Since everyone is concerned with power?

[W.E.G.]

Killing an elk takes relatively little power.

Where the power issue is most important is in applying the power required to get that dead critter from the woods to the dinner table.

 

[unit91]

Here's the thing that EVERYBODY in this business gets wrong: the kinetic energy (=1/2*mass*velocity^2) is only important to the extent that the penetrator (bullet) is capable of transferring its energy to the object (or body) that is struck. Everything in this world is made up different materials, each having different material properties (i.e., your skin, Kevlar, and steel all respond differently under impact loading).

What makes tissue so unique when it is shot is hydrodynamic ram. Hydrodynamic ram is a phenomenon that occurs when an incompressible fluid (such as blood) is impacted by a projectile inside a closed container (such as skin). When this happens, the total force exerted is the sum of the mass of the projectile AND the mass of the fluid the projectile displaces, times the rate of change of the velocity of the bullet: SUM(F) = (m_bullet+m_fluid)*(dV/dt). Furthermore, approximating the conical bullet as a spherical body indicates why large caliber bullets are so lethal. The mass of the displaced fluid (blood, organs) is m_fluid = (2/3)*pi*tissue_density*radius_of_bullet^3.

As you can see, there are a LOT of computations that are strongly dependent on the bullet diameter, sectional density, etc., making "just give me a number" nearly impossible. However, remember that when a fluid-filled body (such as an elk) is struck, the kinetic energy varies with velocity^2 and bullet caliber^3. Thus, contrary to popular (uninformed) opinion, CALIBER IS MORE IMPORTANT THAN VELOCITY as a failure mechanism in living things.

Sources:
White, F. M., Fluid Mechanics, 5th Ed., McGraw-Hill, 2003.
Ball, R. E., Fundamentals of Aircraft Combat Survivability Analysis and Design, 2nd Ed., American Institute of Aeronautics and Astronautics (AIAA), 2003.

 

[Maverick223]

^Yep...particularly WRT the bold stuff.

 

[Ridgerunner665]

Unit91,
You should post more often.

 

[AzBuckfever]

WOW Unit 91...are you like a scientist or what Glad you mentioned that because what a lot of people don't know is that if you get that shot in the dead zone, the deer, elk, whatever is pretty much dead right when the bullet impacts from the displacement of everything inside, rather than the bullet penetrating whatever organs it hits. Hence the reason you shoot something in the neck, under normal circumstances it'll be dead
In reference to the hydrodynamic ram theory....you'd also have to figure in the force that an elk, deer, whatever could take before all internals would become jelly. So you're right. Too complex of a question to be answered with a simple answer But it was fun

 

[White Feather]

I personally think that most people don't care if it works, all they want is the other gun.

ALRIGHT MURDOC!! now i'm not one that gets sucked into conspiracies, but i think
you have been talking to my wife. in fact, i am sure of it!

 

[Slamfire]

Some people subscribe to a certain minimum energy requirement, such as requiring 2000 foot pounds of energy on target (not just muzzle energy). While their intent may be noble, I find this to be a foolish approach that fails to account for several important factors--bullet construction most notably

Here's the thing that EVERYBODY in this business gets wrong: the kinetic energy (=1/2*mass*velocity^2) is only important to the extent that the penetrator (bullet) is capable of transferring its energy to the object (or body) that is struck. Everything in this world is made up different materials, each having different material properties (i.e., your skin, Kevlar, and steel all respond differently under impact loading).

Momentum is conserved in collisions, not kinetic energy.

Gunwriters use KE because it is a lot easier to move a bullet 10 fps faster, and thus increase KE by 100, than it is to increase Momentum by 100. Gunwriters are paid to promote products, this is a marketing device, and the shooting community has bought into it.

I think the whole emphasis that you need to lauch a bullet from long distance is 100 percent wrong. Also the idea that powerful cartridges will kill an animal even if you don’t hit a vital spot.



This may sell powerful cartridges, but is entirely evil. Hunters are encouraged to shoot at ranges beyond a reasonable hit probability given their lack of shooting skills. Animals are being hit, run off, and die a suffering death. Hunters should be encouraged to get as close as possible and hit that vital spot and get a clean kill.

 

[Snakum]

I squirrel hunt with a 300 Win Mag. They're tough little bastidges down here.

 

[Snakum]

U91 got it. When I was trying to learn the relative value of fps of Energy vs. TKO vs. other calculations I actually pulled out my old math and physics texts. I'll take bigger every time.

(Hence a 300WM squirrel gun. )

 

[AzBuckfever]

Now I'm wondering where the heck Slamfire had to look for those pictures THOSE ARE VINTAGE.

 

[NMGonzo]

I am reading this thread with interest since I may start hunting next season.

So ... the rule of thumb still holds true?

"Hit the with the largest, fastest bullet you can get?"

 

[wyohome]

Now I'm wondering where the heck Slamfire had to look for those pictures THOSE ARE VINTAGE.

How can that 'hunter' expect to hit anything without shooting sticks?... and where the hell is his camo?

 

[wyohome]

"Hit the with the largest, fastest bullet you can get?"

Find a rifle that you shoot well and you enjoy practicing with. These guys that only fire a couple of shots to 'be sure it's still sighted in' about drive me nuts while hunting. I hate following bad hit animals, especially where grizzly bears are trying to beat you there.
I have had guys ask me to sight in their magnum rifles because they hated shooting them so much. Their theory was that they wouldn't flinch when there was an animal in the scope due to excitement.

 

[unit91]

Momentum is conserved in collisions, not kinetic energy.

Incorrect. There are three conservation laws: mass, momentum, and energy. You are correct that the kinetic form of energy is nonconservative because it is converted to other forms, but total energy is conserved. As is mass. As is momentum. I don't want to start a flame war here, but the 1st Law is absolute.

"Hit the with the largest, fastest bullet you can get?"

Not necesserily. This is an optimization problem. While it's true that larger, faster bullets have the capability to be more devastating, destruction of tissue is a goal but not the goal when hunting. You still want something left for the dinner table.

Combat may be another story entirely, but is still an optimizaiton problem. As has been discussed ad nauseum, larger bullets mean more weight, limiting the number of rounds you can carry. Faster bullets (generally) mean more pressure thus greater recoil, decreasing the number of rounds you can put downrange.

Large caliber weapons are undoubtedly devastating, but bigger may not always mean better when other factors are taken into consideration.

Find a rifle that you shoot well and you enjoy practicing with.

Amen, brother.

 

[Maverick223]

So ... the rule of thumb still holds true? [...] "Hit the with the largest, fastest bullet you can get?"

Not at all, of course you should use an appropriate cartridge for the quarry being sought (if dangerous a "stopping cartridge" would be in order), however there are a couple of factors that must be accounted for. First you need to choose a rifle that you are comfortable shooting to place shots correctly, this is paramount. Secondly, you need to weigh additional detractors of the larger cartridge such as weight, and length (in addition to recoil and fit as addressed above). Additionally you may not want a cartridge that will damage too much of the meat, though some large cartridges fair pretty well, fast cartridges typically do not. Finally you need to consider the additional cost of the firearm (if applicable) and more importantly the cost of cartridges (or handloading components). Point is the biggest, meanest, fastest cartridge is not always, or even usually the right choice for most folks.

I don't want to start a flame war here, but the 1st Law is absolute.

Not any more, there are times when mass is not conserved, but rather transformed into energy. I'm not saying that has any bearing in the current discussion (unless you have a nuclear rifle), but it isn't absolute nevertheless.

 

[unit91]

Not any more, there are times when mass is not conserved, but rather transformed into energy.

No disrespect, but I think you're misunderstanding the mass-energy equivalence theorem. The famous relation E=mc^2 implies that energy exhibits mass properties, but mass and energy are entirely separate quantities. The mass-energy equivalence is a brilliant development, but at its core is a re-statement of the 1st law. I'm not sure what your technical background is, but if you're a nerd, maybe we should jump over to the Physics forums to talk about this more. If you're not a nerd, check out the Wikipedia article on it http://en.wikipedia.org/wiki/Mass–energy_equivalence

I think we're getting WAY off topic here. The point of my original post was that the diameter of a bullet plays a significant role when impacting fluid-filled bodies. High velocities are great for reducing flight time, and penetrating structures that fail elastically (such as armor). If blood-letting is the goal, large caliber is the way to go.

 

[berettashotgun]

SO.....a bigger animal at actual hunting ranges will be within the power range of a 270/30-06/7mag with properly constructed bullets every time?
This is ground breaking.

I'd figure about 1k of foot pounds of energy will work with a good bullet.

UNIT 91~ this sounds good to me.
I will concur, a failsafe bullet is worthless at 418 yards from MY 7mm Remington mag. It only made a pass thru - .284" hole in and out.
I much prefer a "stay in the game" type bullet for my hunting, others may disagree.
I have noticed, if the bullet doesn't pass thru - I don't have to track.
One of my good friends has an uncle who swears by a 358 Winchester round with plenty of success to back up his claim.
I think my next wildcat will be a 338 or 35 caliber remington short mag.

 

[Arkansas Paul]

" Just how much power do you think it takes to kill an elk."


Not much under great conditions. Which would be fine if all elk hunting was under great conditions. It's not however.

 

[usmc1371]

I guess the answer in barney terms is it takes just enough energy to drive the projectile of choice far enough into said elk to penetrate A vital oregon causing enough damage to cause enough loss of blood to insure death.

I have killed elk with a 30-06 and now shoot a 300wm, I don't think any of the elk I have killed could tell the dif at the ranges I am willing to shoot elk. I also shot two deer with a 375 H&H last year and it worked outstanding! One head shot and one neck shot and no tracking. I have to say that a .375 cal bullet (acubond 260g) impacting the face/brain area of a deer seems to displace a lot of matter including the horns.

 

[Maverick223]

I think we're getting WAY off topic here. The point of my original post was that the diameter of a bullet plays a significant role when impacting fluid-filled bodies. High velocities are great for reducing flight time, and penetrating structures that fail elastically (such as armor). If blood-letting is the goal, large caliber is the way to go.

I agree, all I was stating is that there is a net loss of mass in a nuclear reaction, that much I know from nuclear physics. I don't know all the details because I am not a nuclear engineer, so perhaps I am missing an important detail, but I believe that mass - energy equivalence (Ε=mc²) was a modifier for the 1st law. Either way it is irrelevant to the O.P., and I completely agree with you view on caliber effectiveness.

 

[usmc1371]

^^So what you are saying is an elk won't survive a Nuclear explosion^^ Great now I need another rifle.. err launcher. The wife unit gonna be mad.

 

[Slamfire]

Now I'm wondering where the heck Slamfire had to look for those pictures THOSE ARE VINTAGE.

My collection of American Rifleman magazines.

The top picture is from the early 60's, the bottom from the 50's.

 

[Arkansas Paul]

$285 for a Mark V. Wow. That's been a couple years ago.

 

[Maverick223]

$285 for a Mark V. Wow. That's been a couple years ago.

The bottom one is for $230.00 (and up)...I'll take one of each.

 

[MCMXI]

Furthermore, approximating the conical bullet as a spherical body indicates why large caliber bullets are so lethal. The mass of the displaced fluid (blood, organs) is m_fluid = (2/3)*pi*tissue_density*radius_of_bullet^3.

Take three typical hunting cartridges/bullets ... .223 Rem (55gr), .308 Win (165gr) and .338 Win Mag (225gr) and model them as you suggest as lead balls (spherical bodies) . You define the volume of the fluid displaced as being 1/2 of the volume of the lead sphere. If we assume that the fluid has a density similar to that of water i.e. 253gr/in^3 (1g/cm^3) and that lead has a density of 2906gr/in^3 (11.5g/cm^3) we then have the following:

.223 55gr, r = 0.165", mass of fluid displaced = 2.4gr

.308 165gr, r = 0.238", mass of fluid displaced = 7.2gr

.338 225gr, r = 0.264", mass of fluid displaced = 9.8gr

So the fact that a .338 Win Mag 225gr bullet displaces 9.8gr of fluid compared to a .223 Rem 55gr bullet that displaces 2.4gr of fluid explains why the .338 Win Mag cartridge is more lethal than the .223 Remington cartridge? In all cases, the mass of the fluid displaced is only 4.4% of the mass of the bullet! Perhaps the difference in terminal performance has something to do with the fact that although both bullets at 200 yards are moving at around 2,500 fps, the .338 Win Mag 225gr bullet has 2964 ft-lb of energy compared to the .223 Rem 55gr bullet only has a measly 763 ft-lb of energy (Hornady factory ammunition).

I agree that larger bullets are generally more lethal but I'm just not convinced that it has anything to do with the mass of the fluid displaced since the mass of that fluid is negligible compared to the mass of the bullet (less than 5% of the bullet's mass). As has been mentioned, it's all about the energy of the bullet as it hits the target and the bullet's deceleration within the target which directly effects the amount of energy that is transferred to the target. A bullet's deceleration (dA/dt = IMPULSE) is greatly affected by bullet design and by what it hits ... this is obvious. More energy generally implies that the bullet can penetrate deeper into the target thereby increasing the chances of hitting a vital part of the target. Compare a .308 Win and .300 Win Mag using the same 165gr bullet. Both bullets will displace the same mass of fluid based on the model described above so they should have the same lethality right. However, common sense tells us that the .300 Win Mag with almost 700 ft-lb more energy at 200 yards will do more damage. In this case, given the same bullet, it's all about velocity.