Energy Dump - A Self-Defining Term

[Vern Humphrey]

Yes, it may, it may not.

There are many more factors, including that of individual reponse. I am only addressing the concepts of energy transfer/dump/damage in that post. It seems to be common knowledge that different people may react differently to seemingly identical wounds.

Precisely correct -- which is why the "energy dump" theory is so tenuous.

When a moving object imparts motion to a stationary object, that is an example of momentum. A fist, club, or automobile causes the impacted thing to move -- and a bullet doesn't. Indeed if a typical bullet could literally "knock a person down," all of it's energy would be expended as momentum and the damage to the person would be minimal.

Now there are legitimate reasons to fear over-penetration in ammunition intended for self-defense or law enforcement, including the possibility that innocent bystanders may be killed or injured. But from the standpoint of stopping or killing, there is no advantage to a bullet not penetrating through-and-through.

 

[fletcher]

Energy and momentum are not convertible in the manner you're suggesting. Kinetic energy will only convert to kinetic energy, and momentum only to momentum. While the transfer of kinetic energy to an otherwise immobile object will result in the creation of some momentum, it's not all interchangeable. It's the laws of both conservation of momentum and conservation of energy.

there is no advantage to a bullet not penetrating through-and-through.

For personal defense rounds, we have no choice as to whether or not the bullet will go through, and still keep all other factors the same. We can only choose the type of round. Having looked at the wound channels of FMJ versus JHP, I'll take the much larger permanent cavity created by a good JHP.

 

[Vern Humphrey]

Energy and momentum are not convertible in the manner you're suggesting.

Bingo!

That's why examples using momentum are not applicable to discussions of kinetic energy.

And that's why I said:

Indeed if a typical bullet could literally "knock a person down," all of it's energy would be expended as momentum and the damage to the person would be minimal.

 

[fletcher]

That's why examples using momentum are not applicable to discussions of kinetic energy.

They're tied together, not exclusively separate. The examples of stick/car/etc. don't hold.

Indeed if a typical bullet could literally "knock a person down," all of it's energy would be expended as momentum and the damage to the person would be minimal.

Even though bullets cannot knock people down, they can sure cause a good bit of trauma, such as behind a bulletproof vest. Adding more speed until it could knock someone down (assuming the vest will still stop it), could very well kill someone AND knock them down. Sudden impact will not come without massive energy transfer.

 

[Vern Humphrey]

They're tied together, not exclusively separate. The examples of stick/car/etc. don't hold.

That's true.

Quote:
Indeed if a typical bullet could literally "knock a person down," all of it's energy would be expended as momentum and the damage to the person would be minimal.

Even though bullets cannot knock people down, they can sure cause a good bit of trauma, such as behind a bulletproof vest. Adding more speed until it could knock someone down (assuming the vest will still stop it), could very well kill someone AND knock them down. Sudden impact will not come without massive energy transfer.

It's difficult to imagine a bullet that could knock someone down and not penetrate a vest. But should that happen, the result would be from momentum, not kinetic energy.

 

[fletcher]

But should that happen, the result would be from momentum, not kinetic energy.

Yes, the bulk movement alone would be a result of momentum. But, things such as the car, stick, fist, do not injure tissue because of momentum. They injure and damage from energy transfer.

It's very important to know that momentum accounts for bulk movement with no deformation. On the scale we're looking at, which specifically involves damage to tissue (HEAVY deformation), energy is the only factor worth considering.

 

[Kentak]

Let's use the example of bow hunting. Arrows might weigh about 500 grains and travel at 250 fps. Low momentum and low energy. However, pretty good penetration, often going right through the animal. Yet, stopping power is minimal. Unless there is a fortuitous heart or CNS hit, the animal will run away to drop later from internal or external bleeding.

Good penetration does not always equal good stopping ability.

K

 

[FerFAL]

Yup, that's a good example Kentak

FerFAL

 

[Vern Humphrey]

Let's use the example of bow hunting. Arrows might weigh about 500 grains and travel at 250 fps. Low momentum and low energy. However, pretty good penetration, often going right through the animal. Yet, stopping power is minimal. Unless there is a fortuitous heart or CNS hit, the animal will run away to drop later from internal or external bleeding.

Good penetration does not always equal good stopping ability.

And arrows are not bullets.

However, the most common "stopping factor" is bleed-out. Absent a CNS hit, a deer will often run until it bleeds out. Under the same circumstances, a determined attacker will continue his attack until his blood pressure drops to the point he is unable to continue.

 

[Soybomb]

Shoot a bottle of water with a 9mm 115 FMJ round and see what happens ( nothing)
Shoot another bottle with a 9mm round loaded with a light piece of brass rod, traveling at 2000 fps, and that bottle with explode when hit.
Both will penetrate plenty, but the one traveling at 2000 fps will have much greater hydraulic shock, affecting organs in a similar way as it does with a bottle of water. Penetration alone is not enough.

Today's experts int he field say that the concept of "hydraulic shock" being a reliable stopping mechanism is bunk with handgun round. I recommend you read the fbi handgun wounding document linked several times in this thread. If you still disagree I'd like to know what you base your disagreement on. On one hand I have several doctors telling me that the actual physical hole I punch with a handgun is all I can rely on, on the other I have a couple guys on the internet telling me they're wrong but not citing supporting evidence.

 

[Odd Job]

@ Vern Humphrey

The following radiographs are from my old gunshot library (cases from the late 90s when I was in Johannesburg). I saw all three patients in the flesh and X-rayed the first two myself. One of my colleagues X-rayed the last one (bandaged and on a makeshift splint).



These are three gunshot wounds, all involving the distal forearm. These were three unrelated cases where adult males were shot and brought to hospital.

Case A was a single handgun wound (of unknown calibre) that perforated the distal forearm and caused a comminuted fracture of the radius. Note the minimal displacement of the bone fragments. No metallic projectile fragments were seen in the wound. The geometry of the fracture suggests (but does not confirm) that this was a service calibre round. The radial artery was undamaged.

Case B was a single 12 gauge shotgun blast to the forearm. The cartridge was an SSG (not sure what that is in American money) but I can weigh one of those pellets if you absolutely have to know. This was a perforating wound also, but some pellets were penetrating only. This man was shot by police. Note the multiple fractures and deformed pellets in the wound. Note that despite the multiple fractures, there is not that much displacement of the bone fragments. I don't have records of any vascular injuries in this case, but I know that the arm was repaired and the patient recovered.

Case C was a single perforating wound caused by a 5.56mm projectile fired from a Galil clone (a South African R5 rifle). This was also a suspect shot by police. Note that the bones of the radius and ulna are fractured and markedly displaced in a radial dispersion pattern. There is also deposition of multiple fine lead specks in the wound, but no jacketing. This effect can be seen when lead is squeezed out of the base of a rifle round or when a rifle round fragments when traversing tissues. We call this effect the 'lead snowstorm.'
The key thing here is that the bones were not displaced by the passage of the bullet directly (which is what happened in Case A and B). They were displaced by the temporary cavity. The small lead specks do not have enough mass to fracture the bones in that manner and indeed their distribution cannot be directly associated with any of the fractures (unlike Case B).

You may be interested to know that the radial and ulnar arteries were extensively damaged and not enough of the soft tissues were viable in this case. The man had to have an amputation.

Now, sir, I challenge you to explain to me how the marked displacement of bones and extensive soft tissue damage in Case C took place without the effects of cavitation due to the high velocity of the round.

 

[Vern Humphrey]

Yes -- different wounds do look different. But that's not the "energy dump" theory. For one thing, the "energy dump" theory postulates that a bullet which does not exit the body does more damage than one which does exit -- all other things being equal.

No one denies that a bullet which fragments or expands will produce a different effect from one which does not. No one denies that a bullet that hits bone and drives fragments of bone and bullet material off the original trajectory will damage more tissue.

But that's not the "energy dump" theory.

 

[Kentak]

Vern,

You said

A .45 at 1,000 fps is a formidable round, and will kill just as well as a .243 with more energy, all other things being equal. "Energy dump" is a myth.

I'm surprised no one else has responded to this.

I'm not a hunter. Perhaps those that are could weigh in on this.

While I agree a .45 at 1000 fps is a formidable round, I simply do not believe that it will "...kill just as well... as a .243 traveling at almost 3000 fps and having more than 4 times the kinetic energy. While we can, and are, debating the *effectiveness* of "energy dump," I don't think you can dismiss it as a myth--and certainly not in the case of the two rounds you are comparing in this example.

Are you saying a .45 will drop a 300 lb mule deer buck as effectively as a .243?

Would anyone else reading this thread choose the .45 over the .243 if you had one shot at a determined attacker? Or, I should say, would any one NOT jump and choose the .243?

K

 

[JesseL]

Now, sir, I challenge you to explain to me how the marked displacement of bones and extensive soft tissue damage in Case C took place without the effects of cavitation due to the high velocity of the round.

Take a piece of dry spaghetti and hold it by the ends. Bend it until it breaks. Examine how many pieces your noodle has broken into and which directions they went. Explain how much cavitation was applied to the dry pasta.

When the 5.56mm bullet struck the bone it imparted enough momentum to that portion of the bone that it exceeded the structural limits of the bone as a whole. You've just got a bone that's being pushed in several directions at once and it's not strong enough to resist those forces.

 

[Odd Job]

@ Vern

Kentak asked you:

Let's say a 30 cal steel ball traveling at 1500 fps has just enough mustard to traverse through a certain human target. You're not saying that the same steel ball traveling at 3000 fps and taking the same path through the body wouldn't be more destructive or have more stopping ability, are you?

And you replied in the affirmative. My observations with the cases above prove that this is not the case. The high velocity round causes more damage by virtue of cavitation. The cases I provided are all perforating gunshot wounds. This is not about energy dump, it is about cavitation.

@ JesseL

Take a piece of dry spaghetti and hold it by the ends. Bend it until it breaks. Examine how many pieces your noodle has broken into and which directions they went. Explain how much cavitation was applied to the dry pasta.

The spaghetti analogy is not applicable because the forces that were applied to the bones were not opposing, they were radial. Furthermore the bone is not homogeneous and is not comparable to spaghetti. You are also ignoring the documented soft tissue damage in Case C.

When the 5.56mm bullet struck the bone it imparted enough momentum to that portion of the bone that it exceeded the structural limits of the bone as a whole. You've just got a bone that's being pushed in several directions at once and it's not strong enough to resist those forces.

No, sir. If the bones were being pushed in several directions at once, then no discernible radial displacement would be seen radiologically. Furthermore, if it was simply a question of bone being displaced by direct contact with the projectile, then the soft tissues would still be viable and the ulnar and radial arteries might have escaped damage. Certainly he would not have lost his hand.

 

[Kentak]

But that's not the "energy dump" theory.

Whoa. who said a high energy round *has* to remain in the body for the benefits of high energy to be available?

Round A passes through the body.

Round B passes through the body.

All other things being equal, if round B had more kinetic energy than round A going in, it sure as heck won't cause *less* damage, and sure as heck could cause a lot more depending on how much more energy it had.

If I'm wrong, I need someone to explain why.

K

 

[Vern Humphrey]

While I agree a .45 at 1000 fps is a formidable round, I simply do not believe that it will "...kill just as well... as a .243 traveling at almost 3000 fps and having more than 4 times the kinetic energy. While we can, and are, debating the *effectiveness* of "energy dump," I don't think you can dismiss it as a myth--and certainly not in the case of the two rounds you are comparing in this example.

There is "dead" and then there is . . . "dead."

There is no such thing as "deader." A 255 grain flat nose at 1000 fps will make your mule deer dead, as dead as any other round.

Are you saying a .45 will drop a 300 lb mule deer buck as effectively as a .243?

Probably better -- the .243 is considered by many to be marginal for mule deer. The primary advantage the .243 has is in it's extended range.

 

[Vern Humphrey]

And you replied in the affirmative. My observations with the cases above prove that this is not the case. The high velocity round causes more damage by virtue of cavitation. The cases I provided are all perforating gunshot wounds. This is not about energy dump, it is about cavitation.

So we have an alternate theory here, the theory of cavitation?

 

[Vern Humphrey]

Whoa. who said a high energy round *has* to remain in the body for the benefits of high energy to be available?

The proponents of "energy dump" theory said that. They postulate that a bullet which does not exit "dumps all its energy" in the body and is therfore more effective.

Round A passes through the body.

Round B passes through the body.

All other things being equal, if round B had more kinetic energy than round A going in, it sure as heck won't cause *less* damage, and sure as heck could cause a lot more depending on how much more energy it had.

If I'm wrong, I need someone to explain why.

Actually, as you have phrased it, the burden of proof is on you. You are the one making the affirmative claim.

I am saying the hole kills. The deeper and wider the hole, the more effective the round will be, all other things being equal. And the deepest possible hole is a through-and-through hole.

This explains why cartridges like the .45 Colt, .45-70 and so on are such effective killers all out of proportion to their kinetic energy levels. It also explains why expanding bullets are more effective than FMJs in smaller calibers -- they get bigger on impact and make bigger holes.

 

[easyg]

Yes, the bulk movement alone would be a result of momentum. But, things such as the car, stick, fist, do not injure tissue because of momentum. They injure and damage from energy transfer.

Exactly!

The momentum of the punch does not do the damage, what does the damage is the amount of energy the punch "dumps" into the target.

Consider this:
You punch your opponent as hard as you can and you hit him right in the middle of his torso.
It hurts him because you dumped all of the energy into your opponent's body.

But if you duplicate the first swing (same force and same momentum) but only connect with a glancing blow to the torso, and you punch continues beyond your target, it does not harm your opponent near as much because you did not "dump" all of the energy into his body.

 

[fletcher]

When the 5.56mm bullet struck the bone it imparted enough momentum to that portion of the bone that it exceeded the structural limits of the bone as a whole.

It transferred energy, not momentum, to fracture the bone. Momentum transfer alone does not cause damage.

All other things being equal, if round B had more kinetic energy than round A going in, it sure as heck won't cause *less* damage, and sure as heck could cause a lot more depending on how much more energy it had.

It certainly *could* cause more, seeing as there is more energy available.

 

[FerFAL]

Soybomb wrote:
On one hand I have several doctors telling me that the actual physical hole I punch with a handgun is all I can rely on

Well Soybomb, gotta ask, how many people did those doctors shoot?

If you still disagree I'd like to know what you base your disagreement on.

My opinions are based on the conclusions I arrive after considering what I learn from real life shootings.
I talk often with guys that kill people and got shot at. Unfortunately this happens all day long here in the suburbs of Buenos Aires. I try to listen to what guys that have been in gunfights have to say, both civilians and police.
That’s how I know that 124 FMJ 9mm is not much of a stopper but will put people down if you do your part ( shoot accurately, repeat if needed) and 45 ACP 230 gr FMJ works MUCH better.
Believe whatever you want.

FerFAL

 

[Vern Humphrey]

The momentum of the punch does not do the damage, what does the damage is the amount of energy the punch "dumps" into the target.

You can easily show that a good punch has as much kinetic energy as a .45 bullet. So how come it doesn't kill like a .45 bullet?

Because it's expressed as momentum, not KE.

 

[easyg]

Quote:
Are you saying a .45 will drop a 300 lb mule deer buck as effectively as a .243?

Probably better -- the .243 is considered by many to be marginal for mule deer. The primary advantage the .243 has is in it's extended range.

Not a chance.
If the .243 is considered "marginal" for mule deer, then the .45 is considered sub-marginal at best.
Have you ever noticed that the vast majority of handgun hunting rounds have high velocities and very high amounts of energy.

I am saying the hole kills. The deeper and wider the hole, the more effective the round will be, all other things being equal.
And the deepest possible hole is a through-and-through hole.

A hole alone does not kill, neither does energy alone, or penetration alone.
It is a combination of all three.
The ideal defensive round would have adequate penetration to hit vital organs, have a large enough slug to cause a respectable size hole, and have as much energy to dump as possible from a handheld weapon....and still be controllable when shooting.

But penetration totally through the human body does always give better results when it comes to firearms.
It's no great secret that hollow-point are typically more effective at stopping folks than ball ammo...and hollow-points typically don't over-penetrate the body as much as ball ammo.

 

[fletcher]

You can easily show that a good punch has as much kinetic energy as a .45 bullet. So how come it doesn't kill like a .45 bullet?

Because it's expressed as momentum, not KE.

Absolutely incorrect if you're looking at physical damage. Energy does work, such as damaging tissue, not momentum. Momentum models movement, not deformation. This is true for ALL cases.

Also, a punch doesn't tear through you for a number of reasons - comparing the two is apples and oranges. A more accurate comparison would be taking a .45 through a bulletproof vest for the blunt force.