Yes it is, just reverse for left twist. Didn't realize the chart would cause a stir.
Speedys magnus effect chart
- Thread starter clean hands
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With my faulty - OLD - memory, and not being a rocket scientist, precession may be an incorrect terminology, however, the bullets is a gyro, and the [vertical] movement is, at least a component of precession, and follows the "laws" of gyroscopic behavior. We could probably use some professional help here - however, I believe that the my statement (above) is correct.
I believe that I read this either in Modern Exterior Ballistics, by Robert McCoy (had to read that one four times!
), or, Rifle Accuracy Facts, by Harold Vaughn, or, both. 
RGDang, the older you get the more you understand how little you really know!
The vertical component is also relative to twist rate. A good (eyes/hands on) test is via a precision rifle (one capable of reliable .25MOA), at two hundred yards: chose the RH (L to R) wind and a WINDY day, and deliberately shoot the pushes, let-ups, and everything between!
At a known muzzle velocity, one can obtain (calculate) a very close twist rate from the angle of dispersion, or, vice-versa.
The reason, again, for choosing the RH (L to R) condition, is that the vertical is usually more pronounced, as the gyroscopic movement is acting in conjunction with gravity, and thus easier to observe. This is an attribute of "wind drift" that the typical, "full, half, quarter value" wind chart does not display - they account only for L/R.When shooting my 25x47 LAPUA Hunter Class rifle (1:9" twist Bartlein/110 Gr. BT bullet combination), in competition, I must pay WAY MORE attention to angle changes than with either a 30x47 HBR, or 30BR (1:18" twist/112-118 Gr. bullet combinations)!
Especially, at 100 Yd., I have been much more prone to "drop" points - due to vertical - than with the slower (by 1/2) twist barrels! By the way, this is one reason that the 30 BRs are so great - the 17/18" twist barrels, relative the bullets lengths & mass, deliver solid gyroscopic stability (>1.5) at relatively low RPM - comparatively little wind induced vertical.
On a brief tangent, my primary use is to, before shooting a sighter, in a change, glance at the star and see where, relative to my ZERO, it should go, then shoot to confirm. If it behaves according to the graph, I'm likely to drill another ten - pronto! In other words, to build confidence - after a while,
in most conditions, one can simply, "hold-off" for small variations, and do well, trusting the tune.
RG
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Here is good video on precession:
which does not explain the displacement of a bullet due to wind. The chart shows the effect of Magnus force which is shown in the video:
Better yet:
which does not explain the displacement of a bullet due to wind. The chart shows the effect of Magnus force which is shown in the video:
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Very interesting and well made video, however, I think we're looking at differing dynamics - according to the Magnus effect, vertical, associated with drift, would be just the opposite of my beloved star! And further, immeasurable. That would make me the luckiest, bassakwards point-blank BR competitor ever.
So, after watching the Magnus effect video, I scrounged up my copy of RIFLE ACCURACY FACTS, by Harold Vaughn, and read the pertinent information (pages 195 and 196): " Instead of the Magnus effect causing the vertical wind drift component, it is caused by gyroscopic moments similar to the yaw of repose that we just discussed." Mr. Vaughn did agree that, regarding vertical, the Magnus effect is much to small to consider. Yep, exterior ballistics is a set of complicated dynamic actions/reactions. Keep 'em ON the X! RG
Note: if you are unfamiliar with (the late) Mr. Vaughn, his credentials were pretty impressive; " In Sept, 1951, he joined Sandia National Laboratories, Albuquerque, NM, as a staff member in the Aerodynamics Dept. He was promoted to Supervisor, Aeroballistics Division in July 1959 - a position he held until his retirement from Sandia National Laboratories in 1986."
That would make me the luckiest, bassakwards point-blank BR competitor ever.So, after watching the Magnus effect video, I scrounged up my copy of RIFLE ACCURACY FACTS, by Harold Vaughn, and read the pertinent information (pages 195 and 196): " Instead of the Magnus effect causing the vertical wind drift component, it is caused by gyroscopic moments similar to the yaw of repose that we just discussed." Mr. Vaughn did agree that, regarding vertical, the Magnus effect is much to small to consider. Yep, exterior ballistics is a set of complicated dynamic actions/reactions. Keep 'em ON the X! RG
Note: if you are unfamiliar with (the late) Mr. Vaughn, his credentials were pretty impressive; " In Sept, 1951, he joined Sandia National Laboratories, Albuquerque, NM, as a staff member in the Aerodynamics Dept. He was promoted to Supervisor, Aeroballistics Division in July 1959 - a position he held until his retirement from Sandia National Laboratories in 1986."
Very interesting and well made video, however, I think we're looking at differing dynamics - according to the Magnus effect, vertical, associated with drift, would be just the opposite of my beloved star! And further, immeasurable.
So, after watching the Magnus effect video, I scrounged up my copy of RIFLE ACCURACY FACTS, by Harold Vaughn, and read the pertinent information (pages 195 and 196): " Instead of the Magnus effect causing the vertical wind drift component, it is caused by gyroscopic moments similar to the yaw of repose that we just discussed." Mr. Vaughn did agree that, regarding vertical, the Magnus effect is much to small to consider. Yep, exterior ballistics is a set of complicated dynamic actions/reactions. Keep 'em ON the X! RG
Note: if you are unfamiliar with (the late) Mr. Vaughn, his credentials were pretty impressive; " In Sept, 1951, he joined Sandia National Laboratories, Albuquerque, NM, as a staff member in the Aerodynamics Dept. He was promoted to Supervisor, Aeroballistics Division in July 1959 - a position he held until his retirement from Sandia National Laboratories in 1986."
The original chart shown was probably for smallbore shooters which are affected by magnus force. The magnus force effect on centerfire is negligeable; but, after viewing the video, I do agree, that spin drift may be due to precession caused by side winds.
USMCDOC
Silver $$ Contributor
The original chart is the one that is used exclusively around my parts by rimfire br guys..
I'm sorry but it ALSO must be said that, "that "sniper 101" dude is an idiot".......he's so far out of his depth he doesn't even realize he's no longer in the pool....
I'm sure this whole jacking together of unrelated video stuff all flies without question on "The Heide" and "Sniper's Parodies" type forums but there are people here who actually care to learn truth.
For those who really want to know, follow Randy's advice and read some actual real ballistics texts like McCoy or Vaughn, folks who actually understood whereof they spoke VS those "ballisticians" just imperfectly parroting the work of others.
I remember once in conversation with Harold I asked him about one of the sillinesses passed on in this video (((and in most ballistical rewrites.....)))) Specifically the idea that the oft-cited Yaw Of Repose increases BC. And I vividly remember his reply. After taking in the proposition (so absurd that he didn't know it existed) he shook his head like an old dawg and said "I have no reply! I can't begin to argue with that level of stupid!"
Using "Magnus Effect" comparing curving balls and "Bernoulli's Principle" comparing water-bending techniques and then adding ho'made sillinesses involving garden hoses to explain vertical drift is simply too silly to argue with!
Simply put, "spin-drift" and "wind-drift" and even "vertical drift" are all drag effects, easily rectified using known drag models and tests. They aren't mysterious nor do they need Capitalized Name Effects/Principles/Syndromes associated with them.
I'm sure this whole jacking together of unrelated video stuff all flies without question on "The Heide" and "Sniper's Parodies" type forums but there are people here who actually care to learn truth.
For those who really want to know, follow Randy's advice and read some actual real ballistics texts like McCoy or Vaughn, folks who actually understood whereof they spoke VS those "ballisticians" just imperfectly parroting the work of others.
I remember once in conversation with Harold I asked him about one of the sillinesses passed on in this video (((and in most ballistical rewrites.....)))) Specifically the idea that the oft-cited Yaw Of Repose increases BC. And I vividly remember his reply. After taking in the proposition (so absurd that he didn't know it existed) he shook his head like an old dawg and said "I have no reply! I can't begin to argue with that level of stupid!"
Using "Magnus Effect" comparing curving balls and "Bernoulli's Principle" comparing water-bending techniques and then adding ho'made sillinesses involving garden hoses to explain vertical drift is simply too silly to argue with!
Simply put, "spin-drift" and "wind-drift" and even "vertical drift" are all drag effects, easily rectified using known drag models and tests. They aren't mysterious nor do they need Capitalized Name Effects/Principles/Syndromes associated with them.
You may think of him as an 'idiot' but he is correct in explaining Magnus Effect except for not mentioning the physical cause from boundary layers. Magnus Effect is a lift phenomenon and not a drag phenomenon.
Neither of which apply to supersonic projectiles EVER, there are no boundary effects pertinent to SS flight, and even in subsonic (22LR) the Magnus Effect is completely irrelevant. Rationalize rotational velocity to flight velocity to see this.
Bullets Do Not Roll On The Air
they aint like basketballs.
In fact, the wind never even TOUCHES the side of the projectile......unless you're launching your bullets sidewise, like David slewing Goliath....
Dude didn't "explain" anything BTW
And as to this statement "Magnus Effect is a lift phenomenon and not a drag phenomenon." I'll just say OK
The crosswind is subsonic and not supersonic. Boundary layers are present at ALL speed regimes.
Basketballs, golf balls and yes, bullets obey the same law of physics
I don't preach much......perty much burnt out there...... but if I may suggest politely, read Franklin W Mann available free here on this site http://www.accurateshooter.com/book-dvd-reviews/free-downloadable-classic-gun-books/
Mann tried to rectify bullet 'flight' using your rationale. He even built a shooting tunnel (and he was not a rich man.)
Depart123
If I were going to quote a source to support my argument on a set of scientific principles, I probably wouldn't pick one that wasn't published in 1909.....just sayin'.
OOOPs
- from L to R, or, traveling to the right. Bad on me for having to edit this response - you see how easily confused old age is making me? RGP.S. L to R drags the bullet to the right . . . for yours truly, that's the most difficult concept to grasp.
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butchlambert
Site $$ Sponsor
I love that! "just saying" So the date of publishing establishes the veracity of the subject. Gimme a break!
Yep, with a good rifle, just shoot and trust the sighters - and our judgement! In point-blank BR, we can do that, and see where they hit, at any time during the 7 minutes we have to complete our record target(s)!
But, it's nice to understand why they go where they do. In the long run, understanding leads to winning - if one is, "into that". Keep 'em ON the X! RG
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