Is "Muzzle Energy" significant?

[45_auto]

If both bullets mushroom correctly and do not exit the body, the 185 grain bullet will do more damage by delivering an extra 82 ft-lbs of energy.

A Hershey bar contains about 650 ft-lb of energy (210 calories). They're typically divided into 12 little squares. So each square contains 54 ft-lb of energy. If internally delivered energy meant anything, you could do more damage to the bad guy (deliver 104 ft-lbs of energy to his gut!) by giving him a couple of squares of chocolate from a Hershey bar.

Conversion calculator here:

https://www.unitjuggler.com/convert-energy-from-ftlb-to-kcal.html?val=82

 

[B.L.E.]

A Hershey Bar actually has about 650,000 ft. lb. of energy. If a human can convert 30% of that into work, he can use the energy of that bar to do 195,000 ft lb of work, as in a 195 pound man climbing up a 1000 ft high flight of stairs perhaps.
The dietary calorie is actually a kilocalorie.
Kinetic energy is simply the amount of energy it takes to accelerate a bullet to it's muzzle velocity, or roughly how much gunpowder the cartridge will need.

Let's say you have a bow and it takes 50 lb of force to draw it back, if you draw it back 24 inches, you did 100 ft-lb of work to draw it back. That makes the velocity of the arrow the velocity that results in 100 ft-lb of kinetic energy, actually somewhat less since nothing is 100% efficient. But if you did 100 ft-lb of work in drawing back the bow, then 100 ft-lb of kinetic energy will be the upper bound on the arrow's KE.

 

[45_auto]

That's good to know, I'm much less cognizant than I should be of food calories!

Since a typical Hershey bar is 1.55 ounces, that means that I only have to give the bad guy 82 / 650,000 * 1.55 = .0002 ounces of my Hershey bar to deliver the 82 ft-lb of energy to his body.

Since each little square is 1.55 / 12 = .13 ounces, that means that .0002 / .13 = .0015 of a square = 82 ft-lb of energy.

So I only have to give him a little over a thousandth of a single square from my Hershey bar to deliver that devastating 82 ft-lb of energy. I can then deliver the other 649,918 ft-lb of damage from the Hershey bar to my own body.

Do you think it will knock me across the room?

 

[B.L.E.]

A Hershey bar actually has zero kinetic energy. It has about 650,000 ft-lb of potential energy or more accurately, setting fire to it and burning it up will release about 835 BTU of heat. An old timey steam locomotive might be able to turn about 5% of that heat into kinetic energy. Candy is useless as a fuel for guns although there are some sugar based black powder substitutes.

The energy in a candy bar can however be compared to the energy contained in a charge of gunpowder.

A pound of gasoline has about 18500 BTU of heat when burned, but it too is useless as a fuel for guns.
Burn that pound of gasoline in a tractor engine and it could likely be used to do just as much damage to a house as a dozen sticks of dynamite.

 

[45_auto]

A Hershey bar actually has zero kinetic energy.

So it's not potential energy that does the damage, but kinetic energy?

If you're standing in the street and I roll my 5,300 pound Suburban into you at 1 ft/sec (a little less than 1 MPH, actually 0.68 MPH), which gives it 82 ft-lb of kinetic energy, will it do the same amount of damage to you as motorhead0922's .45 Colt 82 ft-lb?

 

[natman]

So it's not potential energy that does the damage, but kinetic energy?

Potential energy does nothing, at least not now. If you have a weight on a high shelf, it has potential energy that would happen if it were to fall to the floor sometime in the future.

Kinetic energy is potential energy realized.

 

[natman]

Energy figures can be misleading. They are OK when comparing similar cartridges, but energy calculations leave out some of the most important factors in a bullets effectiveness: bullet diameter and terminal performance.

A 55 grain varmint bullet from a 22-250 has more energy than a 400 grain softpoint from a 45-70, but I know which one I'd rather have if faced with a charging bear.

 

[mavracer]

If you're standing in the street and I roll my 5,300 pound Suburban into you at 1 ft/sec (a little less than 1 MPH, actually 0.68 MPH), which gives it 82 ft-lb of kinetic energy, will it do the same amount of damage to you as motorhead0922's .45 Colt 82 ft-lb?

No because energy isn't factor in penatration of guns, momentum is and your Burb with 82ft lbs will have way more momentum.
If you make the momentum the same and give your Burb a .452 diameter rod out the crong then make the person stationary then yes they'll do the same damage.
How do you think bullet proof vests work.
Kinetic Energy is blown way out of proportion as to its importance with firearms and soft tissue. Much of work done by KE from the change of form is into heat energy and elastic energy as tissue stretches. Heat doesn't wound and the debate rolls on about temporary wound channel importance.

 

[T. O'Heir]

Nothing will stop a charging griz in his tracks. Physics doesn't allow it. A .45 Colt with any bullet will just annoy him and you will never be fast enough anyway.
However, ME numbers are mostly about having a place to start. The physics says big will have more energy, but velocity matters. Big going fast has more energy that small going fast. So your 360 will have more energy than a 225 at the same speed.
"...a friend and I were chased by a very large brown bear..." Brown phased black bear. No Griz in Easter Canada. Oh and just give him the picnic basket. Shuts him up every time. snicker.

 

[KyJim]

Nothing will stop a charging griz in his tracks. Physics doesn't allow it.

Not necessarily. A broken shoulder bone may drop it pretty close to in its tracks. If it can't bear the bear, the bear can't bear to go on.

 

[mavracer]

A broken shoulder bone may drop it pretty close to in its tracks.

I'm not sure that I can out run a 3 legged bear and I know I can't whip one, but I know a CNS hit will pile up any charge right now. Stay calm and shoot straight

 

[kozak6]

Kinetic energy is directly proportionate to the square of velocity. So, a bullet moving twice as fast as another bullet of the same mass will have four times as much kinetic energy. A bullet moving three times faster will have nine times as much energy.

Or, in other words, small changes in velocity make a big difference in the amount of energy. And dramatically ranging numbers make for much more exciting marketing and discussion.

Although terminal ballistics is a very complicated field with many factors at play, I think bullet momentum is a far more useful measurement. You guys ever look at brassfetcher and such? Unless there's something unusual about bullet construction, bullets of similar momentum even in different calibers tend to have similar wound profiles.

 

[RaySendero]

Saw on another site were someone had posted a cell phone video of a sow charging a group in a raft. Sow had cubs present and charged into the water from the bank. Guide fired one warning shot into the water in front of the Griz. Griz stopped its charge and returned to its cubs. So a loud pistol that made a splash in front of the Griz worked in that situation.

I know for me (and probably for that guide) its easier to carry a pistol, but even though the water slowed the charge some, it still happened pretty fast!
I would prefer to trust a shotgun or a stopper rifle in a Griz charge.

 

[JohnKSa]

Energy figures can be misleading.

It's more accurate to say that energy figures are often misinterpreted. Energy is what it is, and it's not misleading unless it is not understood.

No because energy isn't factor in penatration of guns...

Energy is certainly a factor in penetration. Depending on the circumstances more energy might result in more or less penetration. Assuming similar non-expanding/non-deforming projectiles which remain intact, more energy will result in more penetration. If the projectiles deform/expand and/or do not remain intact, more energy could result in less penetration. It is true that trying to directly relate energy to penetration in the absence of any other information will not be particularly productive.

So it's not potential energy that does the damage, but kinetic energy?

Potential energy is waiting to be converted into some other type of energy. It does nothing until that conversion happens.

Kinetic energy is a physical quantity that defines the potential of a moving object to do work. Whether or not a moving object does all the work that it has the potential to do depends on a number of factors.

Terminal ballistics is very complicated. Trying to boil it down to a single number, or even a couple of numbers is going to result in misleading results and confusion. However even though the basic physics of moving objects doesn't begin to tell the whole story, ignoring, discounting, or misinterpreting any of the quantities that define the basic physics of moving objects (velocity, momentum, energy, mass) will make it difficult to understand the problem.

 

[mavracer]

Energy is what it is, and it's not misleading unless it is not understood.

Here we go again.

Energy is certainly a factor in penetration.

Only when misrepresented like you are doing now.

Depending on the circumstances more energy might result in more or less penetration.

If energy was a factor in penatration then it wouldn't depend on "circumstances".

Assuming similar non-expanding/non-deforming projectiles which remain intact, more energy will result in more penetration.

Not necessarilly, provided energy goes up when momentum does it will, but in cases where you change the mass, the bullet with the most momentum will penatrate more.

 

[JohnKSa]

If energy was a factor in penatration then it wouldn't depend on "circumstances".

If it were “the only” factor then no other circumstances would matter. Because it is “a” factor, instead of “the only” factor, penetration also depends on other circumstances and factors besides energy.

This is what I was referring to when I stated that energy isn’t misleading unless it is not understood or misinterpreted. Believing that energy is the only factor that matters will cause as much confusion about terminal ballistics as believing it doesn’t matter at all, or believing that only momentum matters. Trying to ignore/discount, or overemphasize, any of the quantities of the basic physics of moving objects will result in confusion.

Not necessarilly, provided energy goes up when momentum does it will, but in cases where you change the mass...

Here’s what I wrote: “Assuming similar, non-expanding/non-deforming projectiles…”

You are correct that if you change other variables/factors/circumstances (such as the mass of the bullet) then it is no longer possible to state what will happen based purely on changes in energy.

… in cases where you change the mass the bullet with the most momentum will penatrate more…

It is true that if one manages to keep all other factors/variables constant and increases momentum by changing ONLY the mass of the bullet, that will result in increased penetration.

However, in the general case it is more complicated.

For one thing, momentum depends on BOTH mass and velocity and if momentum is increased by increasing velocity, it can actually result in decreased penetration if expanding/deforming projectiles are involved and the projectile “fails” or over-expands as a result of the increased velocity/momentum.

It is also true that if one compares two bullets with different frontal areas or even different profiles, the one which offers the most resistance as it passes through the target medium can penetrate less even if it has more momentum.

As with energy, momentum is “a” factor in penetration, not “the only” factor and one must consider the other factors in addition to momentum (and energy) to have any chance of understanding the basics.

Momentum and energy reflect two different, but related, properties of moving objects. Momentum is a measure of how hard it is to stop a moving object while kinetic energy is a measure of the potential a moving object to do work.

 

[TXAZ]

T O noted

Nothing will stop a charging griz in his tracks. Physics doesn't allow it.

I'll take that bet. A headshot with a .50 BMG @ 100yards delivers about 10,000 ft lbs of (virtual) explosive energy when it hits a thick Grizzly skull. The impact area of the skull becomes internal shrapnel.
It's no longer on YouTube but I believe the video is still out there, where the shot is fired, and the bear drops immediately.

 

[745SW]

The heavier bullet with a substantially reduced charge will give more felt recoil IMO.

 

[mavracer]

For one thing, momentum depends on BOTH mass and velocity and if momentum is increased by increasing velocity, it can actually result in decreased penetration if expanding/deforming projectiles are involved and the projectile “fails” or over-expands as a result of the increased velocity/momentum.

It is also true that if one compares two bullets with different frontal areas or even different profiles, the one which offers the most resistance as it passes through the target medium can penetrate less even if it has more momentum.

Of course the diameter of the permanent wound channel will affect the depth, but again this works in a linear progression not exponentially.
So ultimately even taking expansion into account as long as frontal area is equal the bullet with more momentum will penatrate deeper, Now when both energy and momentum go up then of course so will penatration so as long as you keep it to only those situations it looks like energy is a factor.

Momentum is a measure of how hard it is to stop a moving object

This make me laugh you get this and still don't understand.
The momentum of the bullet is stopped directly by the tissue directly in it's path (permanent wound channel) energy does work (changes form into heat energy, elastic energy)

Energy is a factor in wounding and of course it exists but it is not the factor or a factor that is responsible for the permanent wound volume which includes the actual penatration depth.

 

[JohnKSa]

This make me laugh you get this and still don't understand.
The momentum of the bullet is stopped directly by the tissue directly in it's path (permanent wound channel) energy does work (changes form into heat energy, elastic energy)

I do understand. I'm not trying to say that momentum is not A factor in penetration, just pointing out that it's clear that other factors such as bullet profile, frontal area, energy and expansion also relate to how much a bullet penetrates. It's not exclusively dependent on momentum.

Energy ... is not the factor or a factor that is responsible for the permanent wound volume which includes the actual penatration depth.

Because energy and momentum are both exclusively dependent on mass and momentum, they are essentially two sides of the same coin. It is not possible to completely exclude energy as being a factor in penetration or in permanent wound volume.

For example, the fact that energy is strongly correlated with bullet expansion, which is one of only two factors in permanent wound volume (expanded projectile diameter & penetration depth) makes it clear that energy does affect permanent wound volume even if one is under the misconception that it does not affect penetration at all.

It is also true that expansion has an effect on penetration which means that energy can affect both penetration or expansion

This make me laugh...

If you want to really be amused, here's a joke for you.

You believe that increasing momentum increases penetration but that energy is not a factor in penetration. So try this experiment. Try to increase the energy of a projectile without changing the momentum of the projectile.

Clearly increasing one increases the other. In other words, if changing momentum affects penetration then changing energy must change it as well since changing energy also changes the momentum and vice versa.

This gets back to my original comment: Trying to boil terminal ballistics down to a single number, or even a couple of numbers is going to result in misleading results and confusion. Even though the basic physics of moving objects doesn't begin to tell the whole story, ignoring, discounting, or misinterpreting any of the quantities that define the basic physics of moving objects (velocity, momentum, energy, mass) will make it difficult to understand the problem.