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Author Topic: Bullet spins like top on ice...  (Read 7439 times)

Mark Magyar

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Bullet spins like top on ice...
« on: May 20, 2011, 03:39:53 PM »

I don't happen to watch tv a whole lot but I was surfing the channels and Myth Busters happened to be on. They were testing this video to see if it could be confirmed or not.
http://www.youtube.com/watch?v=b1btKoF_HZk&feature=mfu_in_order&list=UL
Myth Confirmed.

Reminds me of the Chinese Whip Top video I've seen as the bullet is shaped similar to that of a whip top.
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Pulp

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Re: Bullet spins like top on ice...
« Reply #1 on: May 20, 2011, 05:01:56 PM »

What was the starting way of spinning?
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ta0

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Re: Bullet spins like top on ice...
« Reply #2 on: May 20, 2011, 06:32:05 PM »

I don't watch too much TV either, but I caught the preview and I HAD to watch it.  The TV guys could not at first reproduce it with slabs of ice in the summer but when they tried again in the winter during a snow storm it worked. It is pretty amazing that the bullet is stopped without being deformed. I guess the ice must become water (or vapor) instantaneously when the bullet hits.

Quote
What was the starting way of spinning?
The barrels of guns have grooves to impart spin to the bullets.  From Wikipedia: "Rifling is the process of making helical grooves in the barrel  of a gun or firearm, which imparts a spin to a projectile  around its long axis. This spin serves to gyroscopically  stabilize the projectile, improving its aerodynamic  stability and accuracy." Spinning rates can be over 300,000 RPMs!!!!  :o

Who would have thought that a gun could spin a top?  ;)

« Last Edit: May 20, 2011, 06:45:10 PM by ta0 »
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Pulp

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Re: Bullet spins like top on ice...
« Reply #3 on: May 21, 2011, 02:15:29 AM »

My question was if the bullet was putting in movement by a normal use of the gun, shooting directly to the ice...
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ta0

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Re: Bullet spins like top on ice...
« Reply #4 on: May 21, 2011, 09:38:50 AM »

Yes, somehow the ice stopped the bullet without deforming it and the bullet just kept spinning because of the spin given by the barrel. On the TV show the bullet ended up spinning while laying on the side but on the youtube videos they got some nice spins on the tip, just like a top.
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Jack

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Re: Bullet spins like top on ice...
« Reply #5 on: January 06, 2015, 12:37:54 AM »

« Last Edit: January 06, 2015, 12:45:59 AM by Jack »
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the Earl of Whirl

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Re: Bullet spins like top on ice...
« Reply #6 on: January 06, 2015, 04:42:02 AM »

Hmmm.  I don't remember this discussion from before.  We have some people in the congregation who do a lot with guns/rifles.  They will be interested in this.

The two videos that Jack posted don't spin as long as that first one but the last one shows a bullet spinning nearly on its side and somehow correcting itself so that it spins upright!
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kevinm

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Re: Bullet spins like top on ice...
« Reply #7 on: January 06, 2015, 07:30:19 PM »

^ That sure enough sounds like an Ohio thing. Mike, if you are going to film
it for youtube, remember to shout, "Hey y'all watch this!" before you start shooting.
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Austen

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Re: Bullet spins like top on ice...
« Reply #8 on: January 06, 2015, 10:04:54 PM »

We can try this out!!! We got plenty of bulletts but the Earl of whirl will have to bring the ice!!!
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the Earl of Whirl

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Re: Bullet spins like top on ice...
« Reply #9 on: January 09, 2015, 12:44:18 PM »

Just what I thought.  I showed them this video and they all got excited and started talking about how they could do it.  They just have to remember to first say "Hey y'all, watch this!"
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Dick Stohr

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Re: Bullet spins like top on ice...
« Reply #10 on: January 09, 2015, 02:23:44 PM »

I would like to know why the bullet does not go through the ice? Am I missing something? How thick/thin does the ice need to be? What size bullet and how much powder? Inquiring minds want to know!
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ta0

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Re: Bullet spins like top on ice...
« Reply #11 on: January 09, 2015, 03:10:20 PM »

I would like to know why the bullet does not go through the ice? Am I missing something? How thick/thin does the ice need to be? What size bullet and how much powder? Inquiring minds want to know!

My guess is that the kinetic energy of the bullet goes into the phase change from ice to water (or vapor). It is in fact a very interesting phenomenon and I would like to see some explanation or study about it.

I once read on a physics book that bullets travel a short distance in a liquid (e.g. water), no mater what their initial velocity is, because the faster they go the faster they need to move the material out of the way. On the other hand, making the bullet longer will make it go further, if I recall correctly.
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lincolnrick

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Re: Bullet spins like top on ice...
« Reply #12 on: January 09, 2015, 09:54:33 PM »

I would like to know why the bullet does not go through the ice? Am I missing something? How thick/thin does the ice need to be? What size bullet and how much powder? Inquiring minds want to know!

My guess is that the kinetic energy of the bullet goes into the phase change from ice to water (or vapor). It is in fact a very interesting phenomenon and I would like to see some explanation or study about it.

I once read on a physics book that bullets travel a short distance in a liquid (e.g. water), no mater what their initial velocity is, because the faster they go the faster they need to move the material out of the way. On the other hand, making the bullet longer will make it go further, if I recall correctly.

Mythbusters did a segment on bullets and water.  They shot various caliber pistols/rifles into a large pool and found that indeed, all projectiles loose most of their speed once they start traveling through water. From their webpage:

'All supersonic bullets (up to .50-caliber) disintegrated in less than 3 feet (90 cm) of water, but slower velocity bullets, like pistol rounds, need up to 8 feet (2.4 metres) of water to slow to non-lethal speeds. Shotgun slugs require even more depth (the exact depth couldn’t be determined because their one test broke the rig). However, as most water-bound shots are fired from an angle, less actual depth is needed to create the necessary separation.'
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Dick Stohr

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Re: Bullet spins like top on ice...
« Reply #13 on: January 10, 2015, 10:32:44 PM »

It makes sense that a bullet slows quickly in water but ice is a solid. Why does the bullet not penetrate in ice like it does in wood? I would think the ice would crack. How thick does the ice have to be to not crack? If you shoot bullets at concrete the bullet deforms and flattens, why not with ice?
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ta0

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Re: Bullet spins like top on ice...
« Reply #14 on: January 11, 2015, 12:05:30 AM »

It makes sense that a bullet slows quickly in water but ice is a solid. Why does the bullet not penetrate in ice like it does in wood? I would think the ice would crack. How thick does the ice have to be to not crack? If you shoot bullets at concrete the bullet deforms and flattens, why not with ice?
Shootest????????????????????????????????
In the first and third videos they seem to be shooting at snow and if it skips the surface some distance it is plausible that the bullet would slow down without deformation. On the second one the impact (at an angle) seems to be on real ice, but perhaps somewhat borderline. It does make a big crater what would explain the dissipation of the energy. What really surprises me is that in that case the bullet is not deformed.

A google search found this unclassified research by the US Army on projectile and fragment penetration in snow and frozen soil: link. Figure 13 shows penetration for different compact densities of snow and three calibers. In the conclusions section it says that aluminum FSP (flat soft point?) projectiles started to deform in snow at impact velocities greater than 900m/s.

Water is a very unusual material that behaves in strange ways. The results may depend drastically on the specific type of ice/snow that is impacted.
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