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Author Topic: Ice Bullet question
Gerard Morvan
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I recently saw that episode of Mythbusters in which the myth of the Ice Bullet (taht is, that it's possible to kill a man with a bullet made of ice that, by melting in the body, leaves no trace) was revisited and busted. However, by thinking about it, I may have found a method by which this particular legend could be plausible.

Adam and Jamie have used ordinary, gunpowder, rifle for their experiments, and of course, the heat caused by the explosion has vaporised their bullets. But what if they had used airguns? Compressed air rifles have been around for a long time (Napoleon's troops had to deal with insurgents armed with them in Germany), and has it doesn't use something that causes such a big deal of heat, it could be possible for an ice bullet to stay in shape.

Of course, it could also be possible that the ice would break into tiny fragments. So, what's your opinion on this subject?

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Cervus
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I have no idea if your method would be possible, but you can always write to them and suggest it. Their staff does indeed read the Discovery Channel messageboards and emails. However, hundreds of people write in every week with suggestions of how they could redo an experiment to make it work, so the chances of them acknowledging someone else's particular method are slim.

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Silas Sparkhammer
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Any teenager with an iced soda and a straw can attest that one form of air gun is quite capable of firing a projectile made of ice: a blow-gun. I see no reason that a 1/2 inch bore blow-gun, perhaps five feet in length, couldn't fire a sharpened projectile made of ice with *potentially* lethal results. However, the actual lethality would be iffy. I can pretty much assure you of breaking unprotected skin, or putting out an eye if you hit it.

Given a "Sebastian Moran" model air-rifle (created by von Herder, the blind German mechanic) I would think that a projectile of ice could be launched with a high probability of lethality.

Also: isn't it possible to "harden" ice? Aren't there techniques involving melting the surface and re-freezing that produces a tougher structure? I know that you can produce a very clear form of ice; is there a harder form?

Silas

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vtsquire
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quote:
Adam and Jamie have used ordinary, gunpowder, rifle for their experiments, and of course, the heat caused by the explosion has vaporised their bullets. But what if they had used airguns? Compressed air rifles have been around for a long time (Napoleon's troops had to deal with insurgents armed with them in Germany), and has it doesn't use something that causes such a big deal of heat, it could be possible for an ice bullet to stay in shape.

first of all, once you switch to an airgun, you're no longer using an ordinary gun, which is what the myth centers around. (being able to avoid tracing by barrel marks)Secondly, the weight of water is nowhere near that of lead. Thusly, the kinetic energy is way lower. You would now need an airgun that shoots ice at a far faster speed than a gun shoots a bullet. NOT LIKELY! Unless... you increase the amount of ice... at which point you're no longer talking about a bullet... but more of a bolt or ball of ice.

Taken together, this busts the myth. The point is to avoid tracing by having a melting bullet that has no barrel marks... the only solution for this myth is to use a completely different gun.

BUSTED

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Electrotiger
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Personally, I'd like to see them build a magnetic railgun and shoot a sphere of ice with a ball bearing frozen in the center.

But that's just me.

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Finite Fourier Alchemy
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quote:
Originally posted by Silas Sparkhammer:
I see no reason that a 1/2 inch bore blow-gun, perhaps five feet in length, couldn't fire a sharpened projectile made of ice with *potentially* lethal results.

How do you sharpen ice? It's soft, weak, and won't take an edge. Even if it could, it won't keep an edge. Above freezing, the edges melt and round off. Below freezing, the edges sublimate and round off.

You can carve the stuff if you're skilled enough, but I've never seen sharp pointed edges on ice sculptures.

quote:
However, the actual lethality would be iffy. I can pretty much assure you of breaking unprotected skin, or putting out an eye if you hit it.
At close distance it's probably like throwing gravel, or poking someone with a stick. Damaging an eye is pretty easy, but breaking the skin with a small ice projectile seems a bit difficult. I'd expect an ice projectile to work a lot like a paintball projectile, with similarly low lethality.

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Troberg
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quote:
How do you sharpen ice? It's soft, weak, and won't take an edge. Even if it could, it won't keep an edge. Above freezing, the edges melt and round off. Below freezing, the edges sublimate and round off.
It's not soft, it's actually almost as hard as concrete, but it's brittle. That's why it's not possible to get a good edge.

On the other hand, if all we want to achive is to avoid leaving a traceable bullet, why not use something other than water that's a liquid at room temperature? What about mercury? Does it even have to be liquid at room temperature, isn't it enough if the impact energy turns it into a liquid?

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diddy
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quote:
On the other hand, if all we want to achive is to avoid leaving a traceable bullet, why not use something other than water that's a liquid at room temperature? What about mercury?
I would hope that an autopsy official would find the mercury.

Air gus just dont work at anything besides extremely close distances and by that point its just more effective to stab the guy. Water has about 1/12 the density of lead. It wont work, its far too brittle.

quote:
Also: isn't it possible to "harden" ice? Aren't there techniques involving melting the surface and re-freezing that produces a tougher structure? I know that you can produce a very clear form of ice; is there a harder form?
The guys tested this, it had no effect.

Air guns get posted to death on the discovery forums and people have explained dozens of times why it wont work as an efffective bullet. It has effectivcely been asked and answered there.

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jimmy101
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quote:
Originally posted by vtsquire:
... the weight of water is nowhere near that of lead. Thusly, the kinetic energy is way lower. You would now need an airgun that shoots ice at a far faster speed than a gun shoots a bullet. NOT LIKELY! Unless... you increase the amount of ice... at which point you're no longer talking about a bullet... but more of a bolt or ball of ice.

But doesn't a lighter projectile have a higher muzzle velocity and therefore about the same kinetic energy as a heavier projectile? A heavier projectile carries farther than a light one but both light and heavy projectiles can be fired with sufficient energy to be lethal.
quote:
Taken together, this busts the myth. The point is to avoid tracing by having a melting bullet that has no barrel marks... the only solution for this myth is to use a completely different gun.
I agree, it would be very difficult to use an ice slug in a conventional gun. But just because Mythbusters couldn't figure out a way to do it doesn't mean it can't be done. Those two aren't the brightest people in the world. So, the myth was busted only in the use of an ice slug in a conventional firearm given the brains at Mythbusters.

It would not be difficult to make an air gun that would fire a 1/2 pound ice slug at say 500 mph. That hunk of ice would have more than 25 times the kinetic energy of a baseball thrown by a major league pitcher (~100mph). More than enough kinetic energy to kill a person. If you can get a fragile projectile moving fast enough it no longer behaves as if it is fragile. (Similar to a tornado driving a wood 2x4 through a brick wall.)

Heck, I've got a gun that'll launch a 1" diameter by couple inch long ice slug at perhaps 300 mph. I would not want to be hit by it. And, it would be impossible to trace the slug back to the weapon that fired it.

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Hero_Mike
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The density of lead is 11.34 times that of water. Ice is roughly 90% the density of water, so lead is roughly 12.6 times the density of ice.

To get the same kinetic energy (Ek = 1/2 * m * v^2), you need to increase the velocity by the root of 12.6, in order to compensate for the reduced mass. This is a factor of 3.55 - the ice bullet must travel 3.55 times as fast as a lead bullet of the same size, to have the same kinetic energy.

According to wikipedia :

quote:
Spring-piston guns seem to have a practical upper limit of 1200 ft/s (370 m/s) for .177 cal (4.5 mm) pellets. Higher velocities cause unstable pellet flight and loss of accuracy. Drag increases rapidly as pellets are pushed past the speed of sound, so it is generally better to increase pellet weight to keep velocities subsonic in high-powered guns.
It seems highly unlikely that an air gun can achieve the velocities required to make a lethal ice bullet of the same size.

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DemonWolf
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quote:
Originally posted by Finite Foreigner Alchemy:
quote:
Originally posted by Silas Sparkhammer:
I see no reason that a 1/2 inch bore blow-gun, perhaps five feet in length, couldn't fire a sharpened projectile made of ice with *potentially* lethal results.

How do you sharpen ice? It's soft, weak, and won't take an edge. Even if it could, it won't keep an edge. Above freezing, the edges melt and round off. Below freezing, the edges sublimate and round off.

You can carve the stuff if you're skilled enough, but I've never seen sharp pointed edges on ice sculptures.

You wouldn't need it to be sharp, just aerodynamic. Most bullets aren't sharp either.
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Aptenodytes_Forsteriis
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If you really want to leave no evidence dry ice would be the way to go. It'll sublimate and leave no residue, unlike ice whick would leave a wound full of water.

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DemonWolf
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quote:
Originally posted by Aptenodytes_Forsteriis:
If you really want to leave no evidence dry ice would be the way to go. It'll sublimate and leave no residue, unlike ice whick would leave a wound full of water.

Dry ice may leave "frostbite" damage to tissiue. But then again, that may confuse investigators more than water!

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jimmy101
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quote:
Originally posted by DemonWolf:
You wouldn't need it to be sharp, just aerodynamic. Most bullets aren't sharp either.

Most bullets are not aerodynamic. Indeed they are extremely non-aerodynamic. That is why they are generally fired from a rifled barrel. The rifling spins the bullet and gyroscopic forces keeps it from tumbling.

The only "aerodynamic" standard bullet shape I know of is a round ball.

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Aptenodytes_Forsteriis
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quote:
Originally posted by DemonWolf:
quote:
Originally posted by Aptenodytes_Forsteriis:
If you really want to leave no evidence dry ice would be the way to go. It'll sublimate and leave no residue, unlike ice whick would leave a wound full of water.

Dry ice may leave "frostbite" damage to tissiue. But then again, that may confuse investigators more than water!
Actually, since we're playing with super high powered air guns any way, why do we need a projectile? Compress the air enough that it comes out at 3-5000 FPS and I'll bet the blast itself will tear tissue apart.

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jimmy101
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quote:
Originally posted by Hero_Mike:
The density of lead is 11.34 times that of water. Ice is roughly 90% the density of water, so lead is roughly 12.6 times the density of ice.

To get the same kinetic energy (Ek = 1/2 * m * v^2), you need to increase the velocity by the root of 12.6, in order to compensate for the reduced mass. This is a factor of 3.55 - the ice bullet must travel 3.55 times as fast as a lead bullet of the same size, to have the same kinetic energy.

According to wikipedia :

quote:
Spring-piston guns seem to have a practical upper limit of 1200 ft/s (370 m/s) for .177 cal (4.5 mm) pellets. Higher velocities cause unstable pellet flight and loss of accuracy. Drag increases rapidly as pellets are pushed past the speed of sound, so it is generally better to increase pellet weight to keep velocities subsonic in high-powered guns.
It seems highly unlikely that an air gun can achieve the velocities required to make a lethal ice bullet of the same size.
All good points there. An ice bullet of the same dimensions as a lead bullet is going to have less kinetic energy. But a bullet does not have to have the kinetic energy of a modern rifle bullet to be lethal.

Furthermore, nobody said the ice bullet had to have the same dimensions as a lead bullet. Only that it can be fired from a conventional gun. If the ice bullet is ten times longer than a lead bullet the total weight of the two rounds would be similar. The muzzle velocities and kinetic energies would also be close. Heck, it is easy enough to calculate exactly how long the ice bullet would need to be to have the exact same mass as a lead bullet of defined length and caliber.

Generally, air guns are limited to muzzle velocities less than the speed of sound. (Since you can't get air moving through a pipe at speeds greater than the speed of sound.) At short range, that may be sufficient. A light-weight round at short range can easily have the same kinetic energy as a much heavier round at long distance.

An air gun can be easily built that will fire a much bigger ice slug. The spudgun community regularly builds guns that'll fire a soda can size hunk of ice at several hundred miles per hour. Definitely a round capable of killing. Heck, a gun like that can be built for less then $50.

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Hero_Mike
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quote:
Originally posted by jimmy101:
quote:
Originally posted by Hero_Mike:
It seems highly unlikely that an air gun can achieve the velocities required to make a lethal ice bullet of the same size.

All good points there. An ice bullet of the same dimensions as a lead bullet is going to have less kinetic energy. But a bullet does not have to have the kinetic energy of a modern rifle bullet to be lethal.

Furthermore, nobody said the ice bullet had to have the same dimensions as a lead bullet. Only that it can be fired from a conventional gun. If the ice bullet is ten times longer than a lead bullet the total weight of the two rounds would be similar. The muzzle velocities and kinetic energies would also be close. Heck, it is easy enough to calculate exactly how long the ice bullet would need to be to have the exact same mass as a lead bullet of defined length and caliber.

Generally, air guns are limited to muzzle velocities less than the speed of sound. (Since you can't get air moving through a pipe at speeds greater than the speed of sound.) At short range, that may be sufficient. A light-weight round at short range can easily have the same kinetic energy as a much heavier round at long distance.

An air gun can be easily built that will fire a much bigger ice slug. The spudgun community regularly builds guns that'll fire a soda can size hunk of ice at several hundred miles per hour. Definitely a round capable of killing. Heck, a gun like that can be built for less then $50.

Okay, back to science class...

I don't think that anyone said that the ice bullet had to have the same kinetic energy as a modern rifle bullet. It could have the same kinetic energy as a small handgun bullet. Regardless of what it is compared to, it must have a sufficiently lethal kinetic energy.

That said, it would need to have 3.55 times the velocity of a lead bullet *of equal size* to compensate for an *equivalent kinetic energy*. But an ice bullet that is very long is not likely to be a very good projectiile (there's a reason why bullets are of all sizes have a fairly narrow range of diameter to length). And ice is not very strong - a long, brittle bullet is not likely to remain in one piece. So firing an ice bullet with a non-standard shape, from a conventional gun is also not likely.

I mentioned the air gun being unlikely because it was mentioned in the thread that a problem with firing an ice bullet from a conventional gun was that the temperature of powder combustion damaged the bullet. This is the issue here, right? That an ice bullet is fragile and not likely to survive being propelled at sufficient speed to make up for the significantly lower density than that of your typical lead bullet.

But jimmy101, then you mention that a "spud gun" can be used to fire a pop-can sized ice projectile at lethal kinetic energy levels. Such a gun and projectile are very much non-conventional, and are not likely to have any kind of range or accuracy, not to mention portability. (I think that the idea here is to use a bullet made from ice, from a regular handgun because regular handguns are not only common, they are also very portable and easily concealed.) This is very contradictory to this statement that *you* make earlier :

quote:
...nobody said the ice bullet had to have the same dimensions as a lead bullet. Only that it can be fired from a conventional gun.
Getting into the realm of spud guns is contradciting your own "conditions" here.

Another simple answer is to use dry ice (frozen carbon dioxide) - it has a density 1.6 times that of air. This requires that the dry ice bullet be only 2.65 times as fast as a lead bullet of equivalent size - much more reasonable than the ratio for a "water ice" bullet.

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"The fate of *billions* depends on you! Hahahahaha....sorry." Lord Raiden - Mortal Kombat

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jimmy101
The First USA Noel


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quote:
Originally posted by Hero_Mike:
Okay, back to science class...

I don't think that anyone said that the ice bullet had to have the same kinetic energy as a modern rifle bullet. It could have the same kinetic energy as a small handgun bullet. Regardless of what it is compared to, it must have a sufficiently lethal kinetic energy.

Exactly. The ice does not have to be moving at 2000 fps (typical modern rifle) nor does it have to have the mass or density of a lead bullet. It Just needs sufficient kinetic energy. The question of course is "how much energy is sufficient?" Modern guns are grossly overpowered compared to what is actually needed to kill at short range. How much KE do you actually need? 1/2, 1/10, 1/100 of say the KE of a typical handgun? I suspect you can get enough KE with an ice slug. Can't prove it but I've built enough guns to believe that with a little fiddling (longer projectile, reduced powder charge etc) that it can be done. Mythbusters spending a couple hours trying to do it hardly constitutes an exhaustive effort.

quote:
Her I (jimmy101) have omitted many valid points from the opposing person.
quote:
But jimmy101, then you mention that a "spud gun" can be used to fire a pop-can sized ice projectile at lethal kinetic energy levels. Such a gun and projectile are very much non-conventional, and are not likely to have any kind of range or accuracy, not to mention portability. (I think that the idea here is to use a bullet made from ice, from a regular handgun because regular handguns are not only common, they are also very portable and easily concealed.) This is very contradictory to this statement that *you* make earlier :

quote:
...nobody said the ice bullet had to have the same dimensions as a lead bullet. Only that it can be fired from a conventional gun.
Getting into the realm of spud guns is contradciting your own "conditions" here.
Sorry, did wander a bit. Just trying to make the point that "a lethal ice bullet" is definetly possible, especially if you are not constrained to a predefined concept of what a gun is.
quote:
Another simple answer is to use dry ice (frozen carbon dioxide) - it has a density 1.6 times that of air. This requires that the dry ice bullet be only 2.65 times as fast as a lead bullet of equivalent size - much more reasonable than the ratio for a "water ice" bullet.
Trivial error, I assume you mean 1.6 times ... water, not air?

The problem with using dry ice is that as it sublimes the CO2 gas generated would tend to force the slug out of the barrel. To minimize sublimation, the gun barrel would have to be colder than dry ice (-70C IIRC). That is even more impractical than having the barrel at 0C to keep the ice from melting.

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MaxGunnar
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Freeze water and sawdust, hard as concrete, experiments were done in GB and Canada to check the fesibility of building a huge floating airfield with it. History Channel
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Finite Fourier Alchemy
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quote:
Originally posted by DemonWolf:
You wouldn't need it to be sharp, just aerodynamic. Most bullets aren't sharp either.

Well, yeah, but Silas's post was about a blowgun dart, which is different from a bullet. They travel much slower, so they need a small cross-sectional area to penetrate a target.

Reviewing the thread, it looks like the somewhat scattered consensus is this: An ice bullet is possible, provided that one of two conditions is met:

1. the bullet is not made of ice

2. the ice is not made into a bullet

to which I completely agree. [Smile]

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Mouse
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I thought an ice dagger was supposed to be the undetectable weapon.

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"I distrust who know so well what God wants them to do because I notice it always coincides with their own desires." -- Susan B. Anthony

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Sasquatch
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I bet the sawdust version would go a long ways to holding the ice bullet together, but the sawdust would leave it's own evidence. It might even be DNA matchable to the original board/tree.

Personally, I've always wanted to try a Cesium bullet, not only would it consume itself and leave no remnants, it would undoubtably increase the lethality of the wound.

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Unusual Elfin Lights
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I do have a bit of a background in ballistics. Couple this with Hero Mike's background in physics and I think we can have an answer.

One thing about increasing the amount of ice to increase the kinetic energy. Ballistics has shown that anytime the projectile length gets over 7 times the calibre, the projectile is ballistically unstable. So adding more water to a conventional chamber will not get the results desired.

How I would attempt this experiment is two fold:

- wadding: I would use some form of base wadding to act as a buffer between the combustion of the propellant in the chamber and the cold base of the bullet. This will, hopefully, reduce the amount of melting that will severely impact the bullet flight.

- sabot: modern tanks fire a round called APFSDS which stands for Armoured Piercing, Fin Stabilised, Discarding Sabot. This round has a 2.5 cm projectile that has a series of collars (sabots) around it. The sabots keep the projectile centred in the 10.5 cm barrel, they are the cause of obturation in the chamber, and once the projectile leaves the barrel, they fall away leaving only the projectile in ballistic flight. The charge used to propel this is the same as the charge for a 105 mm HESH round, but the muzzle velocities are greatly different. One advantage of the sabots is that they would be the ones absorbing the heat from the friction of the barrel, not the ice bullet.

For the experiment, I would use a larger calibre rifle, perhaps a .50 sniper variant. I would have a specially created round. This round would have the standard casing with propellant. In the projectile, I would have the base being a Teflon based “wadding” backed on the rear sabot. I would have a 7.62 mm ice projectile sitting in the sabots. I am a firm believer that 7.62 is needed to permanently stop a person. 5.56 is good, but not a guarantee. When fired, the Teflon wad would push the base of sabot pushing the rest of the projectile down the barrel. The spinning of the round would impart some stability in flight. Once the projectile has left the barrel, the wadding and sabots fall off and land within 50 metres. The bullet is able to fly for about 800 metres (my estimate based upon how the rifle shoots). Evidence at the target? Big hole. Evidence elsewhere? There will be some sabots and a piece of Teflon wad sitting near the sniper position.

The sound would still be quite loud, and the ability to hide a .50 is nearly impossible, especially skiing down a hill with Russians chasing you on snowmobiles…

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Ganzfeld
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I have a question about this that seems pertinant: How cold can powder be before it becomes useless? It seems you would want to have an ice bullet as cold as possible to limit the amount of vaporization or melting.
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Unusual Elfin Lights
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quote:
Originally posted by Ganzfeld:
I have a question about this that seems pertinant: How cold can powder be before it becomes useless? It seems you would want to have an ice bullet as cold as possible to limit the amount of vaporization or melting.

One problem with ice that is too cold is that it shatters when stress is placed upon it. Now whether an ice bullet would shatter anyways is up for conjecture, as its crystalline structure is not that strong.

For powder, though, are you talking the "gunpowder" or "powdered ice"?

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Troberg
Angels Wii Have Heard on High


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quote:
I would hope that an autopsy official would find the mercury.
I think we can assume they would find the bullet hole anyway. We must make a distinction between undetectable and untracable. As the effects of the hit will be plainly visible, we can pretty much forget undetectable, but we can achieve untracable.

On the other hand, if we just want to have an untraceable weapon, I'd go for an ordinary shotgun. As I understand it, shot gun pellets are not traceable. If I was an assassin, I'd sure prefer to use a proven technology rather than some experimental gamble.

quote:
Freeze water and sawdust, hard as concrete, experiments were done in GB and Canada to check the fesibility of building a huge floating airfield with it. History Channel
Not only airfields, and saw dust is not needed:

http://en.wikipedia.org/wiki/Ice_hotel

quote:
Most bullets are not aerodynamic. Indeed they are extremely non-aerodynamic. That is why they are generally fired from a rifled barrel. The rifling spins the bullet and gyroscopic forces keeps it from tumbling.
Hmm, this set my mind off on a tangent. Presumably, the most aerodynamic form is the shape of a water drop. I wonder how a bullet in that shape would work? It would have the center of gravity up front, with a tail to stabilize it, so it would probably be almost as stable in flight as a dart. The low drag would allow it to retain its energy longer, as well as giving it a flatter and longer trajectory. The lack of a pointed front would probably make it flatten on impact, but as it has the material in the tail working it's way forwards, the rear part of the bullet may provide some penetration, especially if made from a harder material.

Now, how to set up an experiment to test this, preferably surviving to see the results?

--------------------
/Troberg

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Hero_Mike
Happy Holly Days


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Taking into account some of the things that Yoo-ee-ell and MaxGunnar have said, it seems unlikely that a bullet can be made entirely of ice, without adding some other material (which is potentially tracable), or using a fancier "sabot" round which also suggests the use of a larger calibre weapon.

The best bet - and it still seems far-fetched - is a large calibre handgun (say 9mm) with a highly modified bullet - perhaps made from dry ice or a water/sawdust mixture. (The best way to avoid the tracability of the sawdust is to use sawdust from an engineered wood product - like plywood or MDF, which are commonly found and not made from only one distinct tree.) The charge and bullet shape will be optimized for enough short-range stopping power to be lethal, probably at the expense of any kind of range or accuracy - though handgun accuracy beyond even a few dozen yards is limited. You'll also have to keep the bullets cold - *very cold* - and while this may not affect the powder charge, it will also affect the dimensions of the metal casing. At sufficiently cold temperatures the casing will have shrunk enough to affect its fit in the firing chamber. Such a bullet, at higher temperatures, would be oversized.

Almost as important as the bullet itself would be a means of carrying them while frozen - a small "cooler" chilled by a sleeve of, say, liquid nitrogen, would keep everything frosty until the last minute, when you load your gun and "ice" your enemy.

The sublimating gas from a "dry ice" bullet would not be enough to force it out of the gun. If you hold a piece of dry ice in your hand, it does not leap away from it. The gas escape would be constrained, as is the bullet. A potential problem would be having your typical automatic pistol with the bullets in a magazine inside the grip - holding the gun for a long time will melt the bullets, and any melting will change the dimensions of the bullet - which is bad news. See above for solutions to this problem.

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"The fate of *billions* depends on you! Hahahahaha....sorry." Lord Raiden - Mortal Kombat

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Unusual Elfin Lights
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quote:
Originally posted by Troberg:
quote:
Most bullets are not aerodynamic. Indeed they are extremely non-aerodynamic. That is why they are generally fired from a rifled barrel. The rifling spins the bullet and gyroscopic forces keeps it from tumbling.
Hmm, this set my mind off on a tangent. Presumably, the most aerodynamic form is the shape of a water drop. I wonder how a bullet in that shape would work? It would have the center of gravity up front, with a tail to stabilize it, so it would probably be almost as stable in flight as a dart. The low drag would allow it to retain its energy longer, as well as giving it a flatter and longer trajectory. The lack of a pointed front would probably make it flatten on impact, but as it has the material in the tail working it's way forwards, the rear part of the bullet may provide some penetration, especially if made from a harder material.
The challenge of this type of form for a bullet is getting the maximum push during acceleration. The reason for the flat back of the bullet is that it can receive maximum force to push it up the barrel. If it has a tear shaped back some of the force will be spent compressing the bullet.
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DemonWolf
Ding Dong! Merrily on High Definition TV


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quote:
Originally posted by Yoo-ee-ell:
quote:
Originally posted by Troberg:
quote:
Most bullets are not aerodynamic. Indeed they are extremely non-aerodynamic. That is why they are generally fired from a rifled barrel. The rifling spins the bullet and gyroscopic forces keeps it from tumbling.
Hmm, this set my mind off on a tangent. Presumably, the most aerodynamic form is the shape of a water drop. I wonder how a bullet in that shape would work? It would have the center of gravity up front, with a tail to stabilize it, so it would probably be almost as stable in flight as a dart. The low drag would allow it to retain its energy longer, as well as giving it a flatter and longer trajectory. The lack of a pointed front would probably make it flatten on impact, but as it has the material in the tail working it's way forwards, the rear part of the bullet may provide some penetration, especially if made from a harder material.
The challenge of this type of form for a bullet is getting the maximum push during acceleration. The reason for the flat back of the bullet is that it can receive maximum force to push it up the barrel. If it has a tear shaped back some of the force will be spent compressing the bullet.
Not if we use a flat backed sabot.

--------------------
Friends are like skittles: they come in many colors, and some are fruity!

IMJW-052804

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Troberg
Angels Wii Have Heard on High


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quote:
Not if we use a flat backed sabot.
Or just add some extra propellant.

--------------------
/Troberg

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DemonWolf
Ding Dong! Merrily on High Definition TV


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quote:
Originally posted by Troberg:
quote:
Not if we use a flat backed sabot.
Or just add some extra propellant.
But if we add the extra propellant the force will still bend around the readward facing tip of the ice drop. The sabot will make the force push the drop much more effectively.

--------------------
Friends are like skittles: they come in many colors, and some are fruity!

IMJW-052804

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Ganzfeld
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quote:
Originally posted by Yoo-ee-ell:
For powder, though, are you talking the "gunpowder" or "powdered ice"?

I was assuming you'd want to have the bullet very cold and the gunpowder would, without sufficient insulation, also be cold. So I thought that would be one limitation.

True that you would rather have more elasticity in your ice but that would also allow the ice to vaporize easier, no?

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Arts Myth
The First USA Noel


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On the subject of untraceability, how about a bullet made of bone? Since any sort of untraceable bullet would be likely used in black-ops type assassinations, the shooter would presumably be a pro, so they'd only have to be sure that the shot hits bone. The resultant fragments would camouflage the remains of the bullet, which would be designed to shatter upon impact with the bone.

Why does this bring to mind those tooth-firing guns from Existenz..?

--------------------
Stupid, stupid rat creatures! - Bone
"The missionaries told us not to cut ourselves. It displeases Jesus." - Elsie Clews Parsons, Kiowa Tales, quoted in The Mourner's Dance, Katherine Ashenburg

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jimmy101
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For Troberg: Rain drops are not shaped like they are typically drawn, i.e., with a "tear-drop" shape. According to wiki they are either spherical or spheroids with a flat leading edge, it depends on how big the drop is. Furthermore, raindrops move pretty slow. The terminal velocity is usually in the range of 5~30 fps which is pretty slow. (A baseball's terminal velocity is about 100 fps.) So would a rain-drop shape work well at "bullet" like velocities?

For Yoo-ee-ell:
quote:
The challenge of this type of form for a bullet is getting the maximum push during acceleration. The reason for the flat back of the bullet is that it can receive maximum force to push it up the barrel. If it has a tear shaped back some of the force will be spent compressing the bullet.
I don't think the challenge is getting the maximum push during acceleration. The challenge is getting the maximum push the hunk of ice can handle, which is different constraint. Too much push and the round will disintegrate.

Can you provide a cite for the affects of the rounds butt shape? I would think the flat butt is just because of two things; (1) the shape of the butt doesn't make much difference (in the barrel anyway) and (2) a flat butt is easiest to make.

The force on the backend of a round is only a function of the area, not the shape. Given the amount of energy that is expended accelerating the round (and expanding the barrel) I would think the small amount of energy lost to compressing a pointed butt would be unmeasurable. The shape of the butt will affect air drag but that is a different matter. Besides, in this imaginary gun there is more than adequate power. Any standard modern round (even a .22) has sufficient energy to kill. Granted, not from skis at a range of a thousand meters but range is nowhere mentioned in the statement of the problem.

I think Yoo-ee-ell has several good ideas though. Clearly to get to the mass that Hero thinks is needed you would want a large caliber. Furthermore, a 0.22 "saturday night special" is still considered to be a lethal weapon (wouldn't bet my life on it one way or the other but it fits the statment of the problem.) To get to the mass that Hero thinks is needed we just need to get the slug of ice to have the mass of a 0.22 round (I know, very wimpy, no range, very minimal stopping power but again it fits the statement of the problem).

Lets say a 0.45 barrel, twice the diameter of the 0.22 and with 4x the area. Hero would like ~13x the volume in the ice as in the lead round to get the same total mass. We get 4x from the bigger barrel so we need the ice chunk to be about 3x longer than a 0.22 to get the same total mass. A 0.22 is what, 1/2" long? So we have an ~1.5" long ice slug of 0.45 caliber to get about the same mass as a 0.22 round. (Yes I know, a 0.22 sucks, but the ATF considers it a lethal firearm so it fits the statement of the problem.) Yoo-ee-ell would like the length to be no more than the 7x the caliber for stability. Not sure that stability really matters, the statment of the problem does not say this has to work at 1000', of even 100', it could be point blank where aerodynamics have little affect. Nonetheless, 1.5" x 0.45" is well within the 7:1 ratio needed.

Total Power: The problem does not appear to be power limited. You can always use more powder. Besides pretty much any standard round has enough power in the powder for a lethal round at short range. Too much power is probably more of a problem, if the rounds turns into a puff of snow it is not going to be very effective. Related to the total available power is how fast the power is released and how long the round can extract power from the charge. Again, given the constraint that the round has to hold together. So, it would seem that it might help to use a slow burning powder (like black powder or Pyrodex) and a long barrel.

Yoo's suggestion of wadding is probably a good idea. Even several layers of cloth will provide some protection to the ice. A greese saturated fabric, as used in muzzle loaders, may be even better. The wadding from a muzzle loader survives firing more or less intact with only minimal burning. Suggesting that waddingmay provide some protection to the ice. Yoo's also suggested a sabot which is also a possibilty but may require more work.

Construction of the round: If I was doing this I would freeze the round in situ. Load the weapon with a suitable blank round, perhaps add a little wax over the top of the blank for additional protection from the water. Add wading and/or sabot. Point the muzzle up and add sufficent water. Freeze the entire gun muzzle up. Guns and powder are not bothered much by sub-zero temperatures. Having the gun at say 20F when fired is not a problem.

You now have a weapon loaded with a round with the same mass as a 0.22. The round is considerably larger than a 0.22 so it will not have much range.

The biggest potential problem is the danger inherant in firing a weapon with a "round" literally frozen in the barrel.

I can't think of any reason why that wouldn't work. You may need to fine tune the powder charge (and perhaps use an even slower burning powder).

You are not going to have a weapon that is affective at 1000' but it should be adequate at short range.

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Hero_Mike
Happy Holly Days


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quote:
Originally posted by jimmy101:
Furthermore, a 0.22 "saturday night special" is still considered to be a lethal weapon (wouldn't bet my life on it one way or the other but it fits the statment of the problem.) To get to the mass that Hero thinks is needed we just need to get the slug of ice to have the mass of a 0.22 round (I know, very wimpy, no range, very minimal stopping power but again it fits the statement of the problem).

The most common way that a 22-calibre pistol is used as a lethal weapon is with a single shot, at close range, to the base of the skull of an already subdued opponent. It isn't a particularly "deadly" weapon in most other circumstances. Several episodes of CSI (and my own common sense) have taught me that the .22 bullet penetrates the skull but does not come out, bouncing around inside and creating all kinds of havoc. But a single shot from a .22 even from, say, 20 feet, is not likely to be lethal unless it hits a very sensitive "soft" area.

For any meaningful analysis of an "ice bullet" with "lethal" capabilities, it has to be at least as deadly as, say, a typical .38 "police special" revolver - the standard law enforcement sidearm for many years. Otherwise this expands exponentially to the point where an ice bullet is as "lethal" as an air gun pellet.

--------------------
"The fate of *billions* depends on you! Hahahahaha....sorry." Lord Raiden - Mortal Kombat

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