Missed shot due to Magnus Effect?


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Strakele
June 30, 2008, 02:23 PM
While at the Air Force Academy a few weeks back I was in an engineering seminar and one thing they discussed was the Magnus Effect, which was noted for its effect on the point of impact for artillery rounds.

For those of you not familiar, here's the basics: http://en.wikipedia.org/wiki/Magnus_effect

From Wikipedia:
The Magnus effect can be found in advanced external ballistics. A spinning bullet in flight is often subject to a sideways wind. In the simple case of horizontal wind, the Magnus effect causes an upward or downward force that depends on the direction of the wind which affects the projectiles point of impact. Even in completely calm air, a bullet will experience a small sideways wind component. This is because bullets have a yaw motion that causes the nose of the bullet to point in a slightly different direction from the direction in which the bullet is actually traveling. This means that the bullet is "skidding" sideways at any given moment, and thus experiences a small sideways wind component. (yaw of repose) All in all, the effect of the Magnus force on a bullet is not significant when compared to other forces such as drag. However, the Magnus effect has a significant role in bullet stability because the Magnus force does not act upon the bullet's center of gravity, but the center of pressure. This means that the Magnus force affects the yaw of the bullet. The Magnus effect will act as a destabilizing force on any bullet with a center of pressure located ahead of the center of gravity, while conversely acting as a stabilizing force on any bullet with the center of pressure located behind the center of gravity. The location of the center of pressure depends on the flowfield structure, in other words, it depends on whether the bullet is in super-sonic or sub-sonic flight. What this means in practice depends on the shape and other attributes of the bullet. In any case the Magnus force greatly affects stability because it tries to "twist" the bullet along its flight path, twisting it either towards the axis of flight (stabilizing) or away from the axis of flight (destabilizing).

So this got me to thinking. When we shoot long range, we must of course account for the distance the bullet will drift due to wind. We look at our ballistics chart and find that at say 1000 yards, the bullet will drift X number of inches in a 10mph crosswind. However, that number does not take into account what direction the wind is coming from. The rifling in our barrel causes the bullet to spin a certain direction. According to the Magnus Effect, all other variables being exactly the same, the bullet will hit in a different place if the wind is coming 90 degrees from the left versus coming 90 degrees from the right. Is there any way to account for this? Is the effect even big enough to worry about? Or it it more like the Coriolis effect in that, while it's there, it doesn't make much of an impact over a (relatively) short 1000 yards?

Just something that got me to thinking. Perhaps this is well known and I just hadn't heard the name for it before. What do you guys think?

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LJ-MosinFreak-Buck
June 30, 2008, 02:48 PM
Okay, so I marginally understand this(^^), but now how does the corialis effect work on long range shooting? I've looked it up on wiki but it doesn't seem to make sense. If someone could also explain this.

sorry, OP.

Frog48
June 30, 2008, 02:51 PM
Interesting stuff.

But I never shoot far enough to have to worry about it. :D

hankdatank1362
June 30, 2008, 02:55 PM
Ok so I've read Understanding Firearm Ballistics cover to cover, more than once. Still, I doubt I could explain the physics behind the factors of Coriolis, spin drift (gyroscopic drift), the effects of wind friction at different angles of intersection (and at different stages of bullet flight), bullet flight time, etc... without screwing something up and sounding like a complete tool.

It's time for a Zak Attack.

The Sniper's Hide would also be a good place to ask these kind of questions.

Cosmoline
June 30, 2008, 02:59 PM
I find that almost all my missed shots are the direct result of the Magnus effect and the Coriolis effect. That plus the impact of high speed subatomic particles. And the annoying guy next to me with the muzzle brake. In fact I have never missed a shot due to my own inability to hit the target.

rcmodel
June 30, 2008, 03:16 PM
What do you guys think?I think you are thinking too much, and you are going to hurt your brain! :D


Seriously, wind is a huge factor at 1,000 yards, and yes, it makes a big difference if it is coming from the left, right, quartering, etc.

The problem is, the wind may be blowing a 10 MPH from the right at the firing line, 15 MPH quartering at 450 yards, and some other direction & speed at the 1,000 yard target.

That makes reading wind flags, grass, etc. through the scope vitally important.
There is no chart that can account for actual range conditions all the time.

rcmodel

cracked butt
June 30, 2008, 06:01 PM
*ponders the number of Angels that can dance on the head of a pin*

There are all kinds of other tiny factors that can affect the bullet's flight downrange. You'l keep your sanity if you keep a log of conditions, wind speed and direction, temperature, sun position, etc. Trying to find your no-wind zero is like hitting a constatly moving target, but if you put enough data together on where your bullet hits under different conditions, you can reasonably figure out where the zero is on your rifle and how to adjust it to ambient conditions. Worry about the details that you can do something about:cool:

Dr. Tad Hussein Winslow
June 30, 2008, 06:06 PM
So THAT's why my shots are all over the place! Zak attack - hee hee.

Strakele
June 30, 2008, 07:45 PM
Alright alright... I realize that compared to other factors this doesn't have as much an effect on the flight of the bullet. Just something I learned that I thought was interesting and involved shooting. I know wind varies a lot over long range but I still think this will effect the impact of the bullet to a degree, and I wondered if this was another thing that ultra long range shooters try to compensate for.

redneckrepairs
June 30, 2008, 07:59 PM
IMHO its not a concern with any round one is likely to fire from a man portable rifle . For one thing your ammo is likely to open a group up due to variances in the rounds more than the Magnus Effect at any range you might shoot at . It would however be at least as good an excuse for a miss as " the sun was in my eyes " imho lol .

nyggis
June 30, 2008, 08:21 PM
I find that almost all my missed shots are the direct result of the Magnus effect and the Coriolis effect. That plus the impact of high speed subatomic particles. And the annoying guy next to me with the muzzle brake. In fact I have never missed a shot due to my own inability to hit the target.

This is beautiful sarcasm! Keep going!!! :D

GearHead_1
June 30, 2008, 08:25 PM
I have resolved this issue and it is no longer a problem. I now only shoot in a vacuum at zero gravity. :D

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