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Originally Posted by vapodog
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.

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

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Originally Posted by denton
What we need is a good 270 vs 30-06, wounding ballistics, and pressure thread.... smile

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.


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.

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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.

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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




Last edited by CJC73; 02/28/20.
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Originally Posted by vapodog
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.



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

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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.


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Originally Posted by CJC73



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


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


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


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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?

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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


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Pete53, 3207 ft lbs for your above load.


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Originally Posted by pete53
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
agreed.....3,200 and change

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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.


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

Last edited by pete53; 03/01/20.

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Originally Posted by Infidel

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,


^ Probably didnt copy his buddies HW

Last edited by Crockettnj; 03/01/20.

Originally Posted by Archerhunter

Quit giving in inch by inch then looking back to lament the mile behind ya and wonder how to preserve those few feet left in front of ya. They'll never stop until they're stopped. That's a fact.
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Originally Posted by Dillonbuck


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




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.



Originally Posted by denton

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




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.

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


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Originally Posted by denton
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.


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

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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.


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