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Old September 25, 2012, 12:57 AM   #51
Frank Ettin
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Quote:
Originally Posted by SRH78
...I can tell you this, a 45 Colt and 454 Casull shoot the same diameter bullet and neither shoots 2500 fps but the difference on game is like night and day. With the Colt, I can shoot cottontails and eat right up to the bullet hole. With the Casull, there isn't much left of a jackrabbit...
Again, your comparisons aren't useful. There's a big difference in body mass between a rabbit (cottontail or jack) and a human.

Quote:
Originally Posted by SRH78
...A 45-70 at 1700-1800 fps with a soft nosed bullet will leave a huge exit wound on a hog...
And that's a matter of the combination of high sectional density of the bullet, a heavy bullet and good bullet construction producing meaningful expansion at the relevant velocities.

But let's see what some people with professional credentials who have scientifically studied the subject say:
  • For example Dr. V. J. M. DiMaio (DiMaio, V. J. M., M. D., Gunshot Wounds, Elsevier Science Publishing Company, 1987, pg. 42, as quoted in In Defense of Self and Others..., Patrick, Urey W. and Hall, John C., Carolina Academic Press, 2010, pg. 83):
    Quote:
    In the case of low velocity missles, e. g., pistol bullets, the bullet produces a direct path of destruction with very little lateral extension within the surrounding tissue. Only a small temporary cavity is produced. To cause significant injuries to a structure, a pistol bullet must strike that structure directly. The amount of kinetic energy lost in the tissue by a pistol bullet is insufficient to cause the remote injuries produced by a high-velocity rifle bullet.
  • And further in In Defense of Self and Others... (pp. 83-84, emphasis in original):
    Quote:
    The tissue disruption caused by a handgun bullet is limited to two mechanisms. The first or crush mechanism is the hole that the bullet makes passing through the tissue. The second or stretch mechanism is the temporary wound cavity formed by the tissue being driven outward in a radial direction away from the path of the bullet. Of the two, the crush mechanism is the only handgun wounding mechanism that damages tissue. To cause significant injuries to a structure within the body using a handgun, the bullet must penetrate the structure.
  • And further in In Defense of Self and Others... (pp. 95-96, emphasis in original):
    Quote:
    Kinetic energy does not wound. Temporary cavity does not wound. The much-discussed "shock" of bullet impact is a fable....The critical element in wounding effectiveness is penetration. The bullet must pass through the large blood-bearing organs and be of sufficient diameter to promote rapid bleeding....Given durable and reliable penetration, the only way to increase bullet effectiveness is to increase the severity of the wound by increasing the size of the hole made by the bullet....
  • Urey Patrick was in the FBI for some 24 years, 12 of which were in the firearms training unit where he rose to the position of Assistant Unit Chief. John Hall is an attorney who spent 32 years in the FBI, including serving as a firearms instructor and a SWAT team member.
And in case you or anyone else is interested, I've attached a copy of an FBI paper entitled "Handgun Wounding Factors and Effectiveness."
Attached Files
File Type: pdf fbi-hwfe-1.pdf (203.5 KB, 33 views)
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Last edited by Frank Ettin; September 25, 2012 at 10:09 AM. Reason: correct typo
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Old September 25, 2012, 01:51 AM   #52
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Folks may want to drop by here and poke around some...

http://www.brassfetcher.com/index_files/9mmvs45ACP.htm

http://www.brassfetcher.com/index_files/357Magnum.htm

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Old September 25, 2012, 07:22 AM   #53
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Quote:
In a defensive rd for a handgun which is more important to consider....muzzle velocity or muzzle energy?
After mulling this over for a few days,,,,,I came to the conclusion that muzzle energy is either there or it isn't - there's not a lot I can do about that figure.

I go with muzzle velocity as being the more important of the two.

When I handload a round, I always have a specific velocity figure in mind that I want to hit.
I don't recall ever starting out to work up a load based on muzzle energy.

OTOH though,,,,the OP specified defensive rd. - not handloads or hunting loads.
There again though,,,I always look at the velocity of a particular round before I look at the muzzle energy.
The second thing I look at is the bullet weight.
I expect a high velocty to translate into a higher energy figure - which is why I say, it's either there or it isn't.
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Old September 25, 2012, 09:26 AM   #54
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Quote:
Originally Posted by Frank Ettin:
Again, you're comparisons aren't useful. There's a big difference in body mass between a rabbit (cottontail or jack) and a human.
Nice citations, Frank.

It's about the relative magnitude of the cavities - temporary and permanent- as compared to the size of the critter (or bad guy) bein' effected by those temporary and permanent cavities.
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Old September 25, 2012, 12:28 PM   #55
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Energy is more important.

Whether you like a slow and heavy round, or a light and fast round, you still want a high energy round.

Low energy rounds just suck, like a 35g .25 auto from a 2" barrel, which will only give you around 60 ft. lbs. of energy.

Or a 60g .32 auto from a 4" barrel, which only give you around 120 ft. lbs. of energy.




Compare that to a 200g .45+P from a 5" barrel, which will give you over 500 ft. lbs. of energy.

Or a 125g .357 magnum from a 4" barrel, which will give you around 580 ft. lbs. of energy.

Or a 155g .40S&W from a 4" barrel, which will give you around 500 ft. lbs. of energy.

High energy rounds are just more effective than low energy rounds (when it comes to quickly stopping aggressive humans) regardless of the velocity, IF the bullet stays inside the target and dumps all of its energy in to that target.
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Old September 25, 2012, 12:42 PM   #56
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For those who poo-pooed the autopsys of animals, they do represent living tissue, which ballistic gelatin, pine boards, Duxseal and other media do not.

The bullet's relative performance on living animals, large or small, is a good representation of the bullet's effect on human beings. Remember in testing the .45 ACP the Army used live goats for tests.

But a bullet that does not expand on a small critter, won't expand in the human body. And a bullet that expands too soon in an animal, will likely expand too soon on the human torso.

Common sense must dictate any observation.

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Old September 25, 2012, 12:46 PM   #57
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Hal wrote:

Quote:
,,the OP specified defensive rd. - not handloads or hunting loads.
Is there any reason defensive rounds can't be both?

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Old September 25, 2012, 12:49 PM   #58
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Depends on the animal, Bob.

For large quadrupeds, loads are normally designed with more penetration potential than is considered optimal for human targets. This raises concerns about over-penetration and inadequate expansion.
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Old September 25, 2012, 01:09 PM   #59
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I will say this, from my observations, I elect to use the .44 caliber Remington Semi-Jacketed Hollow Point bullet as my personal defense selection.

I have observed its effect on animate tissue loaded in the .44 Magnum. So, I elect to use it in my .44 Special. Until I'm proved wrong in actual practice, this will be my choice for daily carry.

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Old September 25, 2012, 01:25 PM   #60
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Quote:
Originally Posted by peacefulgary
...Low energy rounds just suck, like a 35g .25 auto from a 2" barrel, which will only give you around 60 ft. lbs. of energy.

Or a 60g .32 auto from a 4" barrel, which only give you around 120 ft. lbs. of energy....
Actually, the reason these cartridges will tend to perform poorly is not a matter of energy as energy. Rather, these are small caliber bullets making small holes, and with low sectional density and low momentum making for poor penetration.

Quote:
Originally Posted by peacefulgary
...High energy rounds are just more effective than low energy rounds (when it comes to quickly stopping aggressive humans) regardless of the velocity, IF the bullet stays inside the target and dumps all of its energy in to that target...
[1] You can't separate energy from velocity because energy is a function of the square of the velocity.

[2] But "energy dump" is meaningless.

[3] See post 51 for the back-up for my opinion.

[4] The effectiveness of a cartridge for self defense is related to the amount of tissue damage and resultant blood loss. And that is related to the diameter of the hole (permanent wound cavity) made by the bullet as long as it penetrates sufficiently.

Quote:
Originally Posted by Bob Wright
...The bullet's relative performance on living animals, large or small, is a good representation of the bullet's effect on human beings...
Yes and no. As the animal begins to approach the size of a human, a necropsy (postmortem examination of a non-human subject) will probably provide a fair amount of useful information about the bullet's effect on tissue, but not necessarily its effectiveness for self defense.

The physiological effects of any particular amount of tissue damage would be vastly different for a 200 pound man compared with a 20 pound mammal. The man has greater depth, density and amount of musculature, heavier bones, larger organs and a much greater blood volume. If, for example, a bullet damages 0.5% (by weight) of a 20 pound animal's total tissue mass (about 1.6 ounces), that amount of tissue damage is only 0.05% of the 200 pound man's total tissue mass. And even 2% of the dog's tissue mass is still only 0.2% of the man's.

Understand that there are four ways in which shooting someone stops him:
  1. psychological -- "I'm shot, it hurts, I don't want to get shot any more."
  2. massive blood loss depriving the muscles and brain of oxygen and thus significantly impairing their ability to function
  3. breaking major skeletal support structures
  4. damaging the central nervous system.

Depending on someone just giving up because he's been shot is iffy. Probably most fights are stopped that way, but some aren't; and there are no guarantees.

Breaking major skeletal structures can quickly impair mobility. But if the assailant has a gun, he can still shoot. And it will take a reasonably powerful round to reliably penetrate and break a large bone, like the pelvis.

Hits to the central nervous system are sure and quick, but the CNS presents a small and uncertain target. And sometimes significant penetration will be needed to reach it.

The most common and sure physiological way in which shooting someone stops him is blood loss -- depriving the brain and muscles of oxygen and nutrients, thus impairing the ability of the brain and muscles to function. Blood loss is facilitated by (1) large holes causing tissue damage; (2) getting the holes in the right places to damage major blood vessels or blood bearing organs; and (3) adequate penetration to get those holes into the blood vessels and organs which are fairly deep in the body. The problem is that blood loss takes time. People have continued to fight effectively when gravely, even mortally, wounded. So things that can speed up blood loss, more holes, bigger holes, better placed holes, etc., help.

So as a rule of thumb --
  • More holes are better than fewer holes.
  • Larger holes are better than smaller holes.
  • Holes in the right places are better than holes in the wrong places.
  • Holes that are deep enough are better than holes that aren't.
  • There are no magic bullets.
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Old September 25, 2012, 02:39 PM   #61
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Quote:
Again, your comparisons aren't useful. There's a big difference in body mass between a rabbit (cottontail or jack) and a human.
There is not a big difference between the body mass of a deer or hog and a human, though, and there is still a significant difference in the amount of damage done.


As for credentials, they are great but simply saying "pistol bullets" is like saying a Vespa, a Fatboy, and a Hayabusa are bikes or that an S10 and a Peterbuilt are trucks. They are very different things and a 147 grain 9mm fmj and a 125 grain 357 magnum hp from a 6" barrel are different things.

Also, different types of tissue react very differently. I have shot hogs with a 30-06 whose lungs were turned to mush but the heart was unharmed. I once shot a rat with a 300 grain xtp mag. It literally exploded and it's heart stuck to a buddy's jeans and was in one piece. There is also what happens when bullets strike bone and the bone fragments cause additional damage. There are lots of variables.

One thing doesn't change though. Work cannot be done without energy, period. Therefore, damage must come from the combination of having enough energy and using that energy effectively. That is a very simple fact. What you are trying to debate and where the real debate lies is just how effectively that energy is used. I have said from the beginning that is a major variable and that larger bullets are generally more efficient at doing so.
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Old September 25, 2012, 03:10 PM   #62
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Quote:
Originally Posted by SRH78
...Work cannot be done without energy, period. Therefore, damage must come from the combination of having enough energy and using that energy effectively. That is a very simple fact. What you are trying to debate and where the real debate lies is just how effectively that energy is used...
The error is to focus on energy. A suitably effective cartridge will have adequate energy. But it is not the energy that is causing the cartridge to be effective; it is not the energy causing the damage (at least at the range of velocities of handgun cartridges customarily used for self defense). It is the combination of factors resulting in a bullet of large enough diameter penetrating deeply enough; the necessary tissue damage is caused by the penetration of the bullet.

Of course, for the bullet to be effective in that way, it must have sufficient mass and momentum. And if it has sufficient momentum, it will have some certain minimum energy as well, since momentum and energy each vary with velocity.

But while momentum is proportional to velocity, energy is proportional to the square of the velocity. Therefore it is possible for a perhaps more effective cartridge, with a larger diameter bullet designed to expand appropriately at the velocity at which it is driven and having a large mass and high sectional density, to have less energy than a cartridge firing a small diameter, light bullet with a considerably lower sectional density but at a higher velocity and thus a higher energy.
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Old September 25, 2012, 05:07 PM   #63
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Quote:
,,the OP specified defensive rd. - not handloads or hunting loads.

Is there any reason defensive rounds can't be both?
A lot of people - myself included - don't think it's wise to use handloads for SD.
Hunting loads may be a bit on the hot side for indoor use.
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Old September 25, 2012, 05:21 PM   #64
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I am actually not focused on energy. I am simply making a point. What concerns me is the amount of it that can be used effectively and that has an awful lot to do with bullet construction, yet another variable, and what we consider effective for a given task.

I am going to make up numbers here just to illustrate my point.

Lets say we have 2 cartridges. 1 has 500 ftlbs and uses 400 of those effectively to create damage. 2 has 800 ftlbs and uses 500 of those effectively to create damage. Assuming that damage is done to equivalent areas of the target, cartridges 2 is less efficient but more effective.

On the other hand, if cartridge 3 has 600 ftlbs and uses 300 of those effectively, it will be less effective than cartridge 1.

Again, I am not talking about energy being dumped into the target. I am talking about energy being effectively used to create damage. In all cases, energy is a limiting factor. You can't do X amount of damage without at least X amount of energy to work with.

The application is much more complex with many variables but the basic concept is simple.

Energy = potential
energy used effectively = damage
bigger bullets = usually use more of their energy effectively


Obviously, none of this takes into account many other highly important variables like accuracy, rate of fire, ability to recognize the threat, ability to draw and get on target quickly, the nerve to do what is necessary, accounting for innocents who could be in here's way... The original question was velocity vs energy and the obvious answer is energy. They actually can be separated for the sake of argument, particularly when comparing multiple calibers. Given the same bullet however, no they couldn't.

An example would be comparing the 5.7x28 to a 40. The 5.7 has a lot more velocity but less energy. Right or wrong, that is how I interpreted the original question.
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Old September 25, 2012, 05:59 PM   #65
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Quote:
As for credentials, they are great but simply saying "pistol bullets" is like saying a Vespa, a Fatboy, and a Hayabusa are bikes or that an S10 and a Peterbuilt are trucks. They are very different things and a 147 grain 9mm fmj and a 125 grain 357 magnum hp from a 6" barrel are different things.
Absolutely!
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Old September 25, 2012, 06:02 PM   #66
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Quote:
Originally Posted by SRH78
...An example would be comparing the 5.7x28 to a 40. The 5.7 has a lot more velocity but less energy. Right or wrong,...
Right, but not by much. The .40 S&W has only a very little more energy, and in some loadings, it has less.
  • According to this source, 5.7x28 --

    1. 32 gr FMJ -- 397 ft-lb

    2. 40 gr JHP -- 340 ft-lb

  • According to published specifications for Federal Ammunition, .40 S&W --

    1. 165 gr Hydra-Shok -- 352 ft-lb

    2. 180 gr Hydra-Shok -- 400 ft-lb
Quote:
Originally Posted by SRH78
...I am going to make up numbers here just to illustrate my point.

Lets say we have 2 cartridges. 1 has 500 ftlbs and uses 400 of those effectively to create damage. 2 has 800 ftlbs and uses 500 of those effectively to create damage. Assuming that damage is done to equivalent areas of the target, cartridges 2 is less efficient but more effective.
...
But since it this is made up, it really doesn't mean anything. And how do you come up with this sort of notion? Do you have any evidence to support this conjecture? Can you cite any authority to support it. As the experts I quoted in post 52 point out, the energy doesn't create the damage.

Your fundamental premise is fallacious.
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Old September 25, 2012, 06:03 PM   #67
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From the perspective of evaluating/determining which factor is most important in terminal ballistics, I think that Duncan MacPherson, one of my favorite authors on the topic, nails it pretty well here-

Excerpt from "Bullet Penetration"
Quote:
“. . . every now and then someone wants to analyze or think about a problem involving energy, and when they attempt to do this without really understanding energy or other thermodynamic concepts the result is unfortunate. One such problem is the analysis of any of the various aspects of terminal ballistics; some individuals with inadequate technical training and experience have unwisely and unproductively attempted to use energy concepts in the analysis of bullet impact and penetration in soft tissue. (Many others have simply assumed that energy is the dominant effect in Wound Trauma Incapacitation; this assumption is even more simplistic than the attempt to actually analyze the dynamics problem with energy relationships, and is no more successful).

Any attempt to derive the effect of bullet impact in tissue using energy relationships is ill advised and wrong because the problem cannot be analyzed that way and only someone without the requisite technical background would try. Many individuals who have not had technical training have nonetheless heard of Newton’s laws of motion, but most of them aren’t really familiar with these laws and would be surprised to learn Newton’s laws describe forces and momentum transfer, not energy relationships. The dynamic variable that is conserved in collisions is momentum; kinetic energy is not only not conserved in real collisions, but is transferred into thermal energy in a way that usually cannot be practically modeled. The energy in collisions can be traced, but usually only by solving the dynamics by other means and then determining the energy flow.

Understanding energy and how it relates to bullet terminal ballistics is useful even though energy is not a useful parameter in most small arms ballistics work.”
It's not that energy is not a valid evaluative measure- it's just that it is so darned hard to use it in this role.
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Old September 25, 2012, 06:50 PM   #68
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155 grain Speer Gold Dot = 496 ftlbs

Quote:
But since it this is made up, it really doesn't mean anything. And how do you come up with this sort of notion? Do you have any evidence to support this conjecture? Can you cite any authority to support it. As the experts I quoted in post 52 point out, the energy doesn't create the damage.

Your fundamental premise is fallacious.
The numbers were made up to illustrate my point, nothing more.

What do you mean where do I come up with such a notion? Work can't be done without energy, period. That is elementary school level science. A bullet in motion has a given amount of energy. That is also elementary school level science. The variables are where and how that energy is used. That is common sense. Some of the energy is used to displace air on the way to the target. Some is used penetrating, damaging, and moving the target. Some is often used behind the target.

The part we care about, the part used effectively, is the part used penetrating and damaging the target. That damage cannot occur without the energy to do it and all the energy in the world does no good behind the target. That is why we don't normally use fmj bullets to hunt with. There is nothing fallacious or "out of the box" about this. It is basic science and common sense.

Let me try phrasing this another way. The bullet does work because it possesses energy. Without that energy, it cannot do the work. Likewise, whatever work is done on anything other than damaging the target, is usually of little or no use.

Quote:
It's not that energy is not a valid evaluative measure- it's just that it is so darned hard to use it in this role.
I agree with to some extent. The problem with using any one thing is that there are still other variables and they greatly effect the amount of damage done.
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Old September 25, 2012, 07:55 PM   #69
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As I understand it, energy that creates a temporary cavity is often ineffective, because elasticity of tissue may often allow tissue to stretch beyond the temporary cavity without taking major damage.

Most handgun rounds do not have the energy to exceed such limits (unlike most rifle rounds, which can really tear things up). So, energy that does not directly contribute to creating a permanent wound channel may merely be expended without lasting effect.

Also, while energy is required for work, penetration is affected more by momentum, sectional density, and bullet type.

Last, those handgun rounds which can reach levels of energy that can really do extra damage, typically are hard for the average shooter to control - and the average shooter may not be willing to practice enough to get a good hit with the first shot.

Even good shooters will have a harder time with follow up shots with heavy magnum type loads.
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Old September 25, 2012, 08:52 PM   #70
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MLeake, good post.

I will add a few comments here for the sake of clarity.

A temporary cavity is not what I consider damage. I am not going to say it is of no value since I believe there is value in pain. How much is debatable and I certainly wouldn't put faith in it. Damage is obviously needed to cause incapacitation.

I agree that momentum is generally a better indicator of penetration in soft tissue. Hard barriers are a different issue. Again, it goes back to how much of the energy is used effectively.

I also don't disagree in regards to shootability, especially in regards to small easily concealed handguns. Every firearm is a compromise and that is certainly true of handguns. That is a different question though.
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Old September 25, 2012, 10:30 PM   #71
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From Frank:

Quote:
The error is to focus on energy. A suitably effective cartridge will have adequate energy. But it is not the energy that is causing the cartridge to be effective; it is not the energy causing the damage (at least at the range of velocities of handgun cartridges customarily used for self defense). It is the combination of factors resulting in a bullet of large enough diameter penetrating deeply enough; the necessary tissue damage is caused by the penetration of the bullet.
Sometimes when trying to explain something we get our feet tangled and trip up, maybe that's what happened above.

Energy does not do the damage either in handguns or rifles, the bullet does the damage in both. Energy has neither weight nor mass so in and of itself it can do no damage. There are no energy beams at present.

We all know that the faster we get a bullet going the more potential damage that bullet can do. It doesn't matter the caliber or the mass as long as the bullet is a good one for the speed it's going and built right for the job the faster one has the potential to do more damage once it strikes.

But why? Simply because what ever it hits can't get out of the way fast enough. The bullet pushes it's way through flesh and bone, tearing and disrupting tissue as it goes. As it expands, providing it does, the amount of disruption increases. At lower velocities the amount of damage is usually limited to the area right around the bullet's path. At higher velocities the damaged area can be several times larger. I've seen wounds where bone has been cracked and a neat hole punched through from a 45 Colt. I've also seen wounds in deer and hogs where sections of flesh were liquified and the bone splintered and fractured from high velocity rifle rounds.

In general the faster we get a round going the more damage it can potentially do. There are other factors involved of course, a .22 l.r. round will not do as much damage as a 38 Spl. even though it is faster.

The energy figures we use, so many foot pounds, etc., measure the potential for the bullet to do it's work. But in and of itself the energy does no damage. The bullet does the damage.

Energy cannot be destroyed only transferred. As the bullet travels down the muzzle, through the air, penetrates, expands, etc. it sheds energy. Transfers it, mostly into heat, the bullet utilizes the energy to do it's work. All bullets do this. A .45 acp at 860 fps does it as much as a 30-06 round at 2800 fps. They both utilize energy to do their work and because one has a good deal more energy than the other it can do it's work over a longer distance and do more damage once it gets there. It has more energy, in this case, because it's faster among other things.

We've known this since we were kids and throwing rocks. We observed all this then. We threw rocks in lakes and puddles, into mud and watched the results. We debated the merits of cinder blocks, vs. bricks, vs. a good hard round stone from a stream, vs. a dirt clod.

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Old September 25, 2012, 10:35 PM   #72
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Go read my post on the first page...
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Old September 25, 2012, 10:38 PM   #73
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Quote:
I will say this, from my observations, I elect to use the .44 caliber Remington Semi-Jacketed Hollow Point bullet as my personal defense selection.

I have observed its effect on animate tissue loaded in the .44 Magnum. So, I elect to use it in my .44 Special. Until I'm proved wrong in actual practice, this will be my choice for daily carry.
If a fella takes a round designed to work well for the velocities of the 44 Magnum and loads them to the velocities of the 44 Spl. the bullet may not work as well or as intended. What will expand at 1300 fps likely will not expand at 900. It may be useful to experiment some.

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Old September 25, 2012, 10:57 PM   #74
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Quote:
Originally Posted by SRH78
...Work can't be done without energy, period. That is elementary school level science. A bullet in motion has a given amount of energy. That is also elementary school level science. The variables are where and how that energy is used. That is common sense....
Quote:
Originally Posted by tipoc
...We all know that the faster we get a bullet going the more potential damage that bullet can do. It doesn't matter the caliber or the mass...
But this all goes beyond common sense notions. The physics and physiology of bullet performance are much more complex than that.

Look again at post 67 with 481's quote of Duncan MacPherson (with my emphasis added to the McPherson quote);
Quote:
Originally Posted by 481
From the perspective of evaluating/determining which factor is most important in terminal ballistics, I think that Duncan MacPherson, one of my favorite authors on the topic, nails it pretty well here-

Excerpt from "Bullet Penetration"
Quote:
“. . . every now and then someone wants to analyze or think about a problem involving energy, and when they attempt to do this without really understanding energy or other thermodynamic concepts the result is unfortunate. One such problem is the analysis of any of the various aspects of terminal ballistics; some individuals with inadequate technical training and experience have unwisely and unproductively attempted to use energy concepts in the analysis of bullet impact and penetration in soft tissue. (Many others have simply assumed that energy is the dominant effect in Wound Trauma Incapacitation; this assumption is even more simplistic than the attempt to actually analyze the dynamics problem with energy relationships, and is no more successful).

Any attempt to derive the effect of bullet impact in tissue using energy relationships is ill advised and wrong because the problem cannot be analyzed that way and only someone without the requisite technical background would try. Many individuals who have not had technical training have nonetheless heard of Newton’s laws of motion, but most of them aren’t really familiar with these laws and would be surprised to learn Newton’s laws describe forces and momentum transfer, not energy relationships. The dynamic variable that is conserved in collisions is momentum; kinetic energy is not only not conserved in real collisions, but is transferred into thermal energy in a way that usually cannot be practically modeled. The energy in collisions can be traced, but usually only by solving the dynamics by other means and then determining the energy flow.

Understanding energy and how it relates to bullet terminal ballistics is useful even though energy is not a useful parameter in most small arms ballistics work.”
It's not that energy is not a valid evaluative measure- it's just that it is so darned hard to use it in this role.
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Old September 25, 2012, 11:22 PM   #75
JohnKSa
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Quote:
But it is not the energy that is causing the cartridge to be effective; it is not the energy causing the damage (at least at the range of velocities of handgun cartridges customarily used for self defense).
Since kinetic energy is, according to established science, the potential of a projectile to do work, it is not possible to say that kinetic energy does not cause damage since, effectively, damage is equivalent to the work done on the target medium by the projectile.

Kinetic energy causes damage any time a moving projectile causes damage. Does it tell the whole story? No, and it can be difficult to use energy to make relative assessments of the performance of rounds that differ significantly in other respects, but it's important not to wander too far afield of what science tells us about what kinetic energy means.
Quote:
The physics and physiology of bullet performance are much more complex than that.
That is true, because kinetic energy is only a measure of potential, not a measure of what will happen, because some of the work done by the projectile may not have any significant wounding effect (e.g. temporary cavity in elastic tissues), and because phsyiology is tremendously complex. However, neither the fact that kinetic energy doesn't tell the whole story, nor the fact that the problem of terminal ballistics is very complex, can justify an attempt to redefine kinetic energy by stating that it doesn't cause damage.
Quote:
...kinetic energy is not only not conserved in real collisions...
This statement may be somewhat misleading to some. It is true that kinetic energy is not conserved, but overall energy is certainly conserved, and many of the energy conversions have significant effects on the target medium in one form or another. In fact, any movement of the target medium or damage to the target medium is the result of an energy conversion of one sort or another.
Quote:
Energy does not do the damage either in handguns or rifles, the bullet does the damage in both.
Without kinetic energy, the bullet does not move and therefore it does no damage. Only moving projectiles can cause damage, and therefore it's not possible to dismiss kinetic energy as a factor in the damage caused by moving projectiles.

There are two major misconceptions about kinetic energy when it comes to terminal ballistics.

1. Kinetic energy tells the whole story.
2. Kinetic energy doesn't have anything to do with the answer.

Neither is true.
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