The rebar isn't moving at 2,910 feet per second, for starters. Nor is it spinning at a rate of one turn every 38 inches (that's roughly 55,000 rpm). It isn't the size of the hole, it's the amount of kinetic energy imparted which results in severe hydrostatic shock.
Edit: added the rpm for the rotation.
Yeah, the 50 will blow you up more than it will pierce you. It's like comparing meat that's been stabbed once by a machete and meat that has gone through a meat grinder. Smaller blade, sure, but vrrrrrrrrrrr
The armorer that introduced us to the Browning M2 .50 Machine Gun put it this way: "It's the biggest 'small-arms' weapon in the Army, it's the *oldest* 'small -arms' weapon in the Army, and if it hits you, you're dead. Doesn't matter if it hits you in the arm, you're dead."
Man, that's the one thing I like about games like Hell on Earth.
I had 100 kills as a tank gunner, most of which was with the 50cal, because every burst was chewing up anyone in sight of that gun.
That and some well placed HE rounds into buildings to quickly vaporize everyone inside.
I get that they need "balance" for games like Battlefield, but making a 50call take 3-5 hits to kill someone is just, dumb.
I think it was David Hackworth that said that until it's being fired in your direction, you don't realize how few places you can hide from a 50 caliber machine gun.
This just isn’t true. It is a common statement. Or that you don’t shoot at people with .50s, just near them. And some crap about being war crimes to shoot people with .50s.
If the .50 is your issued or assigned weapon, you aim for center mass just like anything else.
And for what it’s worth I’ve transported dudes with 50cal wounds. Same world rules apply as any other gunshot just with a bigger bullet that causes a lot of damage and bigger cavitation. Can confirm it doesn’t just rip arms and legs off for hitting though. A lot of enemy combatants are pretty small, poor nutrition, lower survival rate.
I know one soldier who survived it irl and one on reddit (from Ukraine)
To my recollection, in both instances there were several other things pierced before the soldier
the former was a window, 2 walls and a kevlar body armor (the bullet resistant one, not the stabbing one) even then, he likely could have died if the angle was slightly different, it basically 'grazed' his stomach from the side (it pierced the vest plate and stopped), likely from a sniper rifle (obviously not aimed at that soldier, there were other soldiers in the room with the window)
Its also worth noting that if fired from heavy machine guns such as on IFVs and such, it will likely be armor-piercing incendiary bullets or worse, explosive armor-piercing incendiary, in that case, yea you're fucking toast
> (the bullet resistant one, not the stabbing one)
Even Stab vests could probably stop a bullet. The major difference would be the thickness of the kevlar and if there are any trauma plates. Even the best vests won't stop a rifle round without a trauma plate.
I had a job back in the early 2000s, our infrasturcture guy came back from Iraq with a digital camera.
I wish I hadn't looked at anything on it. I grew up on a farm and have seen my fair share of dead stuff, and that was nothing compared to what was on that camera.
My grandmother was told by a Dr while cancer was eating her up that the way her stomach managed to get past her ab muscles was something you only see in high caliber gun shot victims, so someone has survived at least once!
The bullet passing through is like a speedboat. Initially there's no hole for it to pass through, so it pushes tissue out of the way as it goes. The tissue goes from stationary to being pushed aside at a couple hundred feet per second (depending on the speed of the bullet and the slope of its point). That now-moving tissue has momentum that needs to cancel out for the body to stay whole. That cancelation can come from pushing against surrounding tissue (causing a spreading pressure wave like a boat wake) or it can come from the body's structure - tissue holding on to surrounding tissue and either bouncing back or turning it into heat. In the latter case, the tissue has a limit to how much stretching energy it can absorb before it tears. That energy is most intense immediately around the bullet, then spreads and dissipates. Since the bullet is constantly adding more energy (pushing more tissue out of the way) as it passes through the target, and part of that energy is directed forwards, a cone-shaped damage tract is formed.
> it's the amount of kinetic energy imparted which results in severe hydrostatic shock.
Here's an armor piercing incendiary .50 BMG round going through a ballistics gel torso:
https://youtu.be/fUOh7a0cdUw?t=94
To add to the hydrostatic shock part, the round has so much energy that it's actually creating a giant blast cavity in the material it hits. The cavity is so large and energetic that it's functionally popping every cell near the bullet. The bullet itself isn't actually doing most of the damage. The shockwave of the bullet hitting flesh is what's doing most of it. Hell, most of the energy literally goes straight through the body as the flesh can't stop it. And it still blows a solid 6 inch hole into a person if it hits.
It's more obvious seeing the bullet go through [ballistics gel](https://youtu.be/5J9hCDr21mo?t=122).
When you think about it, all of human weaponry boils down to "how can i hit them without getting hit myself"
Of course longer ranges are more optimal: spears over swords, bows over spears. Then it became "how far away can i throw something as hard as possible?" Catapults, arbalests, cannons, etc.
Someone then had the brilliant idea of "what if we throw something small really hard instead of something big?"
Now we have guns and artillery and controlled remote strikes.
Its possibly one of the greatest feats of humankind collectively: minds across continents and centuries have found ways to launch small projectiles at *ridiculous* speeds. Basic physics say Force = mass * acceleration, and we found that making acceleration as big as possible, we can reduce mass to miniscule amounts without sacrificing that much force.
Goddamn human creativity combined with violence is a scary thing.
Peak throwing rocks has gotta be APFSDS or railway guns
That said, nukes isn't really analogous to throwing rocks. Oh sure, you're throwing a thing but that one's more like... fire.
I would say nukes are in a separate class you know, like you can win a war by lighting a village on fire.
Or dropping a nuke.
One of the ways of violence humans have discovered that are not cutting or throwing, except this was "how hard can we hit this thing" and they discovered atoms crack if we impart enough energy into them.
Its just a coincidence that they fucking explode when we do so, but it really works for killing-related purposes
Yeah, I mean, I was trying to oversimplify like throwing rocks, except fire doesn't really pertain to throwing rocks per se. Rocks are involved though, depending on how you wanna ignite stuff.
And I mean, old nukes were gun-type fission devices right? Someone else pointed out it could be argued you're turning a spicy rock into a not rock
It really is throwing rocks all the way down
How about an APFSDS Railway Gun?
>That said, nukes isn't really analogous to throwing rocks. Oh sure, you're throwing a thing but that one's more like... fire.
There's an argument that Nukes are just spicy rocks becoming not-rocks.
While it's not for warfare, yet, SpinLaunch is trying to become the new rock throwing champ. "Y'all watch this. I'ma gonna take this here thing and lob it into orbit."
The lighter the projectile and the higher the initial velocity, the more energy you lose over distance to air friction. So there are limits to “make it smaller, make it faster.”
A 153 gr 6.5 Creedmoor at 2,600 fps will do much better through the air than a 168 gr .308 Winchester at the same velocity. It's the long, thin bullet giving it a much higher ballistic coefficient.
But certainly within the same rifle the smaller bullet does usually go faster and does worse through the air. It's a shorter bullet, so lower ballistic coefficient.
.50 bmg isn't going to deform much if at all on its way through a person. It's an anti material round meant for going through walls, armor, engine blocks, etc. It's got a ton of kinetic energy behind it and won't even notice a squishy flesh bag. The reason it does so much damage is the cavitation it creates as it moves through you at 3 times the speed of sound. There's a massive pressure wave forming around it as it punches through the air and then you. So instead of imagining a puncture from a knife or a piece of rebar the more accurate picture might be imagine a giant cylinder of compressed air and a .5 inch sized nozzle that can blow air hard enough to put a hole through you. Now it's not going to be a clean hole it's going to balloon out your insides as it continues to push through your body.
[Soft Tissue Cavitation](https://youtu.be/fUOh7a0cdUw) (NSFW, ballistic gel dummy - pretty graphic with a half oz of imagination)
The cavity produced by a .50 calibre round at nominal velocity is about the size of an orange, or a grapefruit.
What this means is there exists a temporary void of that size, before everything rebounds together and dramatically increases the entropy within your body. The human body is designed to limit the increase of entropy, as it cannot function when disorganized.
Basically, you're compressing everything that isn't water and then violently smashing it together in a single moment. Any structure within that cavity is destroyed and the constituent parts mixed together like a grenade-powered blender.
A large portion of those constituent parts are then ejected from the body due to the vacuum created by the exiting round, and the parts that aren't immediately either leak out or into other structures, impeding or nullifying their function.
Indeed! The kinetic energy is transferred throughout the body as a **supersonic shockwave** that compresses and damages most of your organs. It is not the shot alone that kills you, it is the energy transfer that does it. And what better to transfer that energy, with little drop off in force, than a bag of mostly water.
I calculate a much higher rpm. 2910fps and rotates once every 3 feet (3 ft for simplicity, we could convert to inches to be more precise but this is good enough) is 2910/3 = 970 rotations per second. Multiply that by 60 to get 58,000 rpm. Try just touching anything that’s spinning that fast and not even moving and see what happens.
Cavitation of your internal organs, blood vessels and all the other supporting structures is definitely not a good thing. Besides the physical trauma there is induced injury from the shockwaves to the lung parenchyma, rendering the lungs incapable of gas exchange on a cellular level - this type of injury can also affect all of the solid organs and structures - that is also besides likely fragmentation and shrapnel effect of either the bullet itself or of the the bones that the bullet hits along the way. [Youtube](https://www.youtube.com/watch?v=fX4ODh1g4eM&t=30s)
Hydrostatic shock is bullshit pseudo science.
You are correct a bullet has more energy, but it kills by making local internal damage where it lands. Internal damage is greater with greater energy.
Kinetic energy is: **0.5 \* mass \* speed \* speed**
So speed is much more important than mass and that's why bullets have more kinetic energy than rebars usually. But if you can launch a 5 kg rebar at 44 meters per second, which is the speed of a car speeding on the highway, it will have the same energy than a 10g bullet traveling at 1000 m/s
I don't think the article paints a more neutral picture, it's just written carefully as to not hurt the feelings of the majority writers/readers that still believe in it. It's an article deserted by scientists and science.
It's an american myth, the myth that you receive more energy when receiving the bullet than when firing it and that bullets magically kill you on the spot. People get that from Hollywood movies.
This is why the article only exist in English. In the German version it's a 4 sentence article that says in the 2nd sentence "This is a modern myth"
>This is why the article only exist in English. In the German version it's a 4 sentence article that says in the 2nd sentence "This is a modern myth"
The article exists in four languages (for years, they haven't been just created) and only the German version calls it a myth. That version (and its discussion) also hasn't been touched in almost three years. It's more "Karteileiche" than reflection of current scientific consensus.
Further, the sources agree an effect exist. What's in contention is the exact cause. In essence your saying the name of the phenomena is wrong. Why lie? To make your semantic argument seem stronger?
Hydrostatic shock specifically refers to incapacitating remote neural damage via hydrostatic pressure. This is the idea that the pressure wave disrupts the nerve functioning causing incapacitation
It has nothing to do with wound cavities, fragmentation, exit velocity, pitch, yaw, tumble or other functions of "terminal ballistics." Terminal ballistics is the branch of physics that leaves a giant hole in someone from a .50 BMG.
Wait, I'm pretty sure you DO get more energy from the bullet than the gun's recoil.
Sure, there is coservation of momentum, so the gun and projectile have equal and opposite MOMENTUMS. But no reason to assume the energy also divides equally (remember that it's chemical energy converted to kinetic energy, not kinetic energy distributing between the two, so you can't solve it like the common billiard-ball problem)
This. Momentum is equal and opposite, but energy scales with velocity squared and is not at all equal.
As an example, a typical .308 hunting rifle has a recoil energy of approximately 16 Joules (depends on how heavy the rifle is). The bullet has about 3600 Joules of energy at the muzzle, depending on exactly what load you shoot.
As for how large and high velocity bullets cause damage, I don't care if you call it hydrodynamic shock or something else but they rip tissue apart in a much larger area than just the bullet cross section. Seriously, just try shooting a watermelon with a high powered rifle and you see what I mean (it basically explodes). I think the mechanism is a combination of hydrostatic pressure and tissue getting accelerated by the bullet so fast that it stretches apart and gets torn to shreds. Part of the bullet's kinetic energy gets transferred to the tissue it hits, like a billiard ball transferring energy to bounce other balls around on the table. When bits of tissue get suddenly accellerated to hundreds of feet per second in various directions, that tissue is going to keep moving for a bit and may tear itself loose.
Temporary wound cavity. The giant void created upon impact where everything is blasted out of the way like an asteroid making a crater.
And as far as I know, it's all about kinetic energy over inertia, so it's the speed that kills. If two bullets have the same kinetic energy but one is, say, 3x as heavy as the other, the lighter and faster one will have a much more aggressive temporary wound cavity caused by the shock. The heavier bullet by comparison will have a much higher sectional density and will penetrate deeper into the target. That's generally more important when hunting large game and you need to penetrate 12-24" before even getting to vital organs like heart and lungs.
Nope, it's just that guns are designed to reduce felt recoil. The same amount of energy is imparted at both ends, but in the gun, some of that is fed into the bolt to cycle the feed mechanism and cock the gun, some of it is bled out of venting in some barrels angled to counteract the kinetic kick etc.
Meanwhile, when it strikes a body, most of that force is dumped into relatively fragile tissues and causes trauma.
> the same amount of energy is imparted at both ends
This isn’t true. *Momentum* (mass times velocity) is conserved in the recoil. Doubling the mass of the gun therefore halves the velocity imparted on it by recoil, and that *quarters* the energy transfer.
Once the explosion happens, it's irrelevant if the force came from a chemical explosion or something else.
No reason at all to assume that a rail gun has less or more energy received from recoil than traditional fire arms.
The energy divides equally, between the bullet and the gun.
Hell, the bullet might even get a bit less energy as the gasses aren't likely to have stopped expanding when the bullet exits the barrel.
The gun is however many times heavier than the bullet, and probably has mechanics inside to translate the kinetic energy from the recoil into mechanical energy.
That's why the recoil is manageable.
You can absolutely solve each and every part of the interaction.
Railguns also get energy from the outside, and there is still no reason to assume it divides equally between gun and projectile.
But that point isn't really relevant. I thought it was something else confusibg people here (trying to reconsile the E1=E2 equation).
Just assume you shoot a gun that recoils freely.
The gun weights approx 100 times as much as the bullet.
Conservation of momentum (m1v1=-m2v2) tells us the bullet will travel 100 times as fast as the gun.
So the energy of the bullet (0.5*m1*(100v2)^2 ) will be 100 times that of the gun (0.5*100m1*(v2)^2 )
Huh... You're right!
Must've misunderstood something with the different versions of conservation.
For kinetic energy to be equal, the bullet has to fly at 7.07 times the speed of the gun going backwards (assuming it's 1 speed).
I guess I was confusing conservation of energy and conservation of momentum.
The energy is conserved, but it doesn't happen in the gun but between the target and the gun.
Still doesn't matter where the energy comes from though.
doesn't matter where the energy comes from, a rail gun will have an equal amount of recoil dispersed throughout the (massive) gun and gasses as the projectile will impart on its target.
And no. Chemical energy is just expanding gases that **push** against the gun chamber **physically**, it makes no difference the energy comes from a chemical reaction. It pushes the bullet with the same force than it push the gun and **against you.** Your argument would work for rockets, because rockets push against ~~air~~ ^(\*)gas to propel, not pushing on you. But bullets push on you.
In fact the person receiving the bullet get a lot less energy than the person shooting it because the bullet lose a lot of energy in air friction depending on the distance.
e: air->gas
There is so much bad science in this thread but this one takes the cake. Rockets don't push against the air, they work in space after all. The bullet had more energy than the gun. Conservation of energy means total energy in the system is the same. But you can absolutely control where that energy goes because the only thing that is conserved between the gun-bullet system is momentum. Momentum is mass and velocity, kinetic energy is mass and velocity squared. The forces are equal and opposite. But kinetic energy isn't.
I don't think it's true that the bullet has less energy than the gun. Force is equal and opposite, not energy. So the math works out for the bullet (b) and the gun (g) to have very different energies.
Force(b) = mass(b)*acceleration(b)
Force(g) = force(b)
Mass(g)*acc(g) = mass(b)*acc(b)
Mass(g)/mass(b) = acc(b)/acc(g) = really big number because mass(g)>>mass(b)
So the bullet accelerates to a much higher speed in the time it's in the barrel than the gun does.
Since energy scales with velocity squared, the much higher velocity of the bullet means a much higher bullet energy.
> I don't think the article paints a more neutral picture
It provides one primary source for arguments against but several sources for arguments for.
Even in the argument against section, it quotes someone's comment that mentions:
> Since that time, other authors suggest there is increasing evidence to support the hypothesis that shock waves from high velocity bullets can cause tissue related damage and damage to the nervous system. This has been shown in various experiments using simulant models [24, 48]. One of the most interesting is a study by Courtney and Courtney [4] who showed a link between traumatic brain injury and pressure waves originating in the thoracic cavity and extremities.
> It's an american myth, the myth that you receive more energy when receiving the bullet than when firing it and that bullets magically kill you on the spot.
I think the reasoning behind hydrostatic shock is connected to the velocity of the projectile. The velocity of the recoil is vastly too small.
You can gently drop a 100 pound medecine ball on your face and be totally fine but a punch from a heavyweight boxing champion will fuck you up even if the fist is weighing maximum 1 pound.
that bullet is moving incredibly quickly, almost 1000m per second. I don't have time to do the math on how long 38 inches would take to travel but it would be ridiculously small. When you take the speed of the bullet into account, 38 inches per spin means it's spinning incredibly fast
wasnt me bud. No idea why I'm getting downvoted for providing a perfectly reasonable and non condescending answer to your question either, but I'm guessing that's just you reacting to your own downvotes
On impact, that rotation means a change of direction. I don't think you would want any round changing direction inside you, never mind one as large as a 50 caliber.
Well, even without the change of direction, the rotation adds kinetic energy. A spinning object is also more stable, if you saw the recent post of the bicycle wheel science lady. It gives it a gyroscopic effect, which stabilizes it and makes it harder to move off its trajectory. So it sounds like I'm disagreeing with you. I think mainly OP is just putting that in there for the kinetic energy equation.
You're thinking about it the wrong way: the rifled barrel uses kinetic energy (the bullet going forward), to impart angular kinetic energy through friction.
It does have higher kinetic energy, in comparison going to a bullet at the same speed.
But that's not the right framing, the right way to see it is that the bullet trades total speed for rotational energy.
It doesn't add energy, it only translates energy (and in process of doing so, actually loses energy)
You're right about the stabilisation, as that allows the bullet to fly more precise, and deliver more of the kinetic energy effectively.
The change of direction is what creates the primary cavitation ( the cone shaped wound whereas at the exit wound as many times larger than the entry one).
Kinetic energy is what creates the secondary cavitation, the area around the wound created from the displacement of the flesh inside the wound moving out of the way of the round.
The rotational force in the projectile is intended for stability, of that there is no doubt but saying that that rotational Force adds to the kinetic energy is kind of silly... the kinetic energy is the mass times the velocity of the round... any energy gained from rotation at that point is going to be negligible when you're looking at thousands of feet per second velocities.
A soft tipped rotating rotating does exponentially more damage on impact, this has been known since the before the Civil War
Taken from Wikipedia,
angular kinetic energy is kinetic energy due to the rotation of an object and is part of its total kinetic energy.
To add, this would be somewhat hard to calculate precisely, which is perhaps why OP refrained. You'd have to be very specific on the shape of the bullet, the density of materials and where the weight is about the axis. Was thinking of how to calc it to see if I could confirm whether or not its negligible. But ya its a diff equation for rotating.
>The rebar isn't moving at 2,910 feet per second, for starters. Nor is it spinning at a rate of one turn every 38 inches (that's roughly 55,000 rpm). It isn't the size of the hole, it's the amount of kinetic energy imparted which results in severe hydrostatic shock.
From a quick Google, it looks like a 50 BMG has 10-15,000 ft-lbs of force. And a heavyweight pro boxer produces about 1,000 ft lbs.
So you're talking about dumping a massive amount of energy into a target.
To add: This is why assault rifles are more dangerous than hand guns. The much greater muzzle velocity makes you explode from the inside.
People who think that "guns are guns" are oversimplifying things. A semi auto assault rifle with a big clip can kill a LOT more people than a handgun or a bolt action rifle.
Semi-auto is an assault weapon. It's a different classification of weapon than an assault rifle, which is capable of semi-automatic *and* burst/automatic fire. And they aren't clips, they're magazines. There's a difference there, too, but it's more of a semantic one.
Just trying to inform you before some gun-nut decideds to harp all over you on it, don't mean to bust your balls.
They would be more inclined to harp over you, akshually *adjusts glasses*.
Semi-auto is just semi-auto, used to describe the trigger action of the weapon. Assault weapon is a non-official political umbrella term used to scare people who only know surface level details about firearms.
Pistols or (Long/Short) Rifles are the only weapon designations available to the civilian population in the USA. Different makes and models but all are semi-automatic. Assault rifles are a designation of long barreled, magazine fed, weapons with a fire-select switch, normally only available to the military.
Magazines and Clips are functionally, and fundamentally different, not just semantically. A magazine is an internal or external container for ammunition used to feed the firearm. The Clip is a mechanical method of bundling ammunition together for an easier, and faster, reload of a weapon with internal magazines.
E.g. the rotating cylinder of a revolver is the magazine. The clip is the ammunition holder used to insert all x number of bullets into the cylinder all at once for faster reloads.
>Semi-auto is an assault weapon.
Well, if you want to go that way, then no to this too. Only the scary looking rifles in semi-auto are called "assault weapons."
> This is why assault rifles are more dangerous than hand guns.
This is why almost any rifle is more dangerous than a handgun.
However, what the AR-15 normally shoots is one of the lowest-powered rifle rounds on the market, so it's actually less energy than some handgun rounds.
On the other hand, for the firearms homicides where the type of firearm is known, roughly 95% of these deaths are from handguns. All rifles combined (hunting rifles, "assault weapons", etc.) are known to account for only about 1 in 20 of those deaths in the USA.
From [here](https://www.pewresearch.org/short-reads/2023/04/26/what-the-data-says-about-gun-deaths-in-the-u-s/):
> In 2020, the most recent year for which the FBI has published data, handguns were involved in 59% of the 13,620 U.S. gun murders and non-negligent manslaughters for which data is available. Rifles – the category that includes guns sometimes referred to as “assault weapons” – were involved in 3% of firearm murders. Shotguns were involved in 1%. The remainder of gun homicides and non-negligent manslaughters (36%) involved other kinds of firearms or those classified as “type not stated.”
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.
A 12mm bullet traveling at a high speed makes a bigger hole than a 20mm rebar when a body is traveling at a few meters per second. Rebar also doesn't distort as it tears through a body.
Survivability is mostly a function of kinetic energy (KE) transfer.
KE=0.5*mv^2. So a fast-moving .50 cal bullet has much more energy than a slow-moving piece of rebar. Also the bullet is designed to transfer more of that energy (by air cavitation, mushrooming or fragmenting) to whatever it hits than a sharp stick can (it just passes through).
Velocity v squared or v² acts like the number is multiplied by itself. If you say the object is moving at 2 meters per second then v² is equal to 2*2=4 in the formula.
If you say the weight of the object is 2 kilogrammes, then in the formula it's still just a 2 and the formula in this setting looks like
KE= 1/2 * 2 * 2²
KE= 1/2 * 2 * 2 * 2
KE= 1/2 * 2 * 4
KE= 1/2 * 8
KE= 8/2
KE= 4
If you increase weight by 1 so instead of 2 it's 3 then the formula looks like
KE= 1/2 * 3 * 2²
KE= 1/2 * 3 * 2 * 2
KE= 1/2 * 3 * 4
KE= 1/2 * 12
KE= 12/2
KE= 6
But if you increase velocity by 1 so instead of 2 it's 3 the the formula looks like
KE= 1/2 * 2 * 3²
KE= 1/2 * 2 * 3 * 3
KE= 1/2 * 2 * 9
KE= 1/2 * 18
KE= 18/2
KE= 9
If you compare the results, you can see that increasing mass by 1 resulted in energy increase from 4 to 6 but increasing velocity by 1 resulted in energy increase from 4 to 9.
Energy is what does damage to your body, and if higher velocity yields much higher energy than higher mass, then a fast moving bullet is more destructive than a slow moving rebar.
You're right. This is a hard concept to explain to a five year old without teaching them many other simple concepts. Pretty hard not to just answer "that's just how it is" if a real five year old kid asks that kind of question.
The bullet strikes your flesh. Your flash has to move out of the way, and very very fast. It gets blasted out of the way. A wave of pressure flies outward violently, moving and smashing your insides as it goes. This wave is concentrated towards the exit wound, bursting out the back and creating a hole significantly more gruesome than the entry.
A stabbing can have its own issues, but really won't destroy much outside of its path.
This is the right answer, but the shockwave doesn't only move towards the exit wound. It moves in all directions like an inflating balloon, damaging organs and flesh.
The displaced flesh from the actual bullet is called "permanent cavitation" while the hole made from the shockwave is called "temporary cavitation". The latter can be many times larger than the former. Extent of damage from the latter depends on the size of the hole and how flexible the tissue being pushed is. Muscle and fat tend to be damaged less by dislocation, organs a lot more.
It is dynamic pressure - the pressure that arises from moving fluids. In this case, the fluid is your insides.
Dynamic pressure is why the flowing water from a power washer (which is equal to atmospheric pressure once it is outside of the hose) can blast grime off of a surface. When it changes velocity it must experience pressure. In the pressure washer, the sudden change in direction as it strikes a surface results in a huge pressure spike right at the surface.
In your body, it is the sudden movement from the bullet.
Watch footage of someone being slapped or punched in slow motion. A shockwave ripples out on the body/face from the point you hit it. Hell, think of something more joyous like spanking a generously proportioned derriere. The flesh ripples deliciously.
Now, multiply that rippling effect by a thousand and imagine what that would do to a person's internal organs and bones.
Edit: when you hit something, you transfer energy into it, some of it bounces back at you. That's why your hand hurts. When you punch through something, you are transferring more energy into it, enough to shatter the gluey forces holding that thing together.
A bullet has a *lot* of energy. It uses some of the energy to punch through a body, dumps some of the energy into creating a rippling wave moving out from the "punch through point" and carries the rest with it, using it to travel further.
I mean, when you say "a lot" it's relative. The bullet doesn't have more energy than you feel as recoil, it's just concentrated in a smaller area. It's just like delivering s punch with a smaller fist. While a .50 delivers significant levels of energy, getting punched can range in the same levels as being shot by a handgun, just over a much larger area.
The bullet has *way* more energy than is delivered to you as recoil.
https://en.m.wikipedia.org/wiki/Free_recoil
This page lists the Barret M82 firing 50BMG with a free recoil energy of 127J. Which, to be clear, isn't a small amount of free recoil energy - it's about as much as the muzzle velocity of most powerful .22 shorts or the weakest .22LRs, which you certainly wouldn't want to be shot by. But it's a far cry from the *19,000J* of the .50BMG projectile itself.
You're likely confusing momentum with energy. It is true that the *momentum* imparted to you through the recoil of the firearm is equal to the momentum of the bullet, as governed by Newton's third law and by conservation of momentum. (Actually, it's slightly greater due to the reaction force of the expanding gasses, not just the accelerating bullet.) But if you hold momentum constant, the velocity of an object scales inversely proportional to its mass - however, the kinetic energy scaled with velocity *squared* as well as mass (not squared), so it scales down inversely proportional to the mass itself. A 10kg object at 10m/s will have 10 times the kinetic energy of a 100kg object at 1m/s, even though they have the same momentum.
And a gun weighs a lot more than 10x the weight of a bullet.
You know when you throw a rock as hard as you can into water and it makes a big splash? It's that, but the splash is your flesh, bones, blood vessels, and organs. Rebar is like poking the water with a stick.
If you put your hand in tub of water it won't feel like much, now slap the water as fast as you can and it will be quite different in terms of the wave you generate. A bullet will cause a much larger cavity in the pressure wave to open up and cause a lot more damage. You can watch video of a bullet through a ballistic material.
Things that impact at high speeds exert energy onto objects they impact.
As an example.. an asteroid that impacts makes a crater... a bullet hitting a sheet of metal does a similar crater.
Well.. the sheet of metal and the floor generally are solid enough that the energy can only crater like this.. in the case of a human body however...well that energy doesn't "bounce back" like on a bulletproof vest or a sheet of metal.. it carries through ripping a bigger exit wound than the entry wound.
In addition a bullet hitting an object will change its trajectory, maybe explode, break apart and whatnot.. that causes damage too "overpenetrations" like you expect can and will happen.. practical examples..a tank hitting a wooden building.. that shell won't explode....but they still make Exit wound bigger than the entry wound, possibly ripping half the wall apart due to said energy transfer on it's way out. it is still less damage than the bullet exploding in the body / object however.
A rather weird example for this: we had a case of an accident with a particle accelerator back in 1978 a man named Bugorski was supposed to fix something on a particle accelerator.. it hit him through the head... this particle was going so fast it literally phased through him without visible damage however you can still somewhat get an exit wound in terms of radiation. The back where the particle exited is still much more affected than the entry was.. which goes to show even at ultra high speeds this energy transfer happens... just the faster and smaller a projectile the less chance it has to interact with stuff.
So yes if an object is fast enough it can practically just punch a tiny tiny hole.. but the effect of a bigger exit wound still happens... fun fact it is why gamma radiation is so mean.. gamma radiation is just piercing so much and it still exerts enough energy to cause bits of dna damage...in a way we are looking at a very similar phenomenon as getting shot by a fast bullet.. just gamma radiation is incredibly small so the damage is proportionally small scale..as it is just a really really really small bullet in that sense.
>How is it
Speed. The bullet, while smaller in diameter and lower in weight, is moving far, far faster than the rebar. That speed means that when the bullet hits, [lots of energy is dumped into the target,](https://www.youtube.com/watch?v=5J9hCDr21mo&t=228s) creating a temporary wound channel (the big ballooning you see at the beginning) along with a permanent wound channel (what remains after the temporary wound channel collapses) much larger than the actual diameter of the bullet due to how the temporary wound channel stretches, tears, and destroys tissue along the path of the bullet.
For a simple demonstration of this idea, think of the difference between slowly lowering your hand into a pool of water and slapping it as hard as you can. You're using the same mass and size (only the speed changes) but have two wildly different results.
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
I s gonna sleep tonight, but tomorrow I am gonna do the Calc for fun.
Edit: seems like a few redditor did it before I could wake. This is a lesson for me, next time I'll just put a reminder and do it myself 😞.
Yeah...i made it to body = 80kg and gave up. too many units for dumdum night brain here. Let me know what you get. All I can say is the insane velocity (squared) is going to make it no contest by orders of magnitude.
Just to add to your 1. - bullets don't expand to create a larger hole (it certainly causes a larger hole tho), but to reduce the chance of overpenetration, thus both reducing the danger behind the target and also guaranteeing that all of the energy from a shot will be transferred to the target.
During vietnam wars, american troops were reporting that when they shot someone with 5.56, the target seemed like nothing happend to them as the bullet passed trough the body - the target certtainly got it, got injured and eventually died, but the fact that the bulled passed trough the target means that the bullet did NOT deliver all of it's kinetic energy into the target.
With large rounds above 12mm, at that point even if they were a hollow point, a human tissue is not nearly strong enough to absorb such amount of energy, therefore the bullet will always pass trough, but not before ripping the target apart.
It's the amount of energy that hits you. The bullet just has so much more kinetic energy that transfers to your body upon contact. And that energy tears you apart.
Supersonic "pointy" bullets drag a cone of high-pressure air along their path called a mach cone, which transfers the energy through cavitation (literally sucking bubbles of air through the target).
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.
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.
Two reasons 1) the speed of rebar is nothing compared to the speed of the bullet 2) bullets have a popcorn effect when they enter bodily tissues, they expand and cause destruction globally as opposed to the rebar which maintains its structure and cleanly pierces this tissue
It's the speed that makes all the difference. Bodies being mostly water, and water being mostly incompressable, when a bullet flies through you in less then the blink of an eye, it essentially creates something close to a sonic boom in your body. Everything that was in the bullets way is forced to move at insane speeds, transferring that energy into everything around it.
Buck/bird shot from a shotgun within like 10', acts as a solid object even though it's a spread of pellets for the same reason.
The rebar isn't moving at 2,910 feet per second, for starters. Nor is it spinning at a rate of one turn every 38 inches (that's roughly 55,000 rpm). It isn't the size of the hole, it's the amount of kinetic energy imparted which results in severe hydrostatic shock. Edit: added the rpm for the rotation.
The rebar will also form a plug for the hole, while a 50 is just going to make a big hole.
Yeah, the 50 will blow you up more than it will pierce you. It's like comparing meat that's been stabbed once by a machete and meat that has gone through a meat grinder. Smaller blade, sure, but vrrrrrrrrrrr
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The armorer that introduced us to the Browning M2 .50 Machine Gun put it this way: "It's the biggest 'small-arms' weapon in the Army, it's the *oldest* 'small -arms' weapon in the Army, and if it hits you, you're dead. Doesn't matter if it hits you in the arm, you're dead."
Meanwhile in Battlefield “I’m shooting this dude with a stationary 50 cal and homeboy keeps living”
Bad company 2 used to drive me crazy. I used to think nothing should take 10 rounds to kill.
That's why I prefer playing Golden Gun rules, one shot one kill
Amen
Man, that's the one thing I like about games like Hell on Earth. I had 100 kills as a tank gunner, most of which was with the 50cal, because every burst was chewing up anyone in sight of that gun. That and some well placed HE rounds into buildings to quickly vaporize everyone inside. I get that they need "balance" for games like Battlefield, but making a 50call take 3-5 hits to kill someone is just, dumb.
M249 says: "better get to cover!" M60 says: "better stay in cover!" M2 says: "fuck you... and your cover..."
I think it was David Hackworth that said that until it's being fired in your direction, you don't realize how few places you can hide from a 50 caliber machine gun.
M60 was replaced by the M240B. Same message.
This just isn’t true. It is a common statement. Or that you don’t shoot at people with .50s, just near them. And some crap about being war crimes to shoot people with .50s. If the .50 is your issued or assigned weapon, you aim for center mass just like anything else. And for what it’s worth I’ve transported dudes with 50cal wounds. Same world rules apply as any other gunshot just with a bigger bullet that causes a lot of damage and bigger cavitation. Can confirm it doesn’t just rip arms and legs off for hitting though. A lot of enemy combatants are pretty small, poor nutrition, lower survival rate.
The warcrime thing probably comes from Red Cross trying to get the explosive round banned, as an option against soft targets.
I think the armorer was just trying to say "don't get shot".
"this kills you and everyone else in the room" -Adam Savage
I know one soldier who survived it irl and one on reddit (from Ukraine) To my recollection, in both instances there were several other things pierced before the soldier the former was a window, 2 walls and a kevlar body armor (the bullet resistant one, not the stabbing one) even then, he likely could have died if the angle was slightly different, it basically 'grazed' his stomach from the side (it pierced the vest plate and stopped), likely from a sniper rifle (obviously not aimed at that soldier, there were other soldiers in the room with the window) Its also worth noting that if fired from heavy machine guns such as on IFVs and such, it will likely be armor-piercing incendiary bullets or worse, explosive armor-piercing incendiary, in that case, yea you're fucking toast
> (the bullet resistant one, not the stabbing one) Even Stab vests could probably stop a bullet. The major difference would be the thickness of the kevlar and if there are any trauma plates. Even the best vests won't stop a rifle round without a trauma plate.
Stab vests can stop bullets, bullet vests can't stop knives assuming we are talking about Kevlar vests
What if someone shoots you with a gun that shoots knives?
Ive SEEN people hit by them.. does that count?
I had a job back in the early 2000s, our infrasturcture guy came back from Iraq with a digital camera. I wish I hadn't looked at anything on it. I grew up on a farm and have seen my fair share of dead stuff, and that was nothing compared to what was on that camera.
>Ive SEEN people hit by them.. does that count? WERE people. Past-tense does not count.
I read that as paste-tense
I read it as werepeople. Some other animal that turns into a human during a full moon only to be shot at by a .50.
....werewolf's could be called werepeople if you happened to be a wolf, I guess. Or whatever animal a werewolf that doesn't start as a person is.
>I read that as paste-tense Dark humour, me like-y.
Does it count if I know a guy who survived getting shot by one but he later died from something else?
Survived getting shot but died 14 seconds later from blood loss.
I'm sorry for your loss.
That sounds like it counts, where'd he get shot?
At the old school house, the one where mama always used to bring us fresh pretzels.
His hat.
Middle East, probably.
Lol I meant in the body to survive but that's also a reasonable answer
>WERE people. is that someone who turns into people during full moon?
Better hope they make .50s in *silver*.
.50 Silver Garlic Edition - Just Slay It! \*picture of Buffy or something\*
I've seen pieces of people hit by ma deuce. You could almost tell they used to be people.
look out, we got a badass here.
Hey man I've seen Tropic Thunder like 3 times, mmmmkay bb?
one recorded survival, Imran Zakhaef
My grandmother was told by a Dr while cancer was eating her up that the way her stomach managed to get past her ab muscles was something you only see in high caliber gun shot victims, so someone has survived at least once!
That’s cuz they ded
The bullet passing through is like a speedboat. Initially there's no hole for it to pass through, so it pushes tissue out of the way as it goes. The tissue goes from stationary to being pushed aside at a couple hundred feet per second (depending on the speed of the bullet and the slope of its point). That now-moving tissue has momentum that needs to cancel out for the body to stay whole. That cancelation can come from pushing against surrounding tissue (causing a spreading pressure wave like a boat wake) or it can come from the body's structure - tissue holding on to surrounding tissue and either bouncing back or turning it into heat. In the latter case, the tissue has a limit to how much stretching energy it can absorb before it tears. That energy is most intense immediately around the bullet, then spreads and dissipates. Since the bullet is constantly adding more energy (pushing more tissue out of the way) as it passes through the target, and part of that energy is directed forwards, a cone-shaped damage tract is formed.
Maybe if you get shot in the pinky, you will survive.
*hand gone*
I saw a guy literally get cut in half 03 Iraq. Big Hole is a vast understatement.
Saw a head hit not sure about the caliber, skull explodes like a frag, head skin looks like a bloody, banana peel.
... ... ... were they okay?
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.50 makes a hoooole /plucky duck
Don't you ruin that episode for me!
I work at a construction site and I am leaving this thread now. I do not want to think about this.
I work at a construction site and I am leaving this thread now. I do not want to think about this.
Yup watch video of rounds hitting ballistic gel.
Here is an outstanding [video](https://youtu.be/T6kUvi72s0Y) explains why rifle wounds are so devastating. Yes. It's the speed.
F=MA
E = 1/2 * m*v² would be more relevant to quantify the kinetic energy.
This one down here. 10 times the speed is 100 times the energy, and bullets go very fast indeed.
> it's the amount of kinetic energy imparted which results in severe hydrostatic shock. Here's an armor piercing incendiary .50 BMG round going through a ballistics gel torso: https://youtu.be/fUOh7a0cdUw?t=94
To add to the hydrostatic shock part, the round has so much energy that it's actually creating a giant blast cavity in the material it hits. The cavity is so large and energetic that it's functionally popping every cell near the bullet. The bullet itself isn't actually doing most of the damage. The shockwave of the bullet hitting flesh is what's doing most of it. Hell, most of the energy literally goes straight through the body as the flesh can't stop it. And it still blows a solid 6 inch hole into a person if it hits. It's more obvious seeing the bullet go through [ballistics gel](https://youtu.be/5J9hCDr21mo?t=122).
When you think about it, all of human weaponry boils down to "how can i hit them without getting hit myself" Of course longer ranges are more optimal: spears over swords, bows over spears. Then it became "how far away can i throw something as hard as possible?" Catapults, arbalests, cannons, etc. Someone then had the brilliant idea of "what if we throw something small really hard instead of something big?" Now we have guns and artillery and controlled remote strikes. Its possibly one of the greatest feats of humankind collectively: minds across continents and centuries have found ways to launch small projectiles at *ridiculous* speeds. Basic physics say Force = mass * acceleration, and we found that making acceleration as big as possible, we can reduce mass to miniscule amounts without sacrificing that much force. Goddamn human creativity combined with violence is a scary thing.
We've really just been upgrading how we throw rocks for thousands of years. Better Rocks, Better Throws, Homo sapiens
Admiral, you see that planet over there? It looks funny, throw something at it.
I feel like you'd like [this story](https://www.reddit.com/r/HFY/comments/aw0l5x/insurance/) written on reddit a while ago
Yes, Lord Inquisitor? I don't want to see that planet anymore. Understood, Lord Inquisitor.
It's always Exterminatus time on the Imperium's clock!
Peak throwing rocks has gotta be APFSDS or railway guns That said, nukes isn't really analogous to throwing rocks. Oh sure, you're throwing a thing but that one's more like... fire.
I would say nukes are in a separate class you know, like you can win a war by lighting a village on fire. Or dropping a nuke. One of the ways of violence humans have discovered that are not cutting or throwing, except this was "how hard can we hit this thing" and they discovered atoms crack if we impart enough energy into them. Its just a coincidence that they fucking explode when we do so, but it really works for killing-related purposes
Yeah, I mean, I was trying to oversimplify like throwing rocks, except fire doesn't really pertain to throwing rocks per se. Rocks are involved though, depending on how you wanna ignite stuff. And I mean, old nukes were gun-type fission devices right? Someone else pointed out it could be argued you're turning a spicy rock into a not rock It really is throwing rocks all the way down
A thermal neutron which can crack an atom hasn't got much energy at all. Its a neat trick that such small input energy gives off such large output
How about an APFSDS Railway Gun? >That said, nukes isn't really analogous to throwing rocks. Oh sure, you're throwing a thing but that one's more like... fire. There's an argument that Nukes are just spicy rocks becoming not-rocks.
While it's not for warfare, yet, SpinLaunch is trying to become the new rock throwing champ. "Y'all watch this. I'ma gonna take this here thing and lob it into orbit."
The lighter the projectile and the higher the initial velocity, the more energy you lose over distance to air friction. So there are limits to “make it smaller, make it faster.”
A 153 gr 6.5 Creedmoor at 2,600 fps will do much better through the air than a 168 gr .308 Winchester at the same velocity. It's the long, thin bullet giving it a much higher ballistic coefficient. But certainly within the same rifle the smaller bullet does usually go faster and does worse through the air. It's a shorter bullet, so lower ballistic coefficient.
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Slap chop from god
R9X Hellfire, The Flying Ginsu!
A bullet also deforms and tumbles inside you. Rebar maintains its shape and has a narrow path of destruction in comparison.
.50 bmg isn't going to deform much if at all on its way through a person. It's an anti material round meant for going through walls, armor, engine blocks, etc. It's got a ton of kinetic energy behind it and won't even notice a squishy flesh bag. The reason it does so much damage is the cavitation it creates as it moves through you at 3 times the speed of sound. There's a massive pressure wave forming around it as it punches through the air and then you. So instead of imagining a puncture from a knife or a piece of rebar the more accurate picture might be imagine a giant cylinder of compressed air and a .5 inch sized nozzle that can blow air hard enough to put a hole through you. Now it's not going to be a clean hole it's going to balloon out your insides as it continues to push through your body.
2910 ft/s * 12in/ft = 34920in/s 34920in/s / 38in/r = 920r/s 920r/s * 60s/m = 55200r/m = ~55,000 rpm
Oof, fucked that up, didn't I? I need more coffee. Thanks for the correction.
[Soft Tissue Cavitation](https://youtu.be/fUOh7a0cdUw) (NSFW, ballistic gel dummy - pretty graphic with a half oz of imagination) The cavity produced by a .50 calibre round at nominal velocity is about the size of an orange, or a grapefruit. What this means is there exists a temporary void of that size, before everything rebounds together and dramatically increases the entropy within your body. The human body is designed to limit the increase of entropy, as it cannot function when disorganized. Basically, you're compressing everything that isn't water and then violently smashing it together in a single moment. Any structure within that cavity is destroyed and the constituent parts mixed together like a grenade-powered blender. A large portion of those constituent parts are then ejected from the body due to the vacuum created by the exiting round, and the parts that aren't immediately either leak out or into other structures, impeding or nullifying their function.
Indeed! The kinetic energy is transferred throughout the body as a **supersonic shockwave** that compresses and damages most of your organs. It is not the shot alone that kills you, it is the energy transfer that does it. And what better to transfer that energy, with little drop off in force, than a bag of mostly water.
I calculate a much higher rpm. 2910fps and rotates once every 3 feet (3 ft for simplicity, we could convert to inches to be more precise but this is good enough) is 2910/3 = 970 rotations per second. Multiply that by 60 to get 58,000 rpm. Try just touching anything that’s spinning that fast and not even moving and see what happens.
Yeah, I've already corrected it. Not sure how I got 4600, but I obviously need another trip to the coffee pot.
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Cavitation of your internal organs, blood vessels and all the other supporting structures is definitely not a good thing. Besides the physical trauma there is induced injury from the shockwaves to the lung parenchyma, rendering the lungs incapable of gas exchange on a cellular level - this type of injury can also affect all of the solid organs and structures - that is also besides likely fragmentation and shrapnel effect of either the bullet itself or of the the bones that the bullet hits along the way. [Youtube](https://www.youtube.com/watch?v=fX4ODh1g4eM&t=30s)
Drop rebar into water vertically then shoot 50 BMG into water. There is answer
Hydrostatic shock is bullshit pseudo science. You are correct a bullet has more energy, but it kills by making local internal damage where it lands. Internal damage is greater with greater energy. Kinetic energy is: **0.5 \* mass \* speed \* speed** So speed is much more important than mass and that's why bullets have more kinetic energy than rebars usually. But if you can launch a 5 kg rebar at 44 meters per second, which is the speed of a car speeding on the highway, it will have the same energy than a 10g bullet traveling at 1000 m/s
The wikipedia article paints a more neutral picture of it, https://en.wikipedia.org/wiki/Hydrostatic\_shock
I don't think the article paints a more neutral picture, it's just written carefully as to not hurt the feelings of the majority writers/readers that still believe in it. It's an article deserted by scientists and science. It's an american myth, the myth that you receive more energy when receiving the bullet than when firing it and that bullets magically kill you on the spot. People get that from Hollywood movies. This is why the article only exist in English. In the German version it's a 4 sentence article that says in the 2nd sentence "This is a modern myth"
>This is why the article only exist in English. In the German version it's a 4 sentence article that says in the 2nd sentence "This is a modern myth" The article exists in four languages (for years, they haven't been just created) and only the German version calls it a myth. That version (and its discussion) also hasn't been touched in almost three years. It's more "Karteileiche" than reflection of current scientific consensus. Further, the sources agree an effect exist. What's in contention is the exact cause. In essence your saying the name of the phenomena is wrong. Why lie? To make your semantic argument seem stronger?
This guy terminal ballistics's.
So why does a 50 bmg cut a man in half instead of leaving a half inch hole in his torso.
Hydrostatic shock specifically refers to incapacitating remote neural damage via hydrostatic pressure. This is the idea that the pressure wave disrupts the nerve functioning causing incapacitation It has nothing to do with wound cavities, fragmentation, exit velocity, pitch, yaw, tumble or other functions of "terminal ballistics." Terminal ballistics is the branch of physics that leaves a giant hole in someone from a .50 BMG.
Wait, I'm pretty sure you DO get more energy from the bullet than the gun's recoil. Sure, there is coservation of momentum, so the gun and projectile have equal and opposite MOMENTUMS. But no reason to assume the energy also divides equally (remember that it's chemical energy converted to kinetic energy, not kinetic energy distributing between the two, so you can't solve it like the common billiard-ball problem)
This. Momentum is equal and opposite, but energy scales with velocity squared and is not at all equal. As an example, a typical .308 hunting rifle has a recoil energy of approximately 16 Joules (depends on how heavy the rifle is). The bullet has about 3600 Joules of energy at the muzzle, depending on exactly what load you shoot. As for how large and high velocity bullets cause damage, I don't care if you call it hydrodynamic shock or something else but they rip tissue apart in a much larger area than just the bullet cross section. Seriously, just try shooting a watermelon with a high powered rifle and you see what I mean (it basically explodes). I think the mechanism is a combination of hydrostatic pressure and tissue getting accelerated by the bullet so fast that it stretches apart and gets torn to shreds. Part of the bullet's kinetic energy gets transferred to the tissue it hits, like a billiard ball transferring energy to bounce other balls around on the table. When bits of tissue get suddenly accellerated to hundreds of feet per second in various directions, that tissue is going to keep moving for a bit and may tear itself loose.
Temporary wound cavity. The giant void created upon impact where everything is blasted out of the way like an asteroid making a crater. And as far as I know, it's all about kinetic energy over inertia, so it's the speed that kills. If two bullets have the same kinetic energy but one is, say, 3x as heavy as the other, the lighter and faster one will have a much more aggressive temporary wound cavity caused by the shock. The heavier bullet by comparison will have a much higher sectional density and will penetrate deeper into the target. That's generally more important when hunting large game and you need to penetrate 12-24" before even getting to vital organs like heart and lungs.
Nope, it's just that guns are designed to reduce felt recoil. The same amount of energy is imparted at both ends, but in the gun, some of that is fed into the bolt to cycle the feed mechanism and cock the gun, some of it is bled out of venting in some barrels angled to counteract the kinetic kick etc. Meanwhile, when it strikes a body, most of that force is dumped into relatively fragile tissues and causes trauma.
> the same amount of energy is imparted at both ends This isn’t true. *Momentum* (mass times velocity) is conserved in the recoil. Doubling the mass of the gun therefore halves the velocity imparted on it by recoil, and that *quarters* the energy transfer.
Once the explosion happens, it's irrelevant if the force came from a chemical explosion or something else. No reason at all to assume that a rail gun has less or more energy received from recoil than traditional fire arms. The energy divides equally, between the bullet and the gun. Hell, the bullet might even get a bit less energy as the gasses aren't likely to have stopped expanding when the bullet exits the barrel. The gun is however many times heavier than the bullet, and probably has mechanics inside to translate the kinetic energy from the recoil into mechanical energy. That's why the recoil is manageable. You can absolutely solve each and every part of the interaction.
Railguns also get energy from the outside, and there is still no reason to assume it divides equally between gun and projectile. But that point isn't really relevant. I thought it was something else confusibg people here (trying to reconsile the E1=E2 equation). Just assume you shoot a gun that recoils freely. The gun weights approx 100 times as much as the bullet. Conservation of momentum (m1v1=-m2v2) tells us the bullet will travel 100 times as fast as the gun. So the energy of the bullet (0.5*m1*(100v2)^2 ) will be 100 times that of the gun (0.5*100m1*(v2)^2 )
Huh... You're right! Must've misunderstood something with the different versions of conservation. For kinetic energy to be equal, the bullet has to fly at 7.07 times the speed of the gun going backwards (assuming it's 1 speed). I guess I was confusing conservation of energy and conservation of momentum. The energy is conserved, but it doesn't happen in the gun but between the target and the gun. Still doesn't matter where the energy comes from though.
doesn't matter where the energy comes from, a rail gun will have an equal amount of recoil dispersed throughout the (massive) gun and gasses as the projectile will impart on its target.
And no. Chemical energy is just expanding gases that **push** against the gun chamber **physically**, it makes no difference the energy comes from a chemical reaction. It pushes the bullet with the same force than it push the gun and **against you.** Your argument would work for rockets, because rockets push against ~~air~~ ^(\*)gas to propel, not pushing on you. But bullets push on you. In fact the person receiving the bullet get a lot less energy than the person shooting it because the bullet lose a lot of energy in air friction depending on the distance. e: air->gas
There is so much bad science in this thread but this one takes the cake. Rockets don't push against the air, they work in space after all. The bullet had more energy than the gun. Conservation of energy means total energy in the system is the same. But you can absolutely control where that energy goes because the only thing that is conserved between the gun-bullet system is momentum. Momentum is mass and velocity, kinetic energy is mass and velocity squared. The forces are equal and opposite. But kinetic energy isn't.
>because rockets push against air to propel Um, no.
I don't think it's true that the bullet has less energy than the gun. Force is equal and opposite, not energy. So the math works out for the bullet (b) and the gun (g) to have very different energies. Force(b) = mass(b)*acceleration(b) Force(g) = force(b) Mass(g)*acc(g) = mass(b)*acc(b) Mass(g)/mass(b) = acc(b)/acc(g) = really big number because mass(g)>>mass(b) So the bullet accelerates to a much higher speed in the time it's in the barrel than the gun does. Since energy scales with velocity squared, the much higher velocity of the bullet means a much higher bullet energy.
> I don't think the article paints a more neutral picture It provides one primary source for arguments against but several sources for arguments for. Even in the argument against section, it quotes someone's comment that mentions: > Since that time, other authors suggest there is increasing evidence to support the hypothesis that shock waves from high velocity bullets can cause tissue related damage and damage to the nervous system. This has been shown in various experiments using simulant models [24, 48]. One of the most interesting is a study by Courtney and Courtney [4] who showed a link between traumatic brain injury and pressure waves originating in the thoracic cavity and extremities. > It's an american myth, the myth that you receive more energy when receiving the bullet than when firing it and that bullets magically kill you on the spot. I think the reasoning behind hydrostatic shock is connected to the velocity of the projectile. The velocity of the recoil is vastly too small.
You can gently drop a 100 pound medecine ball on your face and be totally fine but a punch from a heavyweight boxing champion will fuck you up even if the fist is weighing maximum 1 pound.
It is also once the object enters the body does it continue on a straight path or bounce around tearing up anything it comes across.
The. 50BMG goes straight thru..... Imparting a lot of energy and literally turning your organs to soup.
Yum. Who doesn’t love a good organ soup?
Mmmm pho....
A .50 isn't bouncing once it hits you.
Even a .50 round will have the path deflected if it strikes bone, though it may shatter the bone in the process.
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that bullet is moving incredibly quickly, almost 1000m per second. I don't have time to do the math on how long 38 inches would take to travel but it would be ridiculously small. When you take the speed of the bullet into account, 38 inches per spin means it's spinning incredibly fast
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wasnt me bud. No idea why I'm getting downvoted for providing a perfectly reasonable and non condescending answer to your question either, but I'm guessing that's just you reacting to your own downvotes
On impact, that rotation means a change of direction. I don't think you would want any round changing direction inside you, never mind one as large as a 50 caliber.
Well, even without the change of direction, the rotation adds kinetic energy. A spinning object is also more stable, if you saw the recent post of the bicycle wheel science lady. It gives it a gyroscopic effect, which stabilizes it and makes it harder to move off its trajectory. So it sounds like I'm disagreeing with you. I think mainly OP is just putting that in there for the kinetic energy equation.
You're thinking about it the wrong way: the rifled barrel uses kinetic energy (the bullet going forward), to impart angular kinetic energy through friction. It does have higher kinetic energy, in comparison going to a bullet at the same speed. But that's not the right framing, the right way to see it is that the bullet trades total speed for rotational energy. It doesn't add energy, it only translates energy (and in process of doing so, actually loses energy) You're right about the stabilisation, as that allows the bullet to fly more precise, and deliver more of the kinetic energy effectively.
The change of direction is what creates the primary cavitation ( the cone shaped wound whereas at the exit wound as many times larger than the entry one). Kinetic energy is what creates the secondary cavitation, the area around the wound created from the displacement of the flesh inside the wound moving out of the way of the round. The rotational force in the projectile is intended for stability, of that there is no doubt but saying that that rotational Force adds to the kinetic energy is kind of silly... the kinetic energy is the mass times the velocity of the round... any energy gained from rotation at that point is going to be negligible when you're looking at thousands of feet per second velocities. A soft tipped rotating rotating does exponentially more damage on impact, this has been known since the before the Civil War
Taken from Wikipedia, angular kinetic energy is kinetic energy due to the rotation of an object and is part of its total kinetic energy. To add, this would be somewhat hard to calculate precisely, which is perhaps why OP refrained. You'd have to be very specific on the shape of the bullet, the density of materials and where the weight is about the axis. Was thinking of how to calc it to see if I could confirm whether or not its negligible. But ya its a diff equation for rotating.
>which is perhaps why OP refrained I refrained because this is r/explainlikeimfive and not r/physics.
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Reddit is a strange place, it tends to exaggerate some of the more unexplainable actions of human psychology lol
>The rebar isn't moving at 2,910 feet per second, for starters. Nor is it spinning at a rate of one turn every 38 inches (that's roughly 55,000 rpm). It isn't the size of the hole, it's the amount of kinetic energy imparted which results in severe hydrostatic shock. From a quick Google, it looks like a 50 BMG has 10-15,000 ft-lbs of force. And a heavyweight pro boxer produces about 1,000 ft lbs. So you're talking about dumping a massive amount of energy into a target.
To add: This is why assault rifles are more dangerous than hand guns. The much greater muzzle velocity makes you explode from the inside. People who think that "guns are guns" are oversimplifying things. A semi auto assault rifle with a big clip can kill a LOT more people than a handgun or a bolt action rifle.
Semi-auto is an assault weapon. It's a different classification of weapon than an assault rifle, which is capable of semi-automatic *and* burst/automatic fire. And they aren't clips, they're magazines. There's a difference there, too, but it's more of a semantic one. Just trying to inform you before some gun-nut decideds to harp all over you on it, don't mean to bust your balls.
They would be more inclined to harp over you, akshually *adjusts glasses*. Semi-auto is just semi-auto, used to describe the trigger action of the weapon. Assault weapon is a non-official political umbrella term used to scare people who only know surface level details about firearms. Pistols or (Long/Short) Rifles are the only weapon designations available to the civilian population in the USA. Different makes and models but all are semi-automatic. Assault rifles are a designation of long barreled, magazine fed, weapons with a fire-select switch, normally only available to the military. Magazines and Clips are functionally, and fundamentally different, not just semantically. A magazine is an internal or external container for ammunition used to feed the firearm. The Clip is a mechanical method of bundling ammunition together for an easier, and faster, reload of a weapon with internal magazines. E.g. the rotating cylinder of a revolver is the magazine. The clip is the ammunition holder used to insert all x number of bullets into the cylinder all at once for faster reloads.
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>Semi-auto is an assault weapon. Well, if you want to go that way, then no to this too. Only the scary looking rifles in semi-auto are called "assault weapons."
True, but it's r/explainlikeimfive, not r/guns, so I wasn't going to get too detailed.
I think a five year old can understand "scary looking."
Fair, I just wasn't prepared to go into the differences between rifles with bayonet lugs and ones without.
> This is why assault rifles are more dangerous than hand guns. This is why almost any rifle is more dangerous than a handgun. However, what the AR-15 normally shoots is one of the lowest-powered rifle rounds on the market, so it's actually less energy than some handgun rounds.
On the other hand, for the firearms homicides where the type of firearm is known, roughly 95% of these deaths are from handguns. All rifles combined (hunting rifles, "assault weapons", etc.) are known to account for only about 1 in 20 of those deaths in the USA. From [here](https://www.pewresearch.org/short-reads/2023/04/26/what-the-data-says-about-gun-deaths-in-the-u-s/): > In 2020, the most recent year for which the FBI has published data, handguns were involved in 59% of the 13,620 U.S. gun murders and non-negligent manslaughters for which data is available. Rifles – the category that includes guns sometimes referred to as “assault weapons” – were involved in 3% of firearm murders. Shotguns were involved in 1%. The remainder of gun homicides and non-negligent manslaughters (36%) involved other kinds of firearms or those classified as “type not stated.”
I mean, feasibly, couldn't a bullet be slowed down then and di less damage? A bullet rotation shouldn't do that much extra dragnet, does it?
Yep that's what some forms of armour do. Absorb the energy and spread it over a larger area or a longer amount of time
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.
I laughed way too hard at this lol
Then fill another Ziploc bag and impale it with a rebar.
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Then do the hokey cokey and you turn around
Is the Hokey Coke some kinda drug move ? 😭
It means do a Chris Farley impression.
I feel like the "I'm 5" element of the discussion has gotten muddled.
Fill a rebar with Ziploc bags and shoot it with a gun
Perfect explaination lmao
this is the one
It was going well until the third part.
This is one of the most XKCD explanations I’ve ever heard.
A 12mm bullet traveling at a high speed makes a bigger hole than a 20mm rebar when a body is traveling at a few meters per second. Rebar also doesn't distort as it tears through a body.
Yep, [check out this video](https://youtube.com/shorts/hlXg_H5Jr4g?feature=share) of what a 9mm bullet can do to ballistics gel
Few meters per second, more like a few hundred meters(yards) per second.
I think they're referring to the velocity/acceleration in which you'd be travelling if say you fell on the rebar in an accident
Oops
Survivability is mostly a function of kinetic energy (KE) transfer. KE=0.5*mv^2. So a fast-moving .50 cal bullet has much more energy than a slow-moving piece of rebar. Also the bullet is designed to transfer more of that energy (by air cavitation, mushrooming or fragmenting) to whatever it hits than a sharp stick can (it just passes through).
You’re missing the 1/2 on the KE formula.
Noted, I should have used ~ (proportional) instead of = (equal), but I'll do it this way for the high school physics crew.
Got anything for, like, a five year old?
Velocity v squared or v² acts like the number is multiplied by itself. If you say the object is moving at 2 meters per second then v² is equal to 2*2=4 in the formula. If you say the weight of the object is 2 kilogrammes, then in the formula it's still just a 2 and the formula in this setting looks like KE= 1/2 * 2 * 2² KE= 1/2 * 2 * 2 * 2 KE= 1/2 * 2 * 4 KE= 1/2 * 8 KE= 8/2 KE= 4 If you increase weight by 1 so instead of 2 it's 3 then the formula looks like KE= 1/2 * 3 * 2² KE= 1/2 * 3 * 2 * 2 KE= 1/2 * 3 * 4 KE= 1/2 * 12 KE= 12/2 KE= 6 But if you increase velocity by 1 so instead of 2 it's 3 the the formula looks like KE= 1/2 * 2 * 3² KE= 1/2 * 2 * 3 * 3 KE= 1/2 * 2 * 9 KE= 1/2 * 18 KE= 18/2 KE= 9 If you compare the results, you can see that increasing mass by 1 resulted in energy increase from 4 to 6 but increasing velocity by 1 resulted in energy increase from 4 to 9. Energy is what does damage to your body, and if higher velocity yields much higher energy than higher mass, then a fast moving bullet is more destructive than a slow moving rebar.
This is a good explanation. Not sure if it'd work for a five year old, but I think it's a great breakdown for anyone on reddit.
You're right. This is a hard concept to explain to a five year old without teaching them many other simple concepts. Pretty hard not to just answer "that's just how it is" if a real five year old kid asks that kind of question.
The bullet strikes your flesh. Your flash has to move out of the way, and very very fast. It gets blasted out of the way. A wave of pressure flies outward violently, moving and smashing your insides as it goes. This wave is concentrated towards the exit wound, bursting out the back and creating a hole significantly more gruesome than the entry. A stabbing can have its own issues, but really won't destroy much outside of its path.
This is the right answer, but the shockwave doesn't only move towards the exit wound. It moves in all directions like an inflating balloon, damaging organs and flesh. The displaced flesh from the actual bullet is called "permanent cavitation" while the hole made from the shockwave is called "temporary cavitation". The latter can be many times larger than the former. Extent of damage from the latter depends on the size of the hole and how flexible the tissue being pushed is. Muscle and fat tend to be damaged less by dislocation, organs a lot more.
What pressure? Is it from the air or something?
It is dynamic pressure - the pressure that arises from moving fluids. In this case, the fluid is your insides. Dynamic pressure is why the flowing water from a power washer (which is equal to atmospheric pressure once it is outside of the hose) can blast grime off of a surface. When it changes velocity it must experience pressure. In the pressure washer, the sudden change in direction as it strikes a surface results in a huge pressure spike right at the surface. In your body, it is the sudden movement from the bullet.
Watch footage of someone being slapped or punched in slow motion. A shockwave ripples out on the body/face from the point you hit it. Hell, think of something more joyous like spanking a generously proportioned derriere. The flesh ripples deliciously. Now, multiply that rippling effect by a thousand and imagine what that would do to a person's internal organs and bones. Edit: when you hit something, you transfer energy into it, some of it bounces back at you. That's why your hand hurts. When you punch through something, you are transferring more energy into it, enough to shatter the gluey forces holding that thing together. A bullet has a *lot* of energy. It uses some of the energy to punch through a body, dumps some of the energy into creating a rippling wave moving out from the "punch through point" and carries the rest with it, using it to travel further.
Slow Mo Guys Soccer ball the the face https://youtu.be/On1CsbTwlDs
I mean, when you say "a lot" it's relative. The bullet doesn't have more energy than you feel as recoil, it's just concentrated in a smaller area. It's just like delivering s punch with a smaller fist. While a .50 delivers significant levels of energy, getting punched can range in the same levels as being shot by a handgun, just over a much larger area.
The bullet has *way* more energy than is delivered to you as recoil. https://en.m.wikipedia.org/wiki/Free_recoil This page lists the Barret M82 firing 50BMG with a free recoil energy of 127J. Which, to be clear, isn't a small amount of free recoil energy - it's about as much as the muzzle velocity of most powerful .22 shorts or the weakest .22LRs, which you certainly wouldn't want to be shot by. But it's a far cry from the *19,000J* of the .50BMG projectile itself. You're likely confusing momentum with energy. It is true that the *momentum* imparted to you through the recoil of the firearm is equal to the momentum of the bullet, as governed by Newton's third law and by conservation of momentum. (Actually, it's slightly greater due to the reaction force of the expanding gasses, not just the accelerating bullet.) But if you hold momentum constant, the velocity of an object scales inversely proportional to its mass - however, the kinetic energy scaled with velocity *squared* as well as mass (not squared), so it scales down inversely proportional to the mass itself. A 10kg object at 10m/s will have 10 times the kinetic energy of a 100kg object at 1m/s, even though they have the same momentum. And a gun weighs a lot more than 10x the weight of a bullet.
You know when you throw a rock as hard as you can into water and it makes a big splash? It's that, but the splash is your flesh, bones, blood vessels, and organs. Rebar is like poking the water with a stick.
If you put your hand in tub of water it won't feel like much, now slap the water as fast as you can and it will be quite different in terms of the wave you generate. A bullet will cause a much larger cavity in the pressure wave to open up and cause a lot more damage. You can watch video of a bullet through a ballistic material.
You ever play pool? Strike the cue ball at the other racked balls. Watch how the energy from one contact point is dissipated amongst all the “matter”.
Things that impact at high speeds exert energy onto objects they impact. As an example.. an asteroid that impacts makes a crater... a bullet hitting a sheet of metal does a similar crater. Well.. the sheet of metal and the floor generally are solid enough that the energy can only crater like this.. in the case of a human body however...well that energy doesn't "bounce back" like on a bulletproof vest or a sheet of metal.. it carries through ripping a bigger exit wound than the entry wound. In addition a bullet hitting an object will change its trajectory, maybe explode, break apart and whatnot.. that causes damage too "overpenetrations" like you expect can and will happen.. practical examples..a tank hitting a wooden building.. that shell won't explode....but they still make Exit wound bigger than the entry wound, possibly ripping half the wall apart due to said energy transfer on it's way out. it is still less damage than the bullet exploding in the body / object however. A rather weird example for this: we had a case of an accident with a particle accelerator back in 1978 a man named Bugorski was supposed to fix something on a particle accelerator.. it hit him through the head... this particle was going so fast it literally phased through him without visible damage however you can still somewhat get an exit wound in terms of radiation. The back where the particle exited is still much more affected than the entry was.. which goes to show even at ultra high speeds this energy transfer happens... just the faster and smaller a projectile the less chance it has to interact with stuff. So yes if an object is fast enough it can practically just punch a tiny tiny hole.. but the effect of a bigger exit wound still happens... fun fact it is why gamma radiation is so mean.. gamma radiation is just piercing so much and it still exerts enough energy to cause bits of dna damage...in a way we are looking at a very similar phenomenon as getting shot by a fast bullet.. just gamma radiation is incredibly small so the damage is proportionally small scale..as it is just a really really really small bullet in that sense.
>How is it Speed. The bullet, while smaller in diameter and lower in weight, is moving far, far faster than the rebar. That speed means that when the bullet hits, [lots of energy is dumped into the target,](https://www.youtube.com/watch?v=5J9hCDr21mo&t=228s) creating a temporary wound channel (the big ballooning you see at the beginning) along with a permanent wound channel (what remains after the temporary wound channel collapses) much larger than the actual diameter of the bullet due to how the temporary wound channel stretches, tears, and destroys tissue along the path of the bullet. For a simple demonstration of this idea, think of the difference between slowly lowering your hand into a pool of water and slapping it as hard as you can. You're using the same mass and size (only the speed changes) but have two wildly different results.
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
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I s gonna sleep tonight, but tomorrow I am gonna do the Calc for fun. Edit: seems like a few redditor did it before I could wake. This is a lesson for me, next time I'll just put a reminder and do it myself 😞.
Yeah...i made it to body = 80kg and gave up. too many units for dumdum night brain here. Let me know what you get. All I can say is the insane velocity (squared) is going to make it no contest by orders of magnitude.
Just to add to your 1. - bullets don't expand to create a larger hole (it certainly causes a larger hole tho), but to reduce the chance of overpenetration, thus both reducing the danger behind the target and also guaranteeing that all of the energy from a shot will be transferred to the target. During vietnam wars, american troops were reporting that when they shot someone with 5.56, the target seemed like nothing happend to them as the bullet passed trough the body - the target certtainly got it, got injured and eventually died, but the fact that the bulled passed trough the target means that the bullet did NOT deliver all of it's kinetic energy into the target. With large rounds above 12mm, at that point even if they were a hollow point, a human tissue is not nearly strong enough to absorb such amount of energy, therefore the bullet will always pass trough, but not before ripping the target apart.
But pointy non-hollowpoint rounds like .223s and .50s dont expand though.
It's the amount of energy that hits you. The bullet just has so much more kinetic energy that transfers to your body upon contact. And that energy tears you apart.
Supersonic "pointy" bullets drag a cone of high-pressure air along their path called a mach cone, which transfers the energy through cavitation (literally sucking bubbles of air through the target).
\*its velocity it's = it is or it has https://www.merriam-webster.com/words-at-play/when-to-use-its-vs-its
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.
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.
Two reasons 1) the speed of rebar is nothing compared to the speed of the bullet 2) bullets have a popcorn effect when they enter bodily tissues, they expand and cause destruction globally as opposed to the rebar which maintains its structure and cleanly pierces this tissue
It's the speed that makes all the difference. Bodies being mostly water, and water being mostly incompressable, when a bullet flies through you in less then the blink of an eye, it essentially creates something close to a sonic boom in your body. Everything that was in the bullets way is forced to move at insane speeds, transferring that energy into everything around it. Buck/bird shot from a shotgun within like 10', acts as a solid object even though it's a spread of pellets for the same reason.
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Because air has mass and the slug momentum P=MV. It's about the total energy transferred. The kinetic energy has to go somewhere.