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Mgt3
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Is kinetic energy or momentum a better indicator of bullet penetration?
Mgt3 said:The reason I ask is because of confusion over various dangerous game hunting articles. In one magazine I read not too long ago, the authour discussed hunting elephant in Africa and stated that, to penetrate the elephant, 4,000 pounds of energy is needed and a minimum rifle such as .375 H&H or .416 Rigby. Another article discussed the ability of a .500 Smith and Wesson magnum or a .454 Casull, both which have between 1,500 and 2,800 lb. ft. of energy, to hunt the same kind of dangerous game (elephant, cape buffalo) effectively. How is this possible?
maverick_starstrider said:Well firstly neither pounds nor lb. ft. are even a unit of energy. In empirical the units of energy would be lb. ft^2 / s^2. So I woudn't think the physics analysis of whatever you're reading is worth the glossy paper it is written on. Secondly, there are a lot of factors that effect the effectiveness of a bullet other then their muzzle velocity (shape for one).
timmay said:1. Ft-lbf is a perfectly acceptable unit of energy in the ballistics world. Bear in mind that's pounds force times feet.
2. Let's extrapolate what you need from ballistic standards testing. For standardised vest tests, you find the ballistic limit by finding the bullet velocity at which 50% of the shots will cause penetration. This is found for a specific bullet, meaning it's a combination of mass (hence energy) and geometry (difference between shooting with a spitzer or a ball end round). You could probably penetrate an elephant's skin at the lower bound of the energy ranges stated with a spitzer, but a higher energy for a ball end with the same mass.
Not knowing much about the specific rounds you've mentioned, what's the difference in ogive/ends?
Mgt3 said:Is kinetic energy or momentum a better indicator of bullet penetration?
raknath said:Kinetic energy is converted into momentum as the bullet leaves the gun.
The Kinetic energy of the bullet leaving the gun is actually resolved into two components
The forward momentum of the low mass bullet and the reaction force of the gun which is the feedback you get.
Now Kinetic energy is defined by the mixture of gunpowder that's present in the gun, but the momentum is defined by the mass of the bullet, like let's say there is some leakage of gun powder at the time of firing the bullet would actually not travel the distance and be less effective.
Ideally all bullets are designed for penetration . So you possibly need to say what kind of penetration u need
Essentially what you are asking is like is the weight of the hammer or the speed of the blow determining the cracking of the nut. They are quite the same products
xxChrisxx said:Not to be overly blunt or anything, but that's utter crap. KE and momentum are NEVER 'converted to one another' and they are fundamentally different things.
KE = 0.5MV^2
P = MV
Both KE and momentum are defined by velocity and mass.
Right but isn't it because of the weight that the impact actually cracks the nut?xxChrisxx said:The penetration could be described by either (but is best described by using both), however it needs more detailed description than just a number. The nature of the impact is the important key to both penetration and damage.
Although you have the hammer analogy kind of correct, the thing that actually cracks the nut is force, not momentum or kinetic energy. As force is the mass times acceleration (which is most conveniently found by differentiating mommentum over impact time).
The reason why large slegehammers are used is because, there is generally a maximum swing speed for a hammer and its very difficult to increase it. Yet its very easy to increase mass.
Mgt3 said:There is a great difference in power between these two cartrdiges, yet both seem to work on elephant. Can a mathematical equation be derived that can show the approximate penetration of a bullet given power and shape?
xxChrisxx said:Back the the bullet: To get a true description of the penetration power, both KE and momentum should be used. Along with the geometry of the bullet and the impact.
Danger said:...the .475 H&H Magnum rifle. It produced 10,000 ft/lbs of muzzle energy...
Danger said:Damn... I still can't edit.
What I was going to add to my last post is a quote from my 'Cartridges of the World' entry about the .475.
'There is absolutely no need for a cartridge of this power to hunt anything on this planet.'
turbo-1 said:I've got a 50-round box of custom .45-70 hand-loads given to me by a couple that loads for BIG handguns. Some each of 405 and 500 gr solid round nose that tach out at over 1800 fps. Now, I need to get lucky enough to win a moose permit in the yearly lottery. Leona LOVES Tom Selleck, and I helped Bill get her a lever-action Winchester that had belonged to him. Bill knew that I hunted with a single-shot Ruger Model 1, and they surprised me with the hot loads as a thank-you. I have put very strong warnings on the plastic box - those loads would blow up a Marlin or Winchester .45-70 and possibly kill the person pulling the trigger.
Nope, and if I did, I certainly wouldn't want to run those hot loads through it. Ouch! My Model 1 can pummel my shoulder with standard 405 gr .45-70 loads if I put enough rounds through it. It's an accurate rifle for target-shooting, though. My first two rounds ever made an elongated hole in the center of the target at 75 yards, using the open sights. My father was looking through my binoculars and said that I missed the paper. I knew that was not the case, so we had to walk up and verify.Mgt3 said:You got a Magnum Research BFR?
vociferous said:I am not certain if it has been discussed here, but the material being penetrated and the density and shape of the bullet are often crucial. For instance, I strongly suspect that a 12 gauge shotgun slug has more kinetic energy than a 5.56 fired by an M-16 or a 7.62 fired by an AK-47; however, both those bullets can penetrate body armor that a shotgun slug cannot.
Mgt3 said:I think that has to do with the bullet being made with a steel core. There are steel core shotgun bullets that will penetrate body armour.
Mgt3 said:Is kinetic energy or momentum a better indicator of bullet penetration?
praveen kumar said:I think that it is neither kinetic energy nor momentum is a better indicator for bullet penetration but the design of bullet.
Mgt3 said:A .45 ACP would have no chance at deeply penetrating something - or would it?
Mgt3 said:What is the rational basis behind laws that require hunters to use a large caliber rifle on dangerous game in Africa, if you know?
Lok said:Hunting is a bloody sport for the weak of mind.
Mgt3 said:I suppose you don't eat meat?
Lok said:The sport is unfair and as above.
I always enjoy watching or hearing of some hunter being killed, maimed, torn apart etc.
negitron said:You are ignorant.
Kinetic energy is the energy an object possesses due to its motion, while momentum is the measure of an object's motion based on its mass and velocity.
Both kinetic energy and momentum play a role in determining the penetration of a bullet. Kinetic energy helps to overcome the resistance of the target material, while momentum helps to push the bullet through the target.
Both kinetic energy and momentum are important for bullet penetration, but the importance of each may vary depending on the target material and the type of bullet being used. In general, a higher kinetic energy or momentum will result in deeper penetration.
The kinetic energy of a bullet can be calculated using the formula KE = 1/2mv^2, where m is the mass of the bullet and v is its velocity. The momentum can be calculated using the formula p = mv, where m is the mass and v is the velocity.
The kinetic energy and momentum of a bullet can be affected by various factors such as the mass and velocity of the bullet, the type and shape of the bullet, the density and composition of the target material, and any external forces acting on the bullet.