli effect which adds to tractorability over long distance by not allowing the nose to dip in line with the trajectory which the centre of gravity follows. Because long nosed bullets want to weather vane the perpendicular horizontal Magnus force, (not the vertical which is insignificant) is also largely responsible for yaw and consequently gyroscopic drift (no wind).

When fishtail conditions exist, in winds above 10 mph, all sorts of interactions of aerodynamic forces exist and lead to bullet instability at long range. This can be seen in the nodal pyramid presented by me in the past, the weathervaning is exacerbated by long bullets.

We also see efforts now in regular conditions at long range (average wind speed 8-12 mph) to optimise things with fractional twists in rifling because long bullets are so tweaky. So what we are talking about is not insignificant. Then if the air density does not match the tune speed stuff happens we don't like.

Further study can show that the Miller stability formula can be improved in long range. A fault may lie with that and other academics because their models are linear models and modern tracking has improved knowledge since. In circa 2002-3 in machine rest testing at 1000 yards, anomalies presented in winds over 10 mph. Now I am more certain as to why.

Minimising extreme spread and positive compensation tunes are not the only reason I have advocated specialist long range rifles in the past. What was deemed to be an accurate rifle 8 years ago to reduce elevation spreads needs further tweaking for set conditions. Bit like golf and a bag of switch barrels or more reasonably, not horses for courses but bullets for courses. Such is life.

A lot can be said for issued ammunition and a level playing field where raw marksmanship prevailed.