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!

[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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[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/b.../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/b...s/methods.html