How is it that a bullet that is 12.7 mm in diameter can kill somebody with so much more bodily damage than a 20mm rebar rod that is impaled through the body? I see stories of people surviving impalement all the time, but a shot with a .50 cal to the same area almost always results in instant death. Shouldnt the bullet just go through its target because it travels so fast?
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When a bullet enters the body, particularly military rounds, it creates a cavity (cavitation), basically a giant hole, on the inside.
This pocket is pretty much a vacuum and as such it creates a massive negative pressure because of how fast it forms. What follows is a mini explosion that begins with an implosion of the tissue followed by a massive forced expansion. Think of a balloon squishing till it bursts and the air shooting out in all directions with a pop.
All of that happens INSIDE YOU. That’s not even talking about the fact that it also expands inside you and potentially splits through organs, veins, and whatever else.
A rebar is essentially just going to push tissue out of the way or split it like a knife. It’s not particularly aerodynamic so it doesn’t reach the speeds necessary to cause cavitation. So it pretty much makes a straight hole through you.
Depending on where it hit then, it could kill you or it could not. But it has a drastically lower area/volume that it takes out of the body and thus less of a chance of hitting anything vital.
I’ll look for a video of cavitation… there’s some pretty scary ones with clear ballistic gel that show it. Literally flashes like an explosion.
Here you go: https://youtu.be/fX4ODh1g4eM?t=62s
That video is just with a M855A1 round which is a .556 cartridge. Now look at the size difference between that and a 50bmg: https://qph.cf2.quoracdn.net/main-qimg-3c28291060d552b8c78222580350b19a.webp
Your example of 50bmg is particularly crazy too, because it is made for anti-materiel (not a typo, it means it goes through tanks and armored vehicles). It was made to shoot through fucking tanks. It does not leave much of a person left in its path. It’s fired by machine guns and heavy sniper rifles and is fucking massive.
you ever seen [a slo-mo of a 9mm going thru a ballistic dummy?](https://www.youtube.com/watch/okuoN3c_hW0)
imagine that from a giant ass anti material round and comparing it to simply being stabbed by a rebar rod and you’ll get the idea
As an experiment, fill a ziploc bag with water and stab it with a pencil.
If you leave the pencil in, it trickles. If you pull the pencil out, it drains.
Then fill another ziploc bag and shoot it with a gun.
Bullets have a massive amount of energy due to speed akd rotation, and exit wounds are much larger than entry wounds. If they aren’t immediately fatal, you’ll often die from organ failure or blood loss due to the damage caused.
Rebar is going much slower, and is generally a clean stab through and through. Much smaller wound, and kept in place acts as a plug preventing excess bleeding and organ damage.
Because air has mass and the slug momentum P=MV. It’s about the total energy transferred. The kinetic energy has to go somewhere.
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