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Freeze!

literally
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The magazine of an air gun is cooled with liquid nitrogen or liquid helium. the gun shoots supercooled bullets that would stop muscle movement. it would be good for hostage situations and against body armor
AlexTheGreat, Jul 25 2006

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       The magazine of an air gun is cooled with liquid nitrogen and the shock waves from an exiting round shatter the metal :)
angel, Jul 25 2006
  

       it's a compressed air gun, no explosions or shockwaves
AlexTheGreat, Jul 25 2006
  

       No shockwaves? Just by changing the nature of the propellant? Just different shock waves.
normzone, Jul 25 2006
  

       Not clear why a supercooled bullet would stop muscle movement any more effectively than a metal one. Please explain.   

       If you're thinking a super-cooled bullet will freeze the muscle tissue around it, it won't do so any faster than a tranquilizer dart will subdue the target, i.e., too slowly to stop him/her shooting hostages, detonating a suicide bomb, etc.   

       Bad science/magic technology all around.
DrCurry, Jul 25 2006
  

       why would it be good against body armour? just more thermal insulation. Do you know anything about specific heats or thermal mass? To freeze or numb any large amuscles, you'd need either a) a small projectile with a huge specific heat that is very cold, or, b) a very large, very cold projectile made of normal materials. And whatever you use, a solid projectile would simply take too long to numb a muscle. and why is supercooling the barrel better than having a pre-supercooled projectile fired from a regular barrel?   

       And yes, judging by the thickness of the steel in most air gun barrels, there is some loading. I'm not sure shockwave is the right term, but some pretty high transient stresses. Expect a supercooled barrel to shatter.   

       I think reduced lethality lead-filled beanbag shotgun rounds would be far more reliable for immediate numbing of the target area. and they're baked too.   

       Or even a big taser gun. Oh hell, there's been lots of research into reduced lethality devices, and I'm not aware of any system using "cold" as the damaging energy. If something produces enough thermal flux to incapacitate someone very quickly, it'll probably cause massive frostbite and/or death. [/end rant/]   

       -
Custardguts, Jul 27 2006
  

       how about a water pistol, filled with liquid He   

       would that do the trick
j paul, Jun 30 2011
  

       If I'm held hostage, please don't experiment on me with any exotic weapons. Just shoot him/her, and me if you must, with old fashioned tech, please.   

       Okay, maybe just once with my popcorn machine gun.
normzone, Jun 30 2011
  

       I saw this in a bad childrens scifi movie. Even when I was 8 I thought it was dumb (-)
DIYMatt, Jul 01 2011
  

       I don't know specifically what is meant by the general reference to 'body armor,' but an air-powered rifle powerful enough to penetrate a kevlar vest and still have any stopping power would be prohibitively heavy to weild. If we're talking military-grade body armor with a steel chestplate, it's a two-man weapon, either with an incorporated compressor or with very few shots.   

       This is moot if you consider that super-cooled armor- piercing rounds would simply shatter when they struck the target, if not in the barrel of the gun.   

       As a personal rule, I do not throw bones, so I won't. But this is a terrible idea.
Alterother, Jul 01 2011
  

       A ten gram steel bullet cooled to absolute zero (this is impossible) and somehow fired from a gun with no friction heating in the barrel or intervening air (this is impossible) is capable of absorbing 1.5 kJ of energy from a human body at 37 deg C.   

       This is enough, if this bullet was embedded in the human torso (not surface contact as mentioned in the idea), and if the heat was pulled uniformly from human muscle tissue (this is impossible), to induce hypothermic temperatures(2 deg C decrease) in approximately .20 kg of human muscle tissue (It's surprisingly easy to find the specific heat of muscle tissue on line). Which would promptly warm back up due to the surrounding tissue.   

       What would really happen, if the bullet was heated minimally during firing/travel is a vanishingly small amount of frozen tissue right at the entry point or contact point if contact was made directly with skin. Followed by friction skin heating of the bullet sufficiently that it no longer chills the surrounding tissue. And not even that if any fabric or other insualtion/friction surface intervened. This amount of tissue would vanish in the otherwise damaged tissue from the impact/penetration.
MechE, Jul 01 2011
  

       If the bullet was still cold enough, it might feasibly cause a flash-freeze in the first, oh, half-millimeter of surrounding flesh. This would be similar to a third-degree burn, which does not hurt, removing some of the pain factor from the bullet's effect on the target.   

       Best-case scenario, you have just fired a marginally-less- effective bullet from an enormous, heavy gun that, at best, produces less than a quarter of the muzzle velocity of an equivalent-caliber firearm. Congradulations.
Alterother, Jul 01 2011
  

       But could you use it for cooling beer?
normzone, Jul 01 2011
  
      
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