When deciding between sizes and velocities of self-defense ammo, should I base my choice on the highest relative KINETIC ENERGY between two rounds, or the highest relative FOOT POUNDS of ENERGY? In other words, which definition of energy is most useful for choosing a self-defense cartridge? And why?
Kinetic Energy or Ft Pounds Energy...?
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Naterstein
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I am not a physicist nor a ballistician, but I think they are one in the same in the world of ballistics and how they are calculated. At least Ft lbs AFAIK is calculated as grains*velocity.
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warrior poet
New member
Kinetic energy calculations favor light bullets however. The formula is KE = 1/2 mass * velocity squared. Since momentum is just mass * velocity, heavier projectiles resist acceleraton (or deceleraton... or wind deflection) and momentum is "... object in motion will stay in motion unless acted upon by an outside force..." to quote the good Mr. Newton.
All the math in the world is moot, however, if you miss.
All the math in the world is moot, however, if you miss.
I THINK what the OP is getting at is actually momentum VS kinetic energy.
Momentum favors heavier bullets, while Kinetic Energy favors lighter, faster bullets when each is fired from the same cartridge at the same pressure levels.
Deciding which school of thought is "better" requires one to first decide what they expect from the chosen bullet/load.
When in "urban" areas, I usually carry a lighter, faster, hollow point bullet (but not too light) to minimize over-penetration should I need my firearm in areas with people. I'm always careful about what's behind what I'm shooting at, but this would seem like a wise preventative measure to me.
When in more "rural" areas, over-penetration becomes a non-issue for the most part, so I usually carry heavier bullets. Out in the hills, I want more penetration in a general purpose carry load. For this purpose, a heavy-for-caliber cast bullet is about as good as anyting else, and perhaps better.
It all depends on what you want from your load, but don't get too carried away with "energy" figures. Energy is nothing more than a mathmatical formula made up by scientists, and it doesn't kill a thing. It's only a way of measuring the force of an object in motion, and it's flawed for measuring the ability of a bullet to damage internal organs and tissue.
Daryl
Momentum favors heavier bullets, while Kinetic Energy favors lighter, faster bullets when each is fired from the same cartridge at the same pressure levels.
Deciding which school of thought is "better" requires one to first decide what they expect from the chosen bullet/load.
When in "urban" areas, I usually carry a lighter, faster, hollow point bullet (but not too light) to minimize over-penetration should I need my firearm in areas with people. I'm always careful about what's behind what I'm shooting at, but this would seem like a wise preventative measure to me.
When in more "rural" areas, over-penetration becomes a non-issue for the most part, so I usually carry heavier bullets. Out in the hills, I want more penetration in a general purpose carry load. For this purpose, a heavy-for-caliber cast bullet is about as good as anyting else, and perhaps better.
It all depends on what you want from your load, but don't get too carried away with "energy" figures. Energy is nothing more than a mathmatical formula made up by scientists, and it doesn't kill a thing. It's only a way of measuring the force of an object in motion, and it's flawed for measuring the ability of a bullet to damage internal organs and tissue.
Daryl
christcorp
New member
Daryl is correct. What is important; in my opinion; is RETENTION. With the lighter bullet, obviously at higher speeds, there is going to be a higher amount of energy (Ft/Lbs) than with the heavier. However, that is ONLY at the point of impact. In other words, lighter bullets, even though they start off with more energy, will dissipate that energy faster than a heavier bullet. The heavier bullet will retain the energy longer, and thus allow for more/deeper penetration.
Of course, if you get a high enough velocity, you can make up for the lighter bullet. But then again, the velocity could be so high that the round would be uncontrollable. So, when doing your research, look for penetration tests. 2 bullets with the same exact depth of penetration, favors the larger caliber, because it's creating a larger hole. Thus, more blood loss and greater chance of hitting a vital area. When the velocity is close to the same, the heavier/larger bullet will have the greater penetration.
Again, don't worry about ft/lbs (energy). The lighter bullet could have more, but is it going to dissipate that energy too quickly and not allow for adequate penetration??? Look for penetration tests. The more penetration, the better. (Of course unless it's almost guaranteed to exit the body. Like a 44 magnum). But besides that, look at penetration. Not energy and not velocity. 12-16 inches. Then, look for the largest diameter bullet that you can shoot comfortably. (If you're buying your first gun).
Of course, if you get a high enough velocity, you can make up for the lighter bullet. But then again, the velocity could be so high that the round would be uncontrollable. So, when doing your research, look for penetration tests. 2 bullets with the same exact depth of penetration, favors the larger caliber, because it's creating a larger hole. Thus, more blood loss and greater chance of hitting a vital area. When the velocity is close to the same, the heavier/larger bullet will have the greater penetration.
Again, don't worry about ft/lbs (energy). The lighter bullet could have more, but is it going to dissipate that energy too quickly and not allow for adequate penetration??? Look for penetration tests. The more penetration, the better. (Of course unless it's almost guaranteed to exit the body. Like a 44 magnum). But besides that, look at penetration. Not energy and not velocity. 12-16 inches. Then, look for the largest diameter bullet that you can shoot comfortably. (If you're buying your first gun).
Actually, momentum favors mass and velocity equally (the formula is mass times velocity) while energy favors velocity over mass (the formula is mass times velocity squared). Doubling the velocity of a bullet will have the same effect on momentum as doubling the mass, but doubling the velocity will cause an exponential increase in energy while doubling the mass will not.
As to energy vs. momentum vs. whatever with regards to what makes a bullet effective, it's all about balance. Kinetic energy can contribute to effectiveness, but only if adequate placement and penetration are already present. Temporary cavitation, which is almost directly correlated with energy transfer, can cause significant damage to certain tissues. The problem is that it does not cause significant damage to other tissues and in the stress of a gunfight, one cannot guarantee which organs a bullet will strike. The problem with many loadings with a lot of kinetic energy is that either they achieve it by driving very light-for-caliber bullets at very high-for-caliber velocities and don't penetrate well or the recoil is so excessive that the shooter cannot shoot accurately. In my opinion, the more kinetic energy the better so long as placement and penetration are not sacrificed in order to get it.
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High velocity rounds have the characteristic of imparting hydrostatic shock, and transferring a greater proportion of their energy to a wet target as collateral damage, instead of just passing through it. Even a flat pointed bullet, at high velocities, sprays water and tissues sideways with greater energy at high velocity than it does at lower velocities.
A KE figure that is high will normally designate a round as being damaging. The same type of round with a momentum figure that is more in line with the KE will generally be a penetrating round. Until you complicate things by adding in bullet performance. The really old style military rifle rounds that fired such things as 180 grain round tipped FMJ did little damage, as their design didn't allow for much energy transfer. the round tips would drill through the person, leaving small wounds. (the mauser spitzer points changed that.) Switching that round tip ball load for a modern soft point made a cartridge that was far more effective at transferring KE, and also, coincidentally, more effective at damaging tissue and wounding.
What really matters, isn't KE or momentum, what matters is that you have an effective bullet and a velocity that is high enough for it to perform.
Strip a 9mm NATO round of it's ball projectile and add a top grade hollow point, and you will turn an inefficient round into a top grade killer.
One thing that you have not considered is a very important factor, sectional density. SD is basically the amount of weight contained within the area taken up by a bullet's base. in a 9mm load, you will get very little penetration with a 100 grain bullet at extreme velocity, as it lacks momentum, and the KE is used up displacing and damaging tissues in the early stages of penetration. A 158 grain .38 is a far denser bullet, and isn't usually loaded to the velocity levels KE is relevant. It will, however, penetrate deeply.
As I read this, it seems rather confusing and disjointed.
Essentially, forget the energy numbers. Choose by caliber, bullet weight, bullet construction, and velocity.
Are you looking for a deep wound? heavy bullets for that caliber, controlled expansion bullets, and moderate to high velocity.
Do you want lots of damage and minimal penetration or retained energy after ricochet? Light bullets for that caliber, frangible or extreme expansion hollow points, and the highest possible velocity.
http://www.youtube.com/watch?v=sYigC49tnh8&feature=player_embedded
A perfect way to see what the KE measure is all about is to view this video. The bullet is the same weight, for all practical purposes, as a .22 LR. Cranked up to almost 4,000 fps, The amount of energy transferred to the target by that frangible bullet is astonishing. even the hottest .22 LR hollow point will only shatter and break up an apple; this sort of load and KE levels liquefy them.
A KE figure that is high will normally designate a round as being damaging. The same type of round with a momentum figure that is more in line with the KE will generally be a penetrating round. Until you complicate things by adding in bullet performance. The really old style military rifle rounds that fired such things as 180 grain round tipped FMJ did little damage, as their design didn't allow for much energy transfer. the round tips would drill through the person, leaving small wounds. (the mauser spitzer points changed that.) Switching that round tip ball load for a modern soft point made a cartridge that was far more effective at transferring KE, and also, coincidentally, more effective at damaging tissue and wounding.
What really matters, isn't KE or momentum, what matters is that you have an effective bullet and a velocity that is high enough for it to perform.
Strip a 9mm NATO round of it's ball projectile and add a top grade hollow point, and you will turn an inefficient round into a top grade killer.
One thing that you have not considered is a very important factor, sectional density. SD is basically the amount of weight contained within the area taken up by a bullet's base. in a 9mm load, you will get very little penetration with a 100 grain bullet at extreme velocity, as it lacks momentum, and the KE is used up displacing and damaging tissues in the early stages of penetration. A 158 grain .38 is a far denser bullet, and isn't usually loaded to the velocity levels KE is relevant. It will, however, penetrate deeply.
As I read this, it seems rather confusing and disjointed.
Essentially, forget the energy numbers. Choose by caliber, bullet weight, bullet construction, and velocity.
Are you looking for a deep wound? heavy bullets for that caliber, controlled expansion bullets, and moderate to high velocity.
Do you want lots of damage and minimal penetration or retained energy after ricochet? Light bullets for that caliber, frangible or extreme expansion hollow points, and the highest possible velocity.
http://www.youtube.com/watch?v=sYigC49tnh8&feature=player_embedded
A perfect way to see what the KE measure is all about is to view this video. The bullet is the same weight, for all practical purposes, as a .22 LR. Cranked up to almost 4,000 fps, The amount of energy transferred to the target by that frangible bullet is astonishing. even the hottest .22 LR hollow point will only shatter and break up an apple; this sort of load and KE levels liquefy them.
KE, hammer time...
To me, KE is very important for a carry/protection/duty handgun round.
About 3 years ago, I saw a old VHS firearms training video during my security re-qual where the video host/instructor went on a jag about how KE is not a factor.
His reasoning to me was flawed and invalid. The host said speed & vel that pushes a bullet deep into a target(penetration) is better than a powerful round with a high KE level.
I disagree. I say a handgun/duty type load should have a high KE level(450-550 ft-lbs) and have a lot of punch. In a real critical event, your goal as a LE/security officer or armed citizen is to stop the threat as quickly as possible. High KE level handgun rounds can create the harder shock or hit to a subject that will disable or wound them faster than a low KE level round that will not cause any shock, hit or punch to the same violent subject.
If you took a Stanley or Craftsman hammer and hit someone on the hand it would be very fast and cause an injury. If you took a sledge hammer and hit someone on the hand the exact same way, it would be slower but would have a higher KE level, hit harder than the Stanley hammer and cause more damage.
I'm not saying every armed citizen or cop should carry a .44magnum or a .50AE Desert Eagle but when selecting a carry or HD sidearm, KE levels should be a factor.
Clyde
To me, KE is very important for a carry/protection/duty handgun round.
About 3 years ago, I saw a old VHS firearms training video during my security re-qual where the video host/instructor went on a jag about how KE is not a factor.
His reasoning to me was flawed and invalid. The host said speed & vel that pushes a bullet deep into a target(penetration) is better than a powerful round with a high KE level.
I disagree. I say a handgun/duty type load should have a high KE level(450-550 ft-lbs) and have a lot of punch. In a real critical event, your goal as a LE/security officer or armed citizen is to stop the threat as quickly as possible. High KE level handgun rounds can create the harder shock or hit to a subject that will disable or wound them faster than a low KE level round that will not cause any shock, hit or punch to the same violent subject.
If you took a Stanley or Craftsman hammer and hit someone on the hand it would be very fast and cause an injury. If you took a sledge hammer and hit someone on the hand the exact same way, it would be slower but would have a higher KE level, hit harder than the Stanley hammer and cause more damage.
I'm not saying every armed citizen or cop should carry a .44magnum or a .50AE Desert Eagle but when selecting a carry or HD sidearm, KE levels should be a factor.
Clyde
Apply the Question to 22Mag...
I'm the OP.
I'm trying to learn about this issue so I can apply it to any of my handguns...22lr, 22mag, 380, 9mm and 357 mag.
But, I guess what prompted the original question was my 2" NAA Black Widow 22mag, which is my go-everywhere-all-the-time-in-my-pocket BUG. For potential SD needs, should I load it with the lightest, fastest 22mags, such as 33 grains, or should I go with the slower, heavier 40 grains? I was wondering which type of energy calculation would help answer the question objectively. For example, using data from somebody else on the forum for 2"" pistol barrel (I forget who or when, I simply jotted down these numbers...)
Winchester Super-X_______40gr FMJ________1005
(Momentum: 40x1005=40,200)
(KE: ½ Mass x V2 = 20.3M)
CCI Maxi-Mag____________50gr GoldDot HP___857
(Momentum: 50x857= 42,850)
(KE: ½ Mass x V2 = 18.3M)
The Winchester 40gr mags have a higher Kinetic Energy, but a lower Momentum calculation.
The CCI 50gr mags have higher Momentum calculation, but a lower Kinetic Energy.
Maybe it doesn't even make any difference. Just hit CNS and be done with it. But, for the sake of conversation...Which would you carry? Lighter and Faster, or Heavier and Slower?
Yeah, I know, a 50 grain Maxi Mag isn't "Heavy"...but, work with me on this!
I'm the OP.
I'm trying to learn about this issue so I can apply it to any of my handguns...22lr, 22mag, 380, 9mm and 357 mag.
But, I guess what prompted the original question was my 2" NAA Black Widow 22mag, which is my go-everywhere-all-the-time-in-my-pocket BUG. For potential SD needs, should I load it with the lightest, fastest 22mags, such as 33 grains, or should I go with the slower, heavier 40 grains? I was wondering which type of energy calculation would help answer the question objectively. For example, using data from somebody else on the forum for 2"" pistol barrel (I forget who or when, I simply jotted down these numbers...)
Winchester Super-X_______40gr FMJ________1005
(Momentum: 40x1005=40,200)
(KE: ½ Mass x V2 = 20.3M)
CCI Maxi-Mag____________50gr GoldDot HP___857
(Momentum: 50x857= 42,850)
(KE: ½ Mass x V2 = 18.3M)
The Winchester 40gr mags have a higher Kinetic Energy, but a lower Momentum calculation.
The CCI 50gr mags have higher Momentum calculation, but a lower Kinetic Energy.
Maybe it doesn't even make any difference. Just hit CNS and be done with it. But, for the sake of conversation...Which would you carry? Lighter and Faster, or Heavier and Slower?
Yeah, I know, a 50 grain Maxi Mag isn't "Heavy"...but, work with me on this!
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I have no references for this, it's just what I've figured out in my head from my engineering training 30 years ago 
Until you get to .357 Magnum and up, go for heavier all the time. 9mm is a special case because it's so small; if you go with too heavy there's not enough room left for powder (so go with kind-of-heavy but maybe not 147's)
Penetration is proportional to the momentum, which is mass times velocity. The energy is 1/2 mass x velocity squared. As the bullet travels, it loses velocity, so it must lose energy. That energy has to go somewhere; it goes into the budguy, and the more energy transferred the more tissue damaged. The lighter bullet has a little more energy to start with and it decelerates faster, so it does more damage. But it's also losing momentum, and if it loses too much momentum it won't reliably penetrate deep enough.
Does that make sense? .357 Magnum, 10mm, .45 Colt, .44 Magnum, etc have enough energy to be penetrate well with light bullets. Lessor cartridges might not. And I've ignored the part about bullet expansion.
Until you get to .357 Magnum and up, go for heavier all the time. 9mm is a special case because it's so small; if you go with too heavy there's not enough room left for powder (so go with kind-of-heavy but maybe not 147's)
Penetration is proportional to the momentum, which is mass times velocity. The energy is 1/2 mass x velocity squared. As the bullet travels, it loses velocity, so it must lose energy. That energy has to go somewhere; it goes into the budguy, and the more energy transferred the more tissue damaged. The lighter bullet has a little more energy to start with and it decelerates faster, so it does more damage. But it's also losing momentum, and if it loses too much momentum it won't reliably penetrate deep enough.
Does that make sense? .357 Magnum, 10mm, .45 Colt, .44 Magnum, etc have enough energy to be penetrate well with light bullets. Lessor cartridges might not. And I've ignored the part about bullet expansion.
Kinetic Energy is a measure of how much work (damage) a moving projectile can do. It relates to the POTENTIAL of a particular round to do damage to the target medium. Whether or not the round lives up to its potential is an entirely different story.
Momentum is a measure of how hard it will be to stop a moving projectile. It relates to penetration in that if you fire two otherwise identical rounds into identical material the one with more momentum will tend to penetrate deeper.
Both quantities are measurable scientific quantities and both are important to understanding the basics of how projectiles behave and what they are capable of. There is much, MUCH more to getting the WHOLE picture and I don't believe anyone really has managed to achieve that level of understanding.
Trying to accurately rank the terminal performance of one round over another based purely on momentum and/or kinetic energy would be very difficult unless they were very similar in ALL other respects.
Momentum is a measure of how hard it will be to stop a moving projectile. It relates to penetration in that if you fire two otherwise identical rounds into identical material the one with more momentum will tend to penetrate deeper.
Both quantities are measurable scientific quantities and both are important to understanding the basics of how projectiles behave and what they are capable of. There is much, MUCH more to getting the WHOLE picture and I don't believe anyone really has managed to achieve that level of understanding.
Trying to accurately rank the terminal performance of one round over another based purely on momentum and/or kinetic energy would be very difficult unless they were very similar in ALL other respects.
ScottRiqui
New member
It's really hard to separate the effects of momentum and kinetic energy because both quantities depend solely on mass and velocity.
In your example of two identical rounds with different momenta, the bullet with the greater momentum will also have the greater kinetic energy. As such, you couldn't attribute differences in penetration solely to the momentum.
An interesting test would be a penetration test involving two different bullets that have the same kinetic energy but different momenta, or the same momenta but different kinetic energies.
cougar gt-e
New member
People say momentum favors mass and they usually are comparing it with kinetic energy.
Yeah, It's M * V so mass and V are equal, but for a constant velocity, adding more mass increases momentum faster than it increases KE which uses V squared.
Also, more massive bullets typically will hold the velocity longer. So a 220gr .45 will slow down more gradually than a 155gr .45. That's important when you need to penetrate something to reach the important bits of the BG.
Still, I'd rather score 5 hits with a .22 short than 10 misses with a .50S&W....
Yeah, It's M * V so mass and V are equal, but for a constant velocity, adding more mass increases momentum faster than it increases KE which uses V squared.
Also, more massive bullets typically will hold the velocity longer. So a 220gr .45 will slow down more gradually than a 155gr .45. That's important when you need to penetrate something to reach the important bits of the BG.
Still, I'd rather score 5 hits with a .22 short than 10 misses with a .50S&W....
christcorp
New member
Brian; you are correct that high velocity rounds can cause hydrostatic shock. But the amount of energy required is usually at the bare minimum of around 550 ft-lbs. Which means that unless the cartridge is a 357 magnum or 44 magnum and bigger; possibly a hot 10mm; the possibility of hydrostatic shock is very rare.
zxcvbob: Not sure if I agree with the thought that penetration is proportional to momentum. A FMJ penetrate more than a holllow point, yet both have the same momentum upon impact. When one expands it takes up more area, thus dissipating said energy, slowing it down, and thus, less penetration. Another example would be to take a baseball bat and jam it into a person's stomach. It doesn't penetrate very well. Now, do it with a Sword. It penetrates quite nicely. So while energy is a factor, it isn't by itself. Some 22LR can have very little momentum, yet because of their velocity and dynamics, can penetrate further than a 45acp.
zxcvbob: Not sure if I agree with the thought that penetration is proportional to momentum. A FMJ penetrate more than a holllow point, yet both have the same momentum upon impact. When one expands it takes up more area, thus dissipating said energy, slowing it down, and thus, less penetration. Another example would be to take a baseball bat and jam it into a person's stomach. It doesn't penetrate very well. Now, do it with a Sword. It penetrates quite nicely. So while energy is a factor, it isn't by itself. Some 22LR can have very little momentum, yet because of their velocity and dynamics, can penetrate further than a 45acp.
Here is a thought. Momentum is well represented by the .44 magnum with a 240 grain lead bullet. Hitting 5 pound steel silhoutte quail with one threw the thing over 20 feet from the 5 foot high stand. it left a smear of lead
a 223 blew a crater in another one almost 3/8 inch deep, and rolled it maybe ten feet.
They are probably pretty equal in KE. As was mentioned before, the magnum was a momentum specialty round that exerted push and penetration. The .223 is a KE specialist round, and that round caused rapid energy dump and damage.
a 223 blew a crater in another one almost 3/8 inch deep, and rolled it maybe ten feet.
They are probably pretty equal in KE. As was mentioned before, the magnum was a momentum specialty round that exerted push and penetration. The .223 is a KE specialist round, and that round caused rapid energy dump and damage.