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I was watching a TV show where a criminal used a bullet made out of blood, so that after entering the body the "evidence" (the bullet) melted away. I was wondering if it were possible to do something like that. That is, is it possible to make a bullet out of blood, ice, or a similar meltable substance that could be fired without melting and that would be capable of piercing a target and that would subsequently melt away? Any supporting physics/chemistry equations would be appreciated. Thanks in advance!

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    $\begingroup$ Actually, I'm pretty sure MythBusters did something on this.. The video *And yes, I'm aware that MythBusters are not always deemed a credible source. $\endgroup$ – CoilKid Jun 8 '15 at 23:23
  • $\begingroup$ better to use a crossbow with the arrows make of frozen water (it has the advantage of being more silent) $\endgroup$ – user66432 Jun 8 '15 at 23:37
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The reasons you are looking for (why it doesn't work) are twofold:

First, mass. Bullets are made out of lead, tungsten, depleted uranium etc. Heavy stuff. Aluminum and brass would make perfectly good ammunition if they weren't so light (or if the shootout was on the moon). The problem is lighter projectiles are greatly affected by air resistance and lose much of their accuracy and deliverable energy enroute to the target. The bullet is not so useful if it gets blown off course, or simply bounces off the target. Test this yourself - get a baseball, a baseball-sized ball of styrofoam, and a baseball-sized ball of lead. Have someone toss them from a 3rd-floor balcony and catch them bare-handed.

Second, heat. All that gunpowder igniting behind the bullet gets rather warm. And there's friction with the inside of the barrel. Plot that heat against the energy needed to boil 6 grams of water and we find that our ice projectile melts in the barrel, not in the target. And if it doesn't melt completely it certainly won't melt symmetrically, and a mis-shapen blob won't go where we want it to go.

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  • $\begingroup$ Musket balls tended to go where they were aimed. Unfortunately the barrow allowed for a fair amount of wiggle room. $\endgroup$ – LDC3 Jun 9 '15 at 3:14
  • $\begingroup$ Small point to add but lead is also soft and so is tungsten - pure Tungsten is very soft). Part of what makes guns accurate is after the firing, the gun's grooves cut into the bullet, setting it spinning which improves accuracy, similar to the feathers on an arrow. That only works with a soft metal. (Silver bullets wouldn't be accurate for very far cause Silver is too hard, but Gold would make great bullets) ;-) Ice also isn't easy to cut grooves into. Frozen blood - I'm not sure. I've never frozen my blood. But the melting would obviously be a problem. $\endgroup$ – userLTK Jun 9 '15 at 6:49
  • $\begingroup$ Hard metal projectiles can have driving bands made out of softer material. This is common on large-caliber field and naval guns. Ice is much softer than steel and would accept rifling easily, but once the outer layer melts the core won't spin all that fast. $\endgroup$ – paul Jun 9 '15 at 9:19
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Tricky with a typical explosive propelled bullet but if you have a compressed air gun handy then it's quite easy. It is even the subject of a long lived Urban Legend

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It's not feasible, this was tested by the MythBusters (assuming that a frozen blood bullet would be similar to an ice/meat one):

http://mythbustersresults.com/episode1

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  • $\begingroup$ Great, thanks for turning my comment into an answer. $\endgroup$ – CoilKid Jun 8 '15 at 23:27
  • $\begingroup$ Didn't realise you'd linked anything when I posted this. $\endgroup$ – Esteemator Jun 8 '15 at 23:28
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    $\begingroup$ Ah well, not a big deal :) $\endgroup$ – CoilKid Jun 9 '15 at 1:33

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