Wild Bullet Oscillations Possible?

[LynnJr]

Envelope
Since your shooting buddy is a physics graduate he will understand what is going on clearly.
Tell him you are shooting in the northern hemisphere and your using a right hand twist barrel.
Tell him your bullets are corkscrewing to the right.
Tell him the corkscrew matches the bullets arc.
Tell him the vapor trail corkscrew matches that of your bullets drop.
Tell him how long you can see the vapor trail.
Ask him what happens to the bullets vapor trail over time.
He will be able to answer your questions without "Grand Illusions" or crazy talk.

[rsrocket1]

Thanks, your video post helped me find at least one of the other videos I was looking for.

Most of them fly in a corkscrew pattern, 1 actually curves!

Except these are severely mutilated bullets. I think the aerodynamics are the big factor here rather than the unbalanced weight, maybe not.

In fact, this video was the inspiration for me to try capturing my bullet flights myself. I recall being able to see 22LR shots in flight several times while shooting out in the hills with a dark background and figured it would not be too difficult to capture most any bullet maybe even at full speed. I decided to try at 1/4 speed slow motion just for the "cool" factor.

[JMP]

This thread is pretty funny. However, I think there is a disconnect in terminology. Do the bullets bend or oscillate?

Oscillation is a repeated pattern that occurs with bullets through precession, which really would not be observable in this case with the naked eye.

You will, however, witness an arc if you see the vapor trail. Watching the vapor trail is deceptive as it isn't static and the perceived action is different from what's actually happening to the bullet. Generally, speaking, the vapor trail doesn't appear as the true path of the bullet, rather, it gives the optical perception of the total travel in a condensed period. Hence, this is why rifle bullets appear to "bend" into the target. Even though the magnitude of change increases with distance, the perceived movement in flight is condensed toward the end.

Being in the northern hemisphere doesn't mean beans shooting a projectile 100 meters in less than 1 second. The Coriolis effect is dependent on the effective angular velocity of your frame of reference, so it's dependent on latitude. At the poles, the effective angular velocity is the greatest, so the effect is the largest. However, with rifles, even at very long distances the effect is extremely small from a CA latitude.

When I shoot, I factor in the Coriolis effect mainly because it is easily calculable and is now a standard feature on ballistic calculators. However, it's just a baseline, then you need to observe what is your best interpretation of what will happen in real life due to the winds and the Coriolis effect is absolutely trivial in your ultimate adjustment. The Coriolis effect, in the context of weaponry, is much more significant with heavy artillery fired at several miles. Northern hemisphere/southern hemisphere, that doesn't mean jack with 9mm.

Jr's depiction of what he has observed is factual; however, it sounds like he doesn't completely understand the the underlying physical causes of why he sees what he sees.

[JMP]

Except these are severely mutilated bullets. I think the aerodynamics are the big factor here rather than the unbalanced weight, maybe not.

It isn't purely aerodynamics, though, the altered aerodynamic properties may introduce an additional torque to the rotation, which exacerbate the natural oscillation that will be inherent in severely unbalanced bullets as the moment of inertia changes. As a mundane example, look at the mechanism that cause your tumbler to vibrate if you have a vibratory tumbler. It's an asymmetric rotating disk that generates forces on the machine in different directions.

[M1NM]

Wow man I can see the bullets. We need to get you off the LSD.

[thenodnarb]

This thread is pretty funny.

I agree.

Minute corkscrewing? Sure. 18" circles at 50 yards? I don't think so. That would mean if the pistol was fired perfectly, at 50 yards it might hit 18" to the right, but at 60 yards it might hit 18" low, 70 yards 18" left, 80 yards 18" high. Is that what we're talking about here? How does hickock 45 hit that gong at 80 yards? The bullets travel in an arc, affected by gravity and other ballistic factors but otherwise straight. If there is any corkscrewing, it is tiny.

[jonzer77]

I agree.



Minute corkscrewing? Sure. 18" circles at 50 yards? I don't think so. That would mean if the pistol was fired perfectly, at 50 yards it might hit 18" to the right, but at 60 yards it might hit 18" low, 70 yards 18" left, 80 yards 18" high. Is that what we're talking about here? How does hickock 45 hit that gong at 80 yards? The bullets travel in an arc, affected by gravity and other ballistic factors but otherwise straight. If there is any corkscrewing, it is tiny.

Maybe LynnJr is thinking about this?

http://m.basspro.com/Bass-Pro-Shops-Corkscrew-Bullet-Bottle-Opener/product/1306141334/

[krwada]

This thread is pretty funny. However, I think there is a disconnect in terminology. Do the bullets bend or oscillate?

Oscillation is a repeated pattern that occurs with bullets through precession, which really would not be observable in this case with the naked eye.

You will, however, witness an arc if you see the vapor trail. Watching the vapor trail is deceptive as it isn't static and the perceived action is different from what's actually happening to the bullet. Generally, speaking, the vapor trail doesn't appear as the true path of the bullet, rather, it gives the optical perception of the total travel in a condensed period. Hence, this is why rifle bullets appear to "bend" into the target. Even though the magnitude of change increases with distance, the perceived movement in flight is condensed toward the end.

Being in the northern hemisphere doesn't mean beans shooting a projectile 100 meters in less than 1 second. The Coriolis effect is dependent on the effective angular velocity of your frame of reference, so it's dependent on latitude. At the poles, the effective angular velocity is the greatest, so the effect is the largest. However, with rifles, even at very long distances the effect is extremely small from a CA latitude.

When I shoot, I factor in the Coriolis effect mainly because it is easily calculable and is now a standard feature on ballistic calculators. However, it's just a baseline, then you need to observe what is your best interpretation of what will happen in real life due to the winds and the Coriolis effect is absolutely trivial in your ultimate adjustment. The Coriolis effect, in the context of weaponry, is much more significant with heavy artillery fired at several miles. Northern hemisphere/southern hemisphere, that doesn't mean jack with 9mm.

Jr's depiction of what he has observed is factual; however, it sounds like he doesn't completely understand the the underlying physical causes of why he sees what he sees.

Do you shoot long distance regularly? It seems like you know quite a bit about external ballistics.

How do I find out more about this?

Thanks!
Ken

[JMP]

Maybe LynnJr is thinking about this?



http://m.basspro.com/Bass-Pro-Shops-...ct/1306141334/

That does appear to be a northern hemisphere/right twist model.

[LynnJr]

I doubt JMP shoots longrange very often if hes never seen a bullet do a half corkscrew to the target as was stated earlier.

Look at the picture posted by Carcaassone and do a google search to get accurate information.You won't find much here.

TheNodNarb
The bullet makes a half corkscrew to the target and has a 13 inch arc and any free ballistic program like jbm will show you the 13 inch arc.

This thread is actually quite sad and not really funny.

On a sunny day if you stand to the right hand side of someone shooting and about 4 feet behind them you can sometimes see this in full sunlight.The fact that none of you have witnessed this speaks volumes

If anyone wants to watch a 50 bmg bullet fly out to 2300 yards we shoot in Ukiah,Ca and can arrange a day were you shoot one of my 50 bmg's for free naturally and then you post what you witnessed without any illusions or magic tricks.

We could even make wagers on what you will observe with the proceeds to go to a youth shooting club or charity.

Oh yeah the northern hemisphere has nothing to do with coriolis in my earlier post.Maybe google search that as well.

[JMP]

I doubt JMP shoots longrange very often if hes never seen a bullet do a half corkscrew to the target as was stated earlier.

On a sunny day if you stand to the right hand side of someone shooting and about 4 feet behind them you can sometimes see this in full sunlight.The fact that none of you have witnessed this speaks volumes

As stated, I did not disagree with your observation. I don't think anyone else did either. To repeat:

Jr's depiction of what he has observed is factual; however, it sounds like he doesn't completely understand the the underlying physical causes of why he sees what he sees.

[thenodnarb]

So at what range do I aim 13" right to hit the target due to this corkscrew?Obviously we aren't talking about correcting for wind here. Silly me, I've been aiming right at the target all this time, only correcting for wind and drop.

[thenodnarb]

Does this video show the corkscrewing you're talking about?

[LynnJr]

TheNodNarb
You would hold 13 inches to the right in heavy winds.

The OP's posters observations of the vapor trail left by the bullet fired from a right hand twist barrel ARE PERFECTLY NORMAL.

The bullet is arcing as it goes downrange and this is around 10-22 inches depending on which bullet he is talking about.He shot a wide variety of bullet weights in his original post.
There is a cone of pressure around the bullet as it travels downrange and it is leaving a vapor trail as it goes downrange.The vapor trail expands with distance and time just like the wake behind a boat.He is observing the right hand helix because his gun has a right hand twist barrel.Had he been shooting a Colt pistol which have left hand twist barrels the helix would have twisted to the left rather than the right.

Carcassone has shown a image of what you would see using doppler radar but you have to remember that image is not to actual scale but greatly exaggerated.Those small circles inside the larger circles are magnified many times so you can see what is happening.You can't see the actual bullet in flight but at times you can see a copper colored flash coming from it.

To see what your bullets are actually doing you can paste a target or two backwards 7 yards in front of your muzzle while shooting at 100 yards.Most people call them Yaw cards but lightweight paper works just fine.
If your really ambitious you could do this all the way to 100 yards.

[thenodnarb]

Vapor trail I understand. It sounded as if you were saying the bullet travels in a corkscrew flight. Not just spinning due to twist rate, but a 13-18 in corkscrew.

All is well.