I posted this over on the Handgun Reloading Forum, but thought it might also be a good idea to post it here as well. What is the formula for calculating energy foot pounds of a load? I know it has to do with velocity and bullet weight. I would like to know how much "thump" I am getting. Thanks!

Just click on this link and fill in the blanks and it will calculate it for you:

http://www.ballistics101.com/muzzle_energy_calc.php

Excellent info. VERY useful. THANKS!

A foot pound is the amount of energy required to lift a pound by one foot.

Your 2000 foot pound load has enough energy to move a ton upward by one foot.

I use this formula.....

Bullet weight x velocity x velocity ÷ 450240

Example... 300 x 2750 x 2750 ÷ 450240 = 5038 foot pounds.

Somebody is going to ask why the 200 pound deer didn't fly ten feet.

Yup! Lousy measure of lethality. I'm glad all the really big game animals I've killed with handguns don't know that my chosen firearms don't produce enough "energy" to really kill them - haha!

Thanks Elks.

I have the equation for converting CUP to PSI - courtesy of Mr. Denton
and
the equation to determine Bore Capacity.


I have LOST & forgotten that equation. I'm putting it in My Phone Reminder Page.
Thnx

Jerry

BECAUSE the 200 lb deer BODY did not TRAP all the E. --> simple grin

Jerry

Elkster's formula.

I don't hunt cape buffalo with a Daisy Red Ryder or even a .22 LR....someplace/somewhere foot-pounds of energy does play a role in the equation. Yes, it's not everything.....but it does have a place in the scheme of things.

The food-pound theory of ballistic energy is NOT a real-world way to judge power and suitability of bullets to kill larger and large game
As an example a 22-250 with a 55 grain standard cup and core bullet has the same number of "foot pounds" of energy (1751 Ft Lbs published) as a 45-70 with a 400 grain had cast bullet (1748 Ft Lbs)
So if foot pounds were an accurate way to make comparisons we'd see the same amount of ballistic damage done by both the 22-250 and the 45-70 on a 2000 pound buffalo with a shoulder bone shot.

But we don't.

In fact the 22-250 with frangible 50 and 55 grain bullets will sometimes not exit a coyote. I know because I have killed a few hundred with 22-250 loads in my life.
I seriously doubt anyone would think a 45-70 with any 400 grain bullet could be stopped by a coyote. Cast hard, such bullet shoot clear through bull buffalo and often do it lengthwise. Yet the 45-70 has the same number of foot-pounds.

Using a different way to calculate ballistic energy that also considers diameter into the mix (diameter is what is obtuse to any bullet's direction of travel, so the larger diameter the bullet the more tissue it's striking and moving out of it's way) is to multiply diameter by weight by velocity at impact and divide by 7000 (7000 is used because we enter our weight in grains and one grain is 1/7000 of a pound)

So .224 X 55 X 3700 FPS = divided by 7000 = 6.512 We could call that 6-1/2 as a number for comparison
A 30-06 with a 150 grain bullet would be .308 X 150 X 2900 = divided by 7000 = 19.14 Lets just call this 19.
A 338 Win mag with a 250 grain bullet is .338 X 250 X 2650 = divided by 7000 = 31.23 Say... 31-1/4
A 9.3X62 with a 286 grain is .966 X 286 X 2400 = divided by 7000 = 35.88 Very close to 36
A 45-70 with a 400 grain at black powder speeds is .458 X 400 X 1275 = divided by 7000= 33.36 We could say 33-1/3
A 45-70 with the same bullet shot at 1800 FPS in a strong modern rifle .458 X 400 X 1800 = divided by 7000 = 47.10

Both the 22-250 and the 45-70 have the same number of foot pounds, but figured out this way the 45-70 with the slow black powder load has a factor of 33.3 and the 22-250 is a 6.5.

That is a whole lot closer to the real world.

The down side to this math is that all bullets would have to be of the same construction and act the same way on impact and they clearly are NOT the same, so using correct bullet for the game at hand is quite important, but that is neither here nor there when it comes to comparison ballistic power of a cartridge. That issue is more about energy use, not amount of energy in motion.

Yup, it sells ammo. I've been fighting with the establishment and conventional wisdom over the lack of terminal goodness (this is a technical term) produced by the revolvers I hunt with very publicly over articles, etc. It may be a useful tool when comparing one load to another, or it might not. A .22-250 generates (actually calculates) more energy than my .500 JRH buffalo loads yet there is no denying which is better for a large bovine.

Clearly you will not be using a BB gun or a .22 on Cape buffalo...

Elkhunters formula gets the units correct.

Bullet weight (in grains) X Velocity (in Feet per second) Squared / 450240.

Same formula works for arrows and any projectile weighed in grains and measured in Feet per Second.

Example: 2700 fps x 2700 fps x 130gr / 450,240 =2105 ft/lb

But why doesn’t it, I hit a 145lb deer with a 450 Marlin load that went in the chest and lodged in her ass, she simply fell down. It didn’t lift her at all?

Sounds like a useless figure for hunting, maybe I will ask Mr. Owl

I know from martial arts that energy can keep going even when the projectile has stopped, I’ve seen folk bust several boards but never crack board number one.

This stuff is in the rehlm of Quantum Physics

It's in another realm alright.

? Really ?

My bad, divide by 450240.

Check.

Might be useless, but Colorado uses it to determine the legality of hunting rifles. 1000 ft lbs at 100yards for rifles and 500 ft lbs at 50 yards for handguns.If you all think it is meaningless,try arguing with a game warden when you are using a .357 mag handgun

Just to be a nit picker......
The divisor 450,240 was change back in the late 60's or early 70's to 450,400. Apparently a group of physicists determined the results of using the earlier number didn't quite line up with some newer or more complete observations. Or so I was told a physics professor in college.
The difference in the end result, at least as far as we're concerned, is extremely small...about 1 foot pound with a 30/06 180 grain factory load.

You're Jwall.

He probably owes you a refund on at least part of your tuition. There is no one person, entity, or group who decides on the value of that constant,-- it is the combination of two other numbers, one of which is well defined and the other is pretty well defined, sorta.

Kinetic energy is 1/2 m v^2. To get it in ft-lbs, you have to divide by 7000 to convert grains to pounds, and you have to divide by the acceleration due to gravity to get from slugs to foots. Standard gravity is about 32.17405 ft/sec^2, although it actually varies from place to place.

So, 2 x 7000 x 32.17405 = 450,436.7

But, feel free to use anything close that you can remember. As noted, it doesn't change the result very much. But if you remember what the number is and why it is, then you can easily get the exact number anytime you want it.

Enjoy,

In the formula E=MC2 the "C" stands for velocity of light in meters per second. (300,000,000) and "M" is for mass in the metric system. This is difficult to apply in the English system but E=1/2KMV2.....here the "M" is for mass but the unit of mass in the English system is a slug.....or 32 pounds.

If we are to use grains and feet per second then we convert the "M" by dividing by 32 and again by 7,000 (number of grains in a pound)

because the constant "K" is 1/2 we again multiply like this.....7,000 X 32 X 2 = 448,000

Assuming a velocity of 3,000 feet per second (squared) we get 9,000,000 and times the weight of the bullet (lets assume 150 grains)
we get 3,000 X 3,000 X 150 = 1,350,000,000 Divide that by the 448,000 we get 3,013.3928 foot pounds.....check this with the 150 grain load of a .30-06

The previous number used (450,240) is likely a tad more accurate as the numbers I used are very slightly rounded but are close enough for the kind of girls I go out with.

Why Yes, I am !

How many foot lbs of energy does a 3 ounce scalpel moving 1" every minute have?

NONE, if I get my 40 out quick enuff.


just joking fellows.

Jerry

CUP and PSI are two different things and there IS NO FORMULA to convert one to the other.

Mr Denton has done a pretty fair job of estimating one in terms of the other over a short range and I congratulate him for the effort. He's fairly close....but again over a short range.

I been killin' pigs with 35 fpe? How is that possible?

Long day for me today.

"You're welcome Jwall" is what I should have wrote.

What are you using?.....

Well.....just tell Mr Denton there is no equation.
It’s not mine.


Jerry

Contender carbine, .22 short match chamber, CB shorts.

You are quite correct. The conversation with him was at his loading bench and we were discussing the various formulas for finding FPE. I mentioned that I had been using the 450240 number when he stated the more accurate formula as being 450400. He went on to explain in much greater detail on the math using, iirc, in very similar details as you mentioned and the reasoning for the change in formula which I have long since forgotten.
His final comments on the issue was to simply to round it off to 450400---it was more than close enough for the purposes at hand and that if anyone thought FPE was an accurate measure of killing/stopping power that they needed to get a hell of a lot more real world experience.

I salute you sir.....you're a better hog killer than me.....

200 lb Deer??!! Where?? Certainly not in Texas.

I lift several pounds “per foot” with every step.

-blush-

Not that tough. Cover is dense, shots very close. Little bit of camo and move like smoke is all it takes.

0.224 x 55 x 3700 / 7000 = 6.512
0.355 x 147 x 990 / 7000 = 7.380

And today I learned a subsonic 9mm load is a more effective round than a .22-250!

There is one thing I’ve learned thru all this .....

There are NOT 3 correct answers to 1 question.

Ain’t no thang to me. I shoot rifles with MORE than ‘enuff’

I won’t be UNDER gunned ! .

Jerry

I'm glad all the animals I've shot aren't into physics, especially the ones I've used a big and relatively slow bullet on.

To be fair, in all that shooting, I have noticed that deer seem to be more susceptible to fast and somewhat frangible bullets. I tend to go slightly towards the heavy side with a bullet to avoid excessive damage, though.

You and he are entirely correct about it not being a good indication of stopping power, but it is available and advertised, so it winds up being used for comparisons. As saddlesore mentioned, Colorado specifies downrange energy as a criterion for legal taking methods. Actually, I often use 450,400, because I tend to remember the product of g and 7000 as 225,200, apply the 2 and get your number. Whatever works....

All of that and I’ve seen 243’s drop game harder than a 7mm mag

Really ?
That’s different from my experience. ? Maybe the 7s bullets were too tough ?
Don’t know, am not arguing.

Jerry

Will the same energy lift 1# 2000'?

theoretically.....yes

I don't know the veracity of the story, but an old hunting pard told me of the time he stumbled onto the "deer cave". You know, that haven where all the deer run and hide in upon hearing the first shots fired on opening day. He said he saw charts tacked on the wall showing the ballistics of all cartridges known to to be favored by hunters, including foot pounds of energy and clinical descriptions of wounds inflicted by all the offerings of the bullet manufacturers at the time. Evidently the wise old bucks held classes for the youngsters, to while away the days until it was safe to go back outside again. One thing that struck him, he said while lifting the sixth shot of Wild Turkey to his lips, was the big warning in red hanging over all those charts, graphs and 8x10 glossy color photographs, that cautioned the herd to be extra vigilant about hunters from the 24HCF sneaking around the woods.

I was matching the duffer shot-for-shot, so I didn't much care if he were bullshitting me or not...

Now, THAT’s a good one. 😂😂. Being able to laugh at ourselves is healthy.😄

A Toast to gnoahh !

Jerry

I've heard rumors about that for quite awhile, thanks for the confirmation. Rumored that pigs were doing the same, but since their vision is not so good they were using braille read with their nose.

It did if, the shooter was using one of Bullets that “comes from untogether” upon impact, that so many people seem to favor these days! memtb

Steve,
This is in reply to your post, but ran on and is not aimed
to insult you.

I think these things go on because one side worships FPE,
and the other discounts it.

They are both wrong.

It's like talking horsepower and torque,
measured on a dyno, but used in the real world.
Rpm range, gearing....all factor in, and can skew results.


That 22-250 will be way more effective on varmits, coyotes, probably
even deer. Definitely if you use proper bullets for game.

Effective, as in fewer seconds to death.

Very possibly even in elk or moose if it's a lung shot.

That said, it's not a big game cartridge, and my scenario requires
too many things to be right.

Your big cast bullet will not destroy in the way a fast cartridge can,
it will do it differently. Deep long wound channels, breaking or penetrating
bone, mud whatever. Put that in the shoulder joints, hunts over.
No matter if it's antelope or bison.

For those who totally discount FPE, tell us
what we can use to measure the killing effects of missiles.

Longbow with 2 blade broadheads to 505 Gibbs with the 22-250 in between.
Give us a metric that precisely defines every stop.

Any that I'm aware of are useful, but only in Apple's to apples
comparisons. And even then, are skewed buy bullet choices, and other
factors.

Something often overlooked here is that others experiences might just
be as valid as anothers. But very due to many variables.
Big differences in hunting styles can mean big differences in guns chosen,
bullet placement/or choices of and obviously outcomes.

This is how I use foot pounds so energy- one pound lifted one foot.
If I climb a 3000 foot ridge with 4 extra pounds of fat or gear I have expended 12,000 foot pounds of needless wasted energy that day. On a 7 day hunt it is 7x that.
This expenditure is onerous in my books. Yeah , I watch my figure and carry lightweight gear . Hunting can be an endurance event.

Interesting analogy, but it’s even more complicated than that. It’s more like the energy generated inside the cylinders of the engine as related to the outcome of the quarter mile race. The results depend on so many other factors, that the energy generated inside the engine is a terrible metric to use to predict the results. The aerodynamic form of the vehicle, mass of the vehicle, the traction between the tires and the tarmac, the gearing ratio, mechanical loss, energy loss to noise and heat, etc, all play a role in how much acceleration the vehicle experiences.

Similarly, kinetic energy of the projectile at the muzzle is a terrible metric for predicting the terminal results on an animal. Some of that energy is lost to air drag, some is converted to noise and heat, some is used to displace vital tissue, some is used to deform the projectile, some is converted into vibrations in the tissue, some is used to displace fat, hair, hide, and non-vital tissue, etc. The only relatively well-correlated metric is not the kinetic energy of the projectile, but how much vital tissue is destroyed, and that largely depends on a bullet arriving with enough velocity to expand the projectile, and for it to penetrate through the vital organs.

What we need is a good 270 vs 30-06, wounding ballistics, and pressure thread....

There is no rigorous way of predicting the effects of a bullet wound. However, some basic physics can get us into the right ballpark.

Kinetic energy, momentum, and force are all intimately related. If you assume constant bullet mass, and know how velocity unfolds over time, you know all three things.

In a bullet impact, kinetic energy is not conserved. It goes to crushing and tearing tissue (permanent wound cavity) and into elastically stretching it. Cranz's Law is that wound channel volume is proportional to bullet kinetic energy, but that only sort of works, and only on slow projectiles. Kinetic energy (foot pounds) is really not a good predictor of bullet effectiveness. A single neutron at warp 9 and a 325 grain 45 caliber bullet might have the same KE, but produce very different results.

Momentum is a bit better predictor. Momentum is conserved when a bullet impacts.

On impact, the bullet sheds momentum, and the force it exerts on the tissue ahead of it is the rate at which the bullet is losing momentum. When the bullet loses enough momentum, it can no longer exert enough force to crush or tear tissue, and it comes to rest.

I think it boils down to good placement, a good bullet, and enough speed and diameter to produce a 1/2" hole 16" long.

NO!! A pox on you!

Well said, denton. Don't forget the 9 mm vs. 45 ACP debate!

Because kinetic energy is not conserved when the bullet hits the animal, and it is not a perfectly elastic collision.

More like Complexity Physics

E=mc^2 is not really applicable here, as it describes the total relativistic energy, and we're talking about classical kinetic energy.

Agreed. The only caveat is that a bullet arriving with "not enough speed" versus the same bullet arriving with "enough speed" can affect the rate of change of the mass of the bullet, which affects the impulse delivered to the tissue. Even if it isn't constant, it's not hard to integrate over bullet mass to see the effects on KE and impulse. One could then find the impact velocity that maximizes the volume or the depth of the wound channel, theoretically.

I am to lazy to deep think much about how the energy of a given load relates to killing Alaska's big game. All I am concerned about is whether my loads have "the right stuff", which is, sufficient accuracy for my shots at what ever I am hunting, shot placement, penetration and wound channel. Those are things that I can relate to easily because I can see evidence of them when I make a gut pile.

I do think energy has a role some where in determining if you have enough for the task at hand. But, I'm not ever going to figure it out.

E = m c^2 is NOT the correct formula... .c = speed of light, not just any velocity



The correct formula for KINETIC energy is

KE = 0.5 * (mass * velocity * velocity)

mass = grains / (7000 * 32.2) [7000 grains per pound; divide by 32.2 to convert mass into a weight, yes they're different]

velocity = in fps

Units work out to be [grains * lb/grains *sec^2/ft] * ft^2/sec^2
grains cancel out; sec cancel out; one ft gets cancelled .... leaving ft-lbs


Example:

140 grain bullet @ 3000 fps

KE = 0.5 * (140/(7000 * 32.2)) * (3000 * 3000) = 2795 ft-lbs of energy

E = m c^2. Can be used in either system, metric or English

Back in 1994 before we had www gun forums, we had rec.guns on usenet.

Someone pointed out that O.J. Simpson did his killing with 5 foot pounds.

I like the way you expressed - squared - on the keyboard.

For personal notes I know what MC2, means to me. But C^2 I think is easier
for others to recognize.

For myself, C = Pi X Rx2. differentiates ^2. from. X2

Thnx

Jerry

All this banter makes my head hurt....🤣🤣🤣

The Beartooth Bullets sight has all kinds of calculators.
http://www.beartoothbullets.com/rescources/index.htm

Those solutions are in line with ft.lbs of recoil energy.for each caliber(depending on rifle weight). I didn't check the formula for recoil energy before commenting,but is that a coincidence?

at age 66 its been way to long for me figure that formula out,so would someone do this and post it please.
> 100 gr. 25 caliber bullet 3800 fps < thank you,Pete53

Pete53, 3207 ft lbs for your above load.

agreed.....3,200 and change

I haven't read all of this, but I remember an article by Robert Robel where he had a formula for calculating killing power for large game animals. He called it Momentum Value and the formula is bullet weight in grains X speed in hundreds of feet per second.

His examples:
250 grain bullet at 2600 fps at the muzzle = 65 MV at 300 yards = 52 MV
130 grain bullet at 3140 fps at the muzzle = 41 MV at 300 yards = 20 MV
175 grain bullet at 2860 fps at the muzzle = 50 MV at 300 yards = 37 MV

Probably way too simple to be of any value, but easy enough to figure and make some comparisons.

thank you for those numbers,now i know how figure that. thanks Pete53

^ Probably didnt copy his buddies HW

No math equation will ever show what bullets do in tissue. Bullets kill by destroying tissue. Penetration, permanent crash cavity, temporary stretch cavity, max TC, TC length and width, neck length- all combine to offer a 3D representation of the wound channel.

The only way that correctly predicts that 3D wound channel is properly calibrated 10% ballistics gel. The FBI’s criteria matches near uniformly with mammals, whether 200lb bipedal or 600lb quadrupeds. The test consists of six events. Bare gel, heavy clothing, double wall board, 3/4” plywood, double 20ga sheet metal, auto glass. For nearly 30 years multiple projects have aimed to determine how to predict bullet performance in tissue. Every single time, regardless of who conducts the effort, the FBI’s protocol is the only one that shows correlation to live tissue.

Bare gel for light skinned animals, heavy denim for thick skinned animals, plywood for large bones in smaller 200’ish pound animals, auto glass for large heavy bones in truly large mammals.






Yes there is, see above. “Basic physics” will not, and can not tell you how deep, how wide, or what shape a bullet wound will be. Properly calibrated ballistics gel does.

They stopped Jack Belk. I wish he would show up here. Some of the smartest gunsmithing posts I have ever read on Mauser bolt welding and Sav99 design.

Kinetic energy is the better predictor here:

Hornady 40 Smith & Wesson 175 gr FlexLock @ 1010 fps: 396 ft lbs
Hornady 223 Remington 55 gr TAP URBAN @ 2983 fps: 1087 ft lbs

Hornady 40 Smith & Wesson 175 gr FlexLock @ 1010 fps: 25.3 lb-ft/s
Hornady 223 Remington 55 gr TAP URBAN @ 2983 fps: 23.4 lb-ft/s

Apparently the Campfire, as with many other questions, is going to repeat the same debate (with the same answers) that have been repeated many times over the decades in various publications.

Which of course means they're "plagiarizing" the stuff that's already appeared in the "gun rags" they claim to have quit reading decades ago--or classic books that they've apparently never read.

You practise the best method of hunting. You ignore everything that's written by anyone who claims to have knowledge of mathematics, ballistics, physics and hydraulics.

You shoot some thing with a small, hard thing that penetrates soft, vital things. The 'going in' thing makes a booboo which causes a leak. Sometimes, it's a big leak and other times, not, but you always hope for a big leak.

Well done!

P.S. It makes no difference if the small, hard thing is made of galena or pennies. It just has to make a wet enough booboo.