Calculate muzzle energy

[dlbarr]

Would like to know the formula for calculating this when you know your bullet weight & speed. Looked it up online and couldn't get my mind around the explanation at wikipedia.

[jmort]

I just use on line calculators
http://www.beartoothbullets.com/rescources/index.htm

[dlbarr]

Just what I was looking for. Thanks.

[SCHUETZENBOOMER]

In easy to remember format, it's: bullet weight(in grains) x velocity squared / 450,000.

Ex: 250gr at 3000fps = 250(3000*3000) / 450000
250(9000000) / 450000
2250000000 / 450000
5000lb/ft energy

[dlbarr]

That is easy. Calculator confirms it.

Thanks! :drinks:

[MtGun44]

Not hard to calculate, but the unfortunate problem is that it
is a very unreliable predictor of field performance. I was
very enamored of this info years ago, but have found that it
generally favors small, high vel ammo, which doesn't match
well with my hunting experience beyond prairie dogs.

[DrCaveman]

Not to mention, muzzle energy dont equal target energy. Also, When a chrono is 10' from muzzle, that isnt muzzle velocity, thus does not indicate muzzle energy unless backward calculations are done.

I must admit it is fun to drop the hammer on a handgun load that is delivering 2,500 foot pounds of energy, at the muzzle. But really, a standard 30-06 load does that at muzzle, with better accuracy and range. It takes velocity to get energy, then you need bc or streamline to get point blank range.

It sounds like you get the idea. Have fun, straight shootin

[dlbarr]

... unfortunate problem is that it
is a very unreliable predictor of field performance.......


Not to mention, muzzle energy dont equal target energy. Also, When a chrono is 10' from muzzle, that isnt muzzle velocity, thus does not indicate muzzle energy unless backward calculations are done.


That is a good point. What I was trying to get [closer] to was knock-down power for hunting with various calibers & loads.

So how would I get to that data for say, a .30 cal 170gr bullet @ 1600fps out to 100 yds?

[rsrocket1]

Easiest number to remember 450,000

(mass of bullet in grains) X (muzzle velocity in fps) X (muzzle velocity in fps) / (450,000) = foot-pounds of muzzle energy

Since you usually work in grains for bullet weight and fps for muzzle velocity, the only thing you need to remember is to square that velocity before multiplying then dividing by 450,000

For your 100 yard shot, there are numerous tables and even some aps (I think Winchester made one for phones and tablets), or Bullet Drop or any number of free aps. They will calculate bullet speed at different distances so you can use the above formula to calculate bullet kinetic energy. Most require a ballistic coefficient of the bullet (BC), but the differences from one bullet to a similar design doesn't change too much.

Of course you know "knock down power" makes a ton of assumptions that often don't translate into real life, but it does allow you to compare one load to another.

[MtGun44]

Look up Taylor knockdown factor.

SWAG by an old Africa hunter. Seems as good as any, much better than ME.

[jmort]

Taylor KO is a good predictor for large/dangerous game. Beartooth Bullets has a good selection of calculators.





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Marshall's adaptation and refinement of a formula to quantitatively calculate the permanent wound channel potential of any load utilizing a bullet with a relatively flat frontal area. This calculator generates its results by utilizing the meplat diameter (in inches) of a projectile and the striking velocity of that bullet to give an outstandingly concise calculation of the true permanent wound channel left by the bullet in live targets.
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Another Beartooth Exlusive found only here! Generates the relative penetration index for any given bullet. Calculates based on bullet weight and Meplat or fronal area of the bullet. A great tool for comparing the potential penetration of one bullet to another.
>> Thornily Relative Stopping Power (http://www.beartoothbullets.com/rescources/calculators/php/thornily.htm)

Peter Thorniley designed this formula years ago. While hunting extensively both in North America and Africa he did practical field testing on numerous kinds of game animals. Living on the family orchard, he perfected this formula by continued field testing while conducting extensive depredation work. It calculates via a relative stopping power quotient the amount of gun and load necessary to cleanly take a game animal under all conditions. A great tool for comparison of one load to another, as well as the potential of one cartridge to another.
>> Taylor Knock Out Power (KO) (http://www.beartoothbullets.com/rescources/calculators/php/taylor.htm)

John (Pondoro) Taylor Knock Out Power has been respected over the years as a great comparison of two cartridges, one to another.
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Figure foot-pounds energy of a load.
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[Scharfschuetze]

The older calculations for foot pounds of energy used the constant of 450240. Sometime in the recent past that was updated to 450000 due to some arcane calculations in the scientific world.

Not that it really matters, but if you try the current formula with older ballistic charts, you'll find some minor discrepancies due to the updated constant.

Lots of ways to calculate energy, but living targets all seem to react differently and often unpredictably. Calculations are still a reasonable way to compare various calibres and bullet weights.

[dlbarr]

So what does the Taylor KO mean? For one load I got 44, another 12...

But I don't know what those actually mean. What is the range this factor deals with?

[Scharfschuetze]

Taylor Knock out Formula or TKOF.

While the classic foot pounds of energy formula measures energy by measuring the energy it takes to lift one pound by one foot, the TKO uses what may be a more practical method by measuring not only velocity and mass, but diameter as well.

The more common foot pounds of energy formula often skews energy levels in the favor of velocity. The TKOF takes into account diameter and levels the field somewhat between large diameter lower velocity rounds and small diameter high velocity rounds. Compare 22/250 and 45/70 energy levels with both formulae.

The figures generated by the various formulae are useful for comparisons as I note above. As far as the "factor" that you refer to; just establish the base line performance of your issue or favorite round and then compare other loads against that. For me, that's the 30/06 or 308 Winchester with a 165 grain bullet for big game and the 357 Magnum 158 grain bullet for handguns. The commonly used formulae only measure impact energy at a given velocity. Terminal performance and penetration of the bullet are not referenced.

Finally, compare your paper ballistics with your "hands on" or "in the field" experience. No matter what the energy level of your round, bullet placement and penetration will be more important than foot pounds of energy or KO numbers.

[SSGOldfart]

Huumm why would muzzle energy be needed? I can understand target energy but not muzzle

[dlbarr]

Huumm why would muzzle energy be needed? I can understand target energy but not muzzle
I started there because FPS data is more readily available at the muzzle as opposed to varying target distances. Wasn't considering ME as the last word on the matter, just a starting point.

If there is a specific energy formula for a certain load/caliber at X distance, I'm interested.

[jmort]

Every ballistic chart I have seen starts and at times ends with muzzle velocity.

[mnewcomb59]

T.K.O. is a garbage formula. A thrown baseball is more lethal than a 45-70 according to the formula.

Think of lethality as foot pounds and penetration. Foot pounds tells you the volume of the wound, and penetration determines the shape. 700 foot pounds applied over 12 inches is a wide wound, while 1200 foot pounds applied over 4 foot might be a narrower wound than the less powerful round.

Sure a 5.56 might have 1200 foot pounds, but it only has 12-16" penetration with the best bullets. I would rather, depending on the animal, have 800 foot pounds and 3 foot of penetration from a 357 mag.

[MtGun44]

TKO isn't for silly things like a baseball. It is a useful method of comparing
various RIFLE cartridges. What a silly and irrelevant example.

The numbers make more sense than muzzle energy numbers, when
trying to get a handle on "killing power", especially for large game and
body shots, which is what Taylor was working on.

For example: ME for a .22/250 with a 45 gr bullet at 4000 fps works out
to be 1598 ft-lbs. Muzzle Energy for a .30-06 165 gr bullet at 2900 fps
works out to be 3081 ft-lbs. .45-70 with a 405 gr boolit at 1250 fps works
out to ME of 1403 ft-lbs. Taylor knock out (TKO) numbers are 5.76 for
.22/250, 20.3 for the .30-06 and 33.1 for the .45-70.

I think that if you are shooting a moose or larger animal with these cartridges,
the actual effectiveness will be far, far more accurately predicted by the
TKO numbers than the ME numbers. Anybody think that shooting a moose
with a 45 gr .22/250 (in the body, not in the head) would work "half as well"
as a .30-06 and '15% better than" a .45-70? This is what ME comparisons get
you. TKO says that the .30-06 and .45-70 should both work well, but that
the .45-70 may be quite a bit more effective, and that the .30-06 would be around
4 times as effective as the .22/250.

Taylor wasn't trying to be super accurate, but it is clear that for the range of
normal medium to larger caliber rifles, the "figure of merit" he came up with
is a good bit more predictive of effectiveness than muzzle energy.

Bullet performance is another key issue, he usually was using solids.

No simple answers to a very complex question, but TKO is useful if you stay
within the bounds it was intended, and avoid comparing it to sports equipment.

[mnewcomb59]

If the formula had any real life validity, it would show the baseball as less lethal. Therefore, since the formula doesn't work for all projectiles, it is flawed.

Sectional density and momentum will predict penetration and foot pounds will predict wound volume. If you compared a baseball to a bullet using these metrics, you would find that a baseball has terrible sectional density and low foot pounds. Using real math that holds up no matter what projectile or what speed(sectional density, foot pounds, momentum) , we can find that the thrown baseball is not, in fact, an elephant gun.


Instead of wondering what TKO your load has, worry about energy and penetration. 2700 foot pounds is plenty enough energy for elk, but if it only penetrates 12" it is not an elk load. Likewise, a hard cast 9mm flat nose can penetrate 3 foot but most people would say it is not enough energy to make a wide enough wound.
http://www.rathcoombe.net/sci-tech/ballistics/wounding.html

EDIT: check this link, which is actually the following page of the link I posted above. Or just click "next" at the bottom of the page of the first link. http://www.rathcoombe.net/sci-tech/ballistics/methods.html

[MtGun44]

"doesn't work for all projectiles" - well, duh. Taylor never claimed it would.

Ridiculous misuse of a simple, useful comparative calculation.

Muzzle energy is far less useful because the squaring of the velocity,
while correct in the sense of the physics, does NOT correlate with
effect on target well at all. TKO is a momentum calculation with the
addition of a consideration of caliber. Nothing more, nothing less.

Carrying any of these numerical calculations to ridiculous cases is pointless.

[mnewcomb59]

https://en.wikipedia.org/wiki/Goodness_of_fit

His formula does not work with all projectiles, therefore does not fit our observed reality. This is the link I meant to send you earlier. http://www.rathcoombe.net/sci-tech/ballistics/methods.html
Look how good the observed data fits with the predicted numbers, even with extreme low velocity such as 620 fps 38 special. This is how you know you're on to something.

[dlbarr]

MtGun44,
What I appear to be slow on here is the relationship between the TKO factor & the ME #.

i.e., in your example above, the 45/70 has TKO of 33.1 which relates to ME of 1403 ft lbs.

But how does one ascertain the ME just from figuring the TKO? Is there some kind of a table with the comparative values?

[Scharfschuetze]

The same data that you need for the TKOF is the same for foot pounds of energy: velocity and mass, less the bullet diameter. A calculator will make quick work of the figures and they can be recorded in a spread sheet if so desired in order to make a table or to graph and compare the results.

In my hunting experience, the TKOF gives a more valid prediction of bullet performance than foot pounds of energy from either of the formulae or factory ballistics tables. As noted earlier, neither formulae takes into account terminal performance. Bullets for prairie dogs are a different animal than bullets for elk or bear.

Of course common sense dictates that you use the right rifle, bullet type and calibre for the job at hand. Other than for the sake of conversation, most of us have an intuitive grasp on that without the graphs, formulae or baseballs.

[mnewcomb59]

Foot pounds and penetration depth will tell you all you need to know about what the wound will be.

People worry about expanded diameter, retained weight, etc., but it is all irrelevant. Modern terminal ballistics science shows that the shape and size of the wound can be predicted by nothing more than foot pounds a impact and expanded sectional density combined with momentum.

Radically different weight and diameter projectiles will make the same wound as long they have same foot pounds and penetration depth. You could make a light 45-70 hollow point with 1300 foot pounds applied over 12 inches and you would be making the same exact wound as a 5.56. The problem is making a 5.56 penetrate 48 inches with its 1300 foot pounds (you can't).

700 foot pounds applied over 16 inches is the same wound whether from a heavy 10mm hollow point that goes to 75 cal or a 20 grains lighter 357 mag that only expands to 65 cal.



Foot pounds is volume of wound.

Penetration depth tells you the shape of the wound.

Lets explain it with balloons. I have two balloons, one is a long skinny party animal balloon, and one is a normal balloon. Your bullet has 2700 foot pounds at impact. Let's say that is equal to 3 full breaths. 2700 foot pounds is 2700 foot pounds, but your bullet tells you which balloon to pick, what shape the wound will be.

Gasp, what if I told you that coroners say a 9mm with 400 foot pounds and 16" penetration is indistinguishable from a 45 acp with the same energy and penetration? https://www.youtube.com/watch?v=aPdl_egCaCA&index=4&list=PL3F37FF69375FAD3C

The cool part about modern ballistics is that all the formulas work for all kinds of projectiles. For flat nose bullet penetration calculations you calculate sectional density as meplat and weight, not caliber and weight. Expanded meplat is used to calculate sectional density for hollow points. The formula works for baseballs too. Any projectile, even arrows fit into the modern ballistics math.

Cast boolits make the exact same wound volume as hollow points, but their diamond shaped wound is much longer and much narrower. This is called the permanent (not to be confused with temporary) stretch cavity. A flat nose bullet makes a larger-than-caliber permanent wound. The flat nose acts like a 360 degree pressure washer. You know how a pressure washer can cut you. The faster the bullet, the higher the pressure on the 360 degree pressure washer. This is why a .28 meplat at 1200 fps makes the same diameter wound as a .32 meplat at 1000. It is going faster, so it cuts further out.

Permanent stretch cavities usually only extend in to around 6 or 8 inches from hollow points (but are very wide), but flat nose non-expanding bullets can have stretch cavities extending multiple feet before the bullet slows down and icepicks. As a general rule, the permanent stretch cavity, 90% or more of the wound volume, is about 2/3 the total penetration depth (fragmenting bullets with deep penetrating cores are an exception). So if your 158 hard cast goes 3 foot, you are doing serious damage for the first 2 feet, rather than doing serious damage to the first 8 inches with a hollow point.


So, instead of TKO, think about how much penetration you need for a given animal. Can your caliber penetrate far enough for all angles? Good big game bullets penetrate 30+ inches of gel. Dangerous game bullets penetrate 4 feet or more. Then, worry about energy. Use the beartooth calculator with your meplat and velocity and make sure you have sufficient wound diameter (Stanton recommends I think .7 diameter minimum for deer), keeping in mind your bullet only make that size wound for the first 2/3 of penetration.

If you were trying to use some off the wall caliber for elephant, figure out how many foot pounds elephant stopping rifles have, and how deep their bullets penetrate. If your off the wall caliber goes deep enough and has close foot pounds, you're good to go. TKO falls apart because it places far too much emphasis on caliber and ol' Taylor had no idea how deep hard flat nose bullets would go compared to soft lead round balls . In fact, some extremely low sectional density rounds have astounding TKO. I don't see many people recommending soft foster slugs, or any kind of slugs for elephants.

[olafhardt]

The baseball theory points out the silliness of momentum
based theories. The fact that your mouth and throat absorb more energy from a cup of warm coffee than they would if you were shot with a whole clip of 30 06 cartridges shows the energy based theories also to be silly. My idea is if I shoot a whole lot of critters and they die quick then I have an effective combination.

[mnewcomb59]

To be fair, it does take a ton of energy to heat water. 2 minutes at 1200 watts in the microwave before a coffee cup boils, or 20 minutes with an open flame to boil a pot. I'm sure that kind of energy applied to a creature is deadly whether flame, microwave, or more conveniently, a bullet that punctures vitals.

Water has a very high "specific heat capacity".

[44man]

None of it works, toss the energy junk. It is what your boolit does in transition of the animal. Hit a buff with 5 tons of energy and have him stand and look at you or charge and turn you to mush would be funny. Make the bullet/boolit work. The right 30-30 bullet will work better then the wrong .300 bullet.

[goofyoldfart]

Ok, how many fairies can jitterbug on the metplat of a .357 solid vs a .357 hollow point without falling in the hollow point? most of the fairies say it is bullet placement that counts in the jitterbug contest.:lol: God Bless to all and theirs. Goofy;-).

[bhn22]

That is a good point. What I was trying to get [closer] to was knock-down power for hunting with various calibers & loads.

So how would I get to that data for say, a .30 cal 170gr bullet @ 1600fps out to 100 yds?

Nothing in the world will reliably predict a bullets effectiveness on medium to large game. The basic reason is that shot placement is more significant than any other factor, and every shot fired is different.There's and old joke about 500 FPE in the heart is more effective than 5000 FPE in...well, you can figure out the rest.

I suppose I'll get another banishment for saying this much.

[Harter66]

I have a fresh example from jus last Saturday.

A lifetime friend shoots a 300WSM. He fired 2 shots at a 160# hog head on . 1 off center head up between the eye and ear and probably parallel to the spine.the hog rolled jumped up made 2 turns and continued head on. The second shot entered head down at the cheek and went probably inside the jaw bone and between the shoulder an ribs it was killed by another shooter about 400 yds away and other than the mouth bleeding looked normal. The load was a typical 150 gr Winchester factory load suited for 300 yd mule deer . Later he shot a 340# sow quartering away shoulder to off side chest shoulder joint and it dropped full belly up. The load also halfed a 40# piglet . In the above agreements none of this is possible. The fact is the head on pig should have been dead on its feet with having had 4500 ft lbs dumped with no exits in its head and neck at 50 yds and the sow ,twice the size at 125 yd , with just 2000 ft lbs should have at best staggered and fell. The 40# piglet is the only shot that comes close to the displayed wound/energy description.

All of the numbers matter . There must be different scales applied to different shapes and construction of bullets to give them an equal set of numbers for terminal effects. I would love to see and touch the medium display where a 2800 fps barns x 150 30 cal leaves the same CID as a steel jacketed AP and a full wad cutter . Arrows don't actually leave a wound channel ,although a very fast field point might do some damage like that. There is zero chance that a 425 gr blunt from a 48# bow will kill a deer ,ok there is but that would be the most unlucky deer in North America, a field point is iffy at best ,but a 3/4 to 2" broad head is nearly a sure thing and all but absolute in the front half of the chest cavity.

We have to use whatever tools we have to make any tangible measurement we can so that we can have an applied value to put on a bullet ,load ,caliber or cartridge.

Let me show you 1 last example in Nevada by definition a 55gr 223 from a 24" bbl will make (according to the books) the 1000 ftlb /100 yd cut but a 45-75 from an 18" ported 336 with a deference 350 gr Remington factory HP falls short. The 223 is (from memory ) like 1028 while the 45-70 is 998 ftlbs. Now I wouldn't hesitate to take a Guide Gun in 45-70 elk or even moose hunting but I sure as ..... not taking a 223 even if it could be demonstrated before my eyes that both will do ,in fact the 223 should do more damage . This isn't taken to even sort of extremes ,ok sort of . Every calculation has a flaw if it isn't applied to its intended use . Taylor wanted dead elephants, Col Bell delivered dead elephants and I know 50 people that are dumbfounded when I say "the 45-110 matches numbers bullet for bullet with the 458 WM , it just takes 12" more bbl . Check out the Lyman 48th and look at the 405 gr bullets" . I don't know 1 person that would even consider a 223 for elk nor walk away from a 45-70 . I do know several that would shun a 7x57 for deer no matter how many elephants it killed.

[BAGTIC]

There is no such thing as 'knockdown power'. Lethality is caused by damaging vital organs and tissue. Among soft targets such as animals momentum density determines depth of penetration . Using high expansive/frangible bullet KE determines the volume of the wound. Where the penetration or cavity occurs determines lethality.

[stephen m weiss]

Bagtic has that right. And what we want is to do the minimum damage to the animal while making it not get away. And of course we want it reliably done.

I started trying to work on a terminal ballistics calculator by inverting my exterior ballistics calculator, but it doesnt work well. Specifically, it does not predict the bullet stopping well at all. I think as the velocity gets low, around 100 fps, fluid drag loses importance relative to coulomb friction behavior. But, whats the coefficient of friction of a bullet rubbing through muscle, lung, or bone?

I did some estimations on death time for a deer whose jugular vein is shot out. I came up about 10 minutes because their head is so small compared to their body, there is just not much blood going to the head. On the other hand, I don't know what fraction of blood loss causes loss of conciousness. That should depend on the volume elasticity of the blood chanels. I have no data on that either.

hmmm...

smw

[303Guy]

Energy does the damage while momentum does the penetration. Actually, energy can be quite meaningless. It's power that matters. Power is the rate of energy transfer.

I've witnessed a 22 hornet versus a 308 on turkey and on goat. The hornet was loaded hot with 55gr bullets at about the same muzzle velocity. At 200m (220yds) the effects of the two bullets were indistinguishable. Similarly on goats. The hornet and the 308 performed the same (shorter distance). That similarity would of course disappear on larger animals. Different bullets would change things too. So would shot angles. But for the bullets in question, the rate of energy transfer (power) was about the same. Neither represents the maximum 'power' potential of the projectiles.

Have a look at the Thornily Stopping Power calculator. Looks interesting.

http://www.beartoothbullets.com/rescources/calculators/php/thornily.htm

It also gives a convenient game requirement comparison (which I'm sure doesn't take into account all aspects of bullet design and shot placement).


TKO is a momentum calculation with the
addition of a consideration of caliber. Nothing more, nothing less.MtGun44 is quite right in what he is saying. The TKO is better than energy alone. Perhaps a combination of caliber, momentum and energy would be more encompassing (that would eliminate the thrown baseball) and would take into account the effects of impact velocity.

[olafhardt]

I got this theory, worth exactly what you are paying for it. I think at least some of the time an animal is stunned by the impact and bleeds out before it recovers from shock.

[mnewcomb59]

[QUOTE=303Guy;3246170]Energy does the damage while momentum does the penetration. Actually, energy can be quite meaningless. It's power that matters. Power is the rate of energy transfer.

Energy and penetration , with penetration being the most important . Foot pounds tells you volume of wound, but you still need to know penetration depth to understand what the wound will look like. 44man said that sometimes his 300 grainers don't do good damage to deer and this is because that bullet will penetrate 5 feet of ballistics gel and he is only using 1/3 to 1/2 of his damage potential. A 200 grain will exit deer on Texas heart shots, and will only exit piss hard having used most of is energy. A 200 grain is enough bullet for any shot angle on deer, and any more than that is just putting a bigger hole in the dirt behind he deer.