How much energy in ft lbs ?

ft lbs of energy dont kill animals bullets do.

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This was true in 1780...

The old stand by of the gun writers in magazines like Sports Afield and Outdoor Life back in the day was 1000 ft lbs on target. THAT, however, I find a little high for guns that DO kill more with the bullet than energy, stuff like .50 caliber 385 grain minie balls from a muzzle loader. Even in handguns, guns that depend more on bullet trauma than energy for a clean kill, stuff like the .44 mag can get down in the 600 ft lb range (this is JMHO, nothing to back it up, but experience) and still do the job.

All that said, 1000 ft lbs is a good general rule of thumb for whitetail deer IMHO. I have no quarrel with it, anyway.

however, I find a little high for guns that DO kill more with the bullet than energy, stuff like .50 caliber 385 grain minie balls from a muzzle loader. Even in handguns, guns that depend more on bullet trauma than energy for a clean kill, stuff like the .44 mag can get down in the 600 ft lb range (this is JMHO, nothing to back it up, but experience) and still do the job.

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I wonder if it could be said that the importance of kinetic energy is inversely proportional to projectile mass and diameter.

Further, what sort of experiment could be designed to test the above hypothesis?

JohnKSa said:

Bullet trauma is a function of kinetic energy.

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But there are differences in the efficiency and speed of the energy transfer from the bullet to the intended target. Two bullets with the same kinetic energy won't necessarily perform in the same manner. Bullet design is critical to the efficiency and speed of the energy transfer.

jmr40 said:

Conventional wisdom is 1000 ft lbs for deer, or black bear, 1500 for elk, moose or large bear, but those numbers are not written in stone. What you want is enough penetration to get the job done, and different weapons, bullets accomplish this in diffeent ways.

The above figures are fairly accurate with most rifles, and bullets, but some rounds, shooting heavy, slow bullets such as muzzle loading rifles, shotgun slugs, 45-70, 44 mag etc will still give you plenty of penetration with much lower energy numbers. Same with arrows shot from bows.

Bullet construction also comes into play. Some of the newer solid copper bullets give more penetration than conventional bullets at the same energy levels.

With modern hunting rounds, 30-06, 270 etc. I've about concuded that impact velocity is probaly a better predictor than energy numbers. Most bullet manufacturers list recommended a maximum and minimum impact velocity. If the bullet impacts game too fast it will blow up and not penetrate enough. Too slow and it will not expand and will cause too little damage. With most rounds the minimum impact speeds are around 1600-2000 fps depending on the exact bullet. Look at a ballistics chart and find the range where your chosen bullet drops below around 1800 fps and that is probably the max effective range for that bullet.

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Please. Show me a shotgun slug that delivers less than 1000 ft pounds. Most slugs are pushing 2500 ft pounds at the muzzle. Even your reduced recoil slugs are 1400 foot pounds.

Bullet design matters alot. A light, pointy bullet like 223/556 may penetrate deeply on flesh, but struggle with bone, where a heavier blunt bullet like 30-30 would perform much better. I think mass matters quite a bit. Most of your hunting calibers are trucking along at relatively the same speed +/- 20%. But if you've got one bullet weighing twice as much as another...

It's simple high school physics. Greater momentum gives you greater penetration. Mass*velocity. That's why birdshot is worthless where buckshot excels.

Velocity and mass, the two components of kinetic energy, describe how much movement in a given time, and how much is moving. The effect of mass on kinetic energy is seen as INERTIA, the bullet's RESITANCE TO CHANGE IN VELOCITY in any given medium. assuming equal inintial KE, a heavier bullet at lower speed will be harder to stop than a lighter bullet at higher speeds. if you drive both a large truck and a small car, you'll notice the same effect on braking distance. This is why large, heavy bullets kill reliably - deep penetration, even if they lack the high KE to deliver instantly debilitating shock/ trauma. they may also be percieved as more reliable because at lower velocities, weight retention/ bullet fragmentation are less likely to be problems.
it's an old argument that won't be solved to anyone's satisfaction in this thread.
Remember, if i looks stupid, but it works, it ain't stupid.
AND
bullets work best when you put 'em where you're 'sposed to.

don't really know what this has to do with what you are talking about but when i was 10 or 11 and out squirrel hunting i shot a 6 point buck at about 50 yards with my 22 lr and the bullet went clean through and was lodged in the skin on the other side. It took out both lungs and he fell after about 3 steps. I would never do anything like that now i was just a kid that didn't know any better but I still think about that and it really surprised me at the penetration and very cean kill i got with that .22

mass plays an equally important part since it's directly related to both quantities.

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It is directly related to each, but not equally important. Since energy is related to the square of velocity, velocity is primarily important in energy calculations, with mass of secondary importance; in momentum, the mass and velocity are both of primary importance.

As you know, that's one reason that those favoring momentum favor slower, heavy bullets, and those favoring energy favor lighter, faster bullets.

I think the point is being made that by specifying energy figures, one lets in light, fast cartridges like .223. Still, as the 1000 ft-lb figure doesn't rule out "good-ol'" deer cartridges like the .30-30, it's not a big deal.

For comparison, we can look at some African countries. Namibia specifies about 1000 ft-lb for game up to springbok (think yearling deer), about 2000 for animals up to eland (1500+ lb antelope), and about 4000 for Cape buffalo.

I have bowkilled a couple dozen deer (no kidding) and got a complete pass thru on most (~20) of them.
As long as I did not hit spine, or use a large mechanical, I expected a pass through.
How much energy was needed for this kind of penetration? 60# KE.
For the non-archers that number would represent a 400 gr. arrow going 260 fps topped with a sharp broadhead.

I'll be taking my boys hunting this fall with a .223 (it's legal)
One bullet option: 60 gr. Nosler Partition handload @ 2,807 fps (yes, I have a chrono) out of a 16'' AR
The Nosler handload produces 1,050# KE at the muzzle and will have very close to 1,000 remaining when (if) it impacts a broadside, standing still, deer nearly 30 yards away.
My boys will be restricted to "extended" bow range for their .223 hunting; they will shoot from a tripod rest inside a ground blind.
I've tested the Partition in water filled gallon jugs and it made a small hole on the back of the 4th jug, expanding to .40 - .41

It's not how much energy you have, it's where it hits, how big it is (or gets)and how much it can penetrate that counts.
A .223 through the lungs will have a much better result than a 30/06 in the guts.
Using "more" gun doesn't increase the heart & lung area on a deer.

Nah. Like you said, all in how you look at it.

Look at two .308 loads: a 110 gr bullet at 3165 fps has 2446 ft-lb of energy and 1.54 lb-sec of momentum. A 178 gr bullet at 2775 has 3043 in energy and 2.19 of momentum.

Increase the bullet weight 62%, and you get a 24% energy increase, but a 42% momentum increase.

Or go to the .45-70 for comparison. A 350 gr bullet @ 2050 has about the same energy as the .308 178gr at 3032...but 45% more momentum at 3.17 lb-sec.

You can play around with other cartridges, too; you will consistently find that an increase in bullet mass results in more gain in momentum than in energy, since for any given cartridge, in order to increase bullet weight, you'll have to sacrifice velocity (if you stay at the same chamber pressure).

Mass (in rifle ballistics) has more importance to momentum than to energy, even if it "plays an equal part in both calculations."

Bullet design matters a lot in high velocity, small bore rifles. In a 50 caliber, I cast my own Minie balls. They plod along at 1400 fps from the muzzle and will kill BIG game, bigger than deer, past 100 yards. They're big, flat, don't need to expand, and punch a nice 50 caliber hole though and through. Blood loss is the primary method of killing with a bullet like that, sort of limited on energy, or at least energy transfer, but just as effective within their range of rainbow trajectory as your .30-06. Don't mistake, though, a 385 grain bullet at 1400 fps is still packin' 1685 ft lbs, quite a bit less at 100 yards, but still, has some good energy. The killing power of the bullet, though, seems way out of proportion to its energy level, which is understandable when you look at the size of the bullet.

I'm kinda into the front loaders now days for hunting. I shot my first deer with my CVA Wolf this season and he was DRT, just as dead just as fast as if I'd hit him with my 7 mag. And, as they say, you can eat right up to the hole, very little meat loss. That's not the reason I'm into it, though, just got this sulfur running in my blood. I've been shooting BP for a long time, but the Wolf is the first rifle I've owned that I don't have to shoot to unload, makes it more convenient if I don't see anything.

I don't find there's a lack of good bullets for my high velocity rifles. I shoot a Sierra 150 in the big 7, alternately a Nosler Partition 160 grain. I shoot a Nolser BT 150 grain in the .308 and a Sierra 100 grain Game King in the .257 Roberts. All work well on deer and hogs and the 160 grain 7 is a good getter of bigger game. Where finding a suitable bullet for deer gets dicey is when you get small, 22 caliber, .223 particularly. Now days, there are controlled expansion bullets available and .22-250 has been quite popular for the recoil shy and new shooters in Texas for a long time, but I'm still a believer is more power for deer hunting. The AR craze is all the rage now days, but I find my hunting rifles still work best for me. I don't consider anything smaller than 6mm bore for medium game, personally. If you wanna hunt deer with your AR, knock yourself out. Limit your range to 100-150 yards due to the limited energies and even more limited bullet size and use a premium bullet. Trying to use military surplus from a .22 is just cruelty to animals.

A .30-30 will do it.. and they have what 1300 ft lbs.. I can't think of many legal firearms in VA (.23 or larger caliber) that wont do it.. the subsonic stuff is about it.

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A good .30-30 load leaves the muzzle at around 1800 ft lbs. I load a 150 Nolser BT in .30-30 and shoot it from a 12" pistol and it kills deer quite cleanly. On target energy at 200 yards is right at 1000 ft lbs, great BC with that boat tail bullet. I've run the numbers. It starts out shy of 1400 ft lbs at the muzzle, but the high BC helps save that energy on out there. It's flat shooting for a pistol, too, 3" high at 100, spot on at 200, and will out shoot a lot of rifles. That load is 1.5 MOA in the gun topped with a 2x optic. My fartherest kill with it was 90 yards, but I have confidence in the gun to 200 if I do my part.

but that's not the same thing as saying that mass does not play an equal part in the two calculations. Clearly it does.

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It's also not the same thing as saying what you originally said, which was this:

Whether you lean towards momentum or energy as a rough relative predictor of terminal effect, mass plays an equally important part since it's directly related to both quantities.

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So, as I said: no. If you "lean towards" bullet momentum to get hunting effectiveness, you'll likely favor a heavy bullet. But if instead you require (as these regs do) a given level of energy, a lighter bullet allows you to get that with less recoil than a heavier one; and so a lighter bullet is often chosen.

Or, to put it another way: bullet mass is more important to achieving glerb than blivet. If that clears things up.

OK terminal ballistics is my speciality to let me break this down, first let me make this abundantly clear there is no real value of ft lbs of energy that equals a clean kill....why? Because there are too many other factors involved. There is a general rule that 800 ft lbs is the minimum for deer but many hunters with their 45 colts/44 mags that have proven that this is not a hard and fast law of psychics many many times. Heavier projectiles and higher SD projectiles can wound more efficiently, I have proven this point over and over again, lighter, faster, lower SD projectiles tend to deposit more of their energy shallower in the wound canal and slower heavier projectiles tend to cause more damage deeper in the wound tract (through the vitals), read my thread "the complex science of terminal ballistics" if you want a more in depth information on this. http://www.thehighroad.org/showthread.php?t=646058&highlight=complex+science+of+terminal+ballistics
I have a nice ballistics gel comparison there of a bonded 223 and 44 magnum which illustrates exactly what I am talking about. The 223 has more energy and makes a bigger mess of the first few inches, but the wound deeper in is no comparison the 44 which has less energy simply blew it away.

Hog hunting

Adelbridge, you hunted hogs with a knife???



You are...The Man!

JohnKSa said:

"Whether you lean towards momentum or energy as a rough relative predictor of terminal effect, mass plays an equal part in both calculations since it is directly related to both quantities.

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Mass, energy and momentum are not DIRECTLY related. Take my comparison of a 223 rem to a 44 magnum. The 223 pushing a 55gr bullet to 3100fps has 1173ft lbs energy and 24 lbs of momentum, the 44 magnum 240gr at 1400fps has 1044 ft lbs of energy and 48 lbs of momentum, less energy yet twice the momentum there is nothing direct about that relationship. Mass has much more effect on the momentum figure and speed has much more to do with the energy figure although this also means they are all related just not in a direct linear fashion.

So in spite of the fact that my position and meaning are entirely clear

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As were mine.

What's amusing is that in the process of objecting to my (perhaps sloppy but entirely conventional) use of the word "important" you've invented/made up...

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I've made up nothing.

We were talking about rifle energy requirements (remember? I reference the thread title, OP and subforum title). In that context, yes (without me "making up" anything) bullet mass is less important than it would be if the OP had specified momentum.

That you decided to take us down a physics equation rabbit hole--to make what point about needed energy, again?--is, as you say, "amusing." Trust me: if you had posted your comments on a "Physics: Momentum and Energy" website, I would have made no comment.

Context.

And yes, now that we've both found something "amusing", your "pot and kettle" comment finally applies.

Kachok said:

Mass, energy and momentum are not DIRECTLY related. Take my comparison of a 223 rem to a 44 magnum. The 223 pushing a 55gr bullet to 3100fps has 1173ft lbs energy and 24 lbs of momentum, the 44 magnum 240gr at 1400fps has 1044 ft lbs of energy and 48 lbs of momentum.

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I always calculated momentum as: projectile weight x projectile speed / 225,120 = momentum

55 gr. x 3100 / 225,120 = .76 momentum

In my previous example involving arrows, I cited a 400 gr. arrow @ 260 FPS which has 60# KE

400 gr. x 260 fps / 225,120 = .46 momentum

Using my calculation, a 95 gr. bullet @ 875 fps (pocket 380) produces a momentum of .37

A snub 38 special shooting a 130 gr. bullet @ 850 fps = .49 momentum

I think subscribing to some arbitrary energy figure as an indicator of effectiveness or range to be foolish. Energy is an overrated indicator of performance in general.

In theory, energy gives you a neat little number that describes the amount of work a projectile is capable of doing. In practice, how the bullet does its work is far more important than how much work it is theoritically capable of performing.

For the purposes of determining effective range on game, velocity is actually a much better indicator. Within reason, if you're using something between .243 and .30 caliber, and you're using a bullet designed for medium game, the ammo manufactures have done the hard work for you. They've already designed the bullet to expand reliably at most operational velocities the bullet will encounter, and to retain enough mass to achieve adequate penetration. Most modern projectiles are designed to perform well within a pretty wide range of acceptable velocities. However, as a bullet loses velocity going downrange, it will eventually reach the lower velocity threshold it was designed to expand at. For most modern bullets, this threshold is somewhere around 1800 to 2000 fps. Below this velocity, most bullets will expand very little, if at all, and will therefore be a poor performer on game regardless of how much remaining energy it has, and despite the fact that it may still be able to penetrate enough to be lethal. Therefore, I recommend you consult the manufacture of the bullet you prefer and ask them what velocity window you're looking at for reliable performance in game, specifically, the lower velocity threshold. Some manufactures, namely Hornady, also publish this information in their loading manuals. You then need to determine as accurately as possible the velocity you are achieving from your cartridge/rifle with that projectile, and the atmospheric conditions you'll be hunting at. Plugging these numbers into an external ballistics program should then give you a pretty accurate indicator of how far downrange that bullet should be before it runs low enough on steam to quit reliably expanding.

Keep in mind, this number is probably going to be lower than you'd like--most cartridge/bullet combos are going to cross their respective lower velocity thresholds somewhere around 400 yards. This is a decent shot on a game animal, but still well within the capabilities of a practiced rifleman with a decent rifle and optics. To extend your range, about all you can do is load a softer bullet at the expense of penetration at higher velocities (closer ranges).

CDW4ME said:

I always calculated momentum as: projectile weight x projectile speed / 225,120 = momentum

55 gr. x 3100 / 225,120 = .76 momentum

In my previous example involving arrows, I cited a 400 gr. arrow @ 260 FPS which has 60# KE

400 gr. x 260 fps / 225,120 = .46 momentum

Using my calculation, a 95 gr. bullet @ 875 fps (pocket 380) produces a momentum of .37

A snub 38 special shooting a 130 gr. bullet @ 850 fps = .49 momentum

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Momentum can be expressed in any measure of weight any speed, the SI unit of Momentum is kilogram meters per second (kg*m)/s I used pounds because it was late and I cheated and used an standard momentum calculator. Mass and momentum are directly related as the formula always starts with Mass x Velocity no matter which measures you use for each, but mass and energy are not directly related since doubling the speed results in four times the energy or EK = (1/2)mv2. That is how high speed projectiles can have more energy yet less momentum. Doubling speed also increases drag passing through a body by four fold, that is the reason very high speed bullets tend to "dump" much of their energy very shallow in the wound canal and an old slow and heavy 45-70 can blast through a cape buffalo despite it's lackluster energy figures.

Kachok said:

Take my comparison of a 223 rem to a 44 magnum. The 223 pushing a 55gr bullet to 3100fps has 1173ft lbs energy and 24 lbs of momentum

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You've discounted the effect of gravity for the ft-lbs calculation (energy) so why not do the same for the momentum calculation? The momentum is 0.76 (lbm-ft)/sec.