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> Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?
Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?
@ 07:20 pm (GMT) |
DR015I recently opened a discussion about why some cartridges that have low energy but more weight and size are usually recommended for killing larger targets while cartridges with more energy but less size and weight have a more comprehensive recommendation, including targets and smaller size and weight. I used as an example the classic 45-70 in comparison to the 7mm RemMag and the 30-06 Springfield, where the 45-70 has low energy, especially above 100 meters in relation to the other 2 cartridges mentioned that have double or almost that.The responses I got were unanimous in saying that the 45-70 is more recommended for larger targets, as it has more "momentum" to the detriment of the other two mentioned. When studying this superficially, I realized that the "Moment" has a greater capacity for penetration, as it is a directed force, while kinetic energy has a greater capacity for "destruction" as it is an undirected force (inelastic). And that brought me here, I want opinions on this subject in relation to the lethality of a cartridge. After all, what determines the lethality of a cartridge: Momentum or Kinetic Energy? The more you support your opinion, the better it will be understood by me. After all, I am a ballistics enthusiast, with little knowledge but a lot of desire to increase and improve it. |
Replies
@ 07:33 am (GMT) |
Nathan FosterRe: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?Hi DR015, I have been writing about this for some time now, to be published in an upcoming book. The subject cannot really be covered in a short forum reply.The question is whether momentum or kinetic energy has the greatest effect on terminal performance. The answer is neither. Without taking the bullet shape and construction into account, any such model is simply theory. These days, people are using theory to prove scientific concepts without taking facts or evidence into consideration. Science has become an ideology, bordering on a new religion. The best way to determine the lethality of a cartridge is to test it on game. There is simply no substitute for this. An example of the effects of bullet shape can be found in my article, The effect of the meplat on terminal performance. https://www.ballisticstudies.com/Knowledgebase/The+Effects+Of+The+Meplat+On+Terminal+Ballistics.html Examples of the effects of bullet construction can be found throughout the knowledge base. Otherwise, you have already identified basic factors such as momentum being key to penetration on large bodied animals. See also: https://www.norma-ammunition.com/en-us/norma-academy/dedicated-hunting/ammunition/effective-game-killing The best way to summarize this is to quote past Hornady Ballistician Dave Emary. He has distilled this into one single accurate statement - "it depends". |
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@ 01:42 am (GMT) |
DR 015Re: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?I read your article and managed to understand a good part of what was said, the small part that I couldn't understand was due to a lack of personal knowledge on the subject, although there is a lot of enthusiasm on my part to increase and deepen my knowledge about this area of physics (as initially stated).Just to give some “light”, even if superficial, on the subject in relation to the penetration capacity of a cartridge: As you said in your article, and also reaffirmed here, the lethality of a cartridge goes beyond its energy and momentum, which includes the “projectile type” factor. In this sense, is it possible for a cartridge with greater energy but less impulse to be more penetrating than a cartridge with opposite characteristics, given that the projectile has properties that seek this effect? |
@ 07:22 am (GMT) |
Scott StruifRe: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?Having had mixed success with various cartridges and bullets, as well as studying Nathan’s work for several years, I have concluded that attempting to develop a formula based on buzzwords such as momentum, sectional density, kinetic energy, and so on, is a fool’s errand.There are 3 reasons such physical properties are next to useless in predicting terminal performance 1. Manufacturers of hunting bullets design them to perform consistent with customer expectations regarding external ballistics and terminal ballistics, neither of which is necessarily consistent with quick dispatch of game. 2. Manufacturers design hunting bullets to perform optimally (i.e., consistent with customer expectations) when shot placement is ideal, a criterion also dictated by customer expectation. 3. Shot placement on game is often not ideal. Even within a line of hunting bullets, those of various calibers and weights may differ in construction, according to the manufacturer’s perceived view of customer expectation. Jacket thickness is an example. Manufacturers will vary it according to their best guess of what a customer expects from the bullet. “The deadliest mushroom in the woods,” is a prime example. Remington knew what their customer wanted: A shank with a mushroom lodged against off-side skin. Momentum, sectional density, and kinetic energy have nothing to do with it. The forums are replete with ad nauseum debates about the efficacy of certain bullets, the merits of pass-through, wasting energy on the hillside behind the game, blood trails, etc., all driven by customer expectation. A bad shot strikes a spine, the bullet is declared an engineering marvel. The only apples to apples comparison possible is to compare match bullets of the same line but in different weights and calibers. Match bullets are constructed with the thinnest possible jackets, in order to ensure stringent manufacturing tolerances, and thus accuracy. This is the only place where momentum, section density, and kinetic energy mean anything with regard to terminal performance. |
@ 11:51 am (GMT) |
Magnus VassbotnRe: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?Hi.In my experience, as long as you have enough penetration from whatever angle you shoot, high energy/ high velocity gives quicker and more dramatic kills than high momentum/ hi mass. Whether that penetration comes from bullet construction or high SD is sort of another discussion. But a slower, heavier bullet will for the most part make the animal just as dead, but not as quickly. Very generally speaking, with all the usal caveats. In practical terms - on medium sized abimals like red deer, pigs and most planes game, penetration/ momentum is rarely an issue with normal cartridges with normal bullets. Whatever that is... Magnus |
@ 01:11 am (GMT) |
Daniel SchindlerRe: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?Like DR...I put in the time to uncover Truths. And there's a LOT of information out here in Google land. Speaking for myself, it can be a bit frustrating when trying to separate facts from opinions and speculations on external and terminal ballistics.I found this particular thread refreshing. A ray of light on common sense. Truths. While I'm certainly not new to all this, I bow respectfully to the many here who are far more learned than I am on ballistic matters. I'm confident DR shares my appreciation for the responses you gentlemen posted to his good question. Learning? Mission accomplished. Thank you. Cheers. |
@ 12:06 pm (GMT) |
euanRe: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?Hello, I don't post much, but I teach the physics of this sort of thing and it's interesting to me.From a physicist's perspective, momentum and energy are things a moving object has. They belong to the moving object. Force is the 'push' applied to the target. So the projectile has momentum and energy. The projectile will apply a force to the deer. A 150grain projectile from a .308 has around 7 kg m/s of momentum. A charging All-Black has about 1200 kg m/s of momentum. So momentum would appear not to predict lethality. A 150grain projectile from a .308 has around 3000 Joules of energy. A charging All-Black has about 6000 Joules of energy. So energy would appear not to predict lethality either. How the projectile transfers it's momentum and energy to the target will matter. This depends on the 'area' hit. And the type of tissue hit. And the weight of the animal. And the speed of the projectile. And the weight of the projectile. And the construction of the projectile. And the shape of the projectile. A physicist/engineer would probably predict a good combination of all of the above, then get someone to test it by shooting lots and lots of animals to see what actually happened. A doctor/vet would probably ask "How big's the hole and whereabouts is it?!" All this has already been said by experienced people, I just thought it my be interesting to say it a different way. |
@ 03:38 pm (GMT) |
Craig SanfordRe: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?Euan really hit it out of the park with his comment. A baseball thrown by a major league pitcher at 99 mph has a higher Taylor KO Index than a 405-grain bullet from a .45-70 at 1,300 fps. TKO favors momentum and this example finds the obvious flaw in the TKO theory. Next let us consider that a 50-grain bullet from a .22-250 at 4,000 fps has more kinetic energy than the aforementioned bullet from the .45-70, yet energy figures are so often quoted as mathematical matches for certain hunting applications. I think we’ve all read/heard of the “1,500 ft.-lbs. minimum for elk” which seems arbitrary on further examination. It’s logical, intuitive, and obvious that no one is going buffalo hunting with a .22-250, much less a fast pitch baseball. Animals are killed by tissue destruction, blood loss, and shock. We can utilize bullet selection, velocity, energy, momentum, and shot placement to exact our desired outcome. This is precisely why one bullet may perform at 300 yards and another at 600 (perhaps not vice versa) when fired from the .280 as the example given in another recent thread. Nathan’s research proves it. |
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@ 05:20 pm (GMT) |
Scott StruifRe: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?You can count on Hornady ELD-M bullets to have the thinnest possible jacket thickness between their heavy, large caliber bulllets, and their light, small caliber ones. That’s what they said in their most recent podcast. Comparison of their terminal effects, based on mass and velocity, makes sense. If you bring other bullet construction variables into it, you can’t compare bullets based on any meaningful common denominator. For example, there’s no sense comparing a 180 grain Accubond to a 180 grain Interbond based on their weight. You can’t even compare a 30 cal Interbond to a 7mm Interbond of the same weight. The manufacturer plays with jacket thickness and shape to achieve performance in gel that they think the customer wants. Hornady said as much. |
@ 04:46 am (GMT) |
John StewartRe: Kinetic Energy and Momentum? What force is most predominant for the lethality of a cartridge?Quote: Hi DR015, I have been writing about this for some time now, to be published in an upcoming book. The subject cannot really be covered in a short forum reply.
The question is whether momentum or kinetic energy has the greatest effect on terminal performance. The answer is neither. Without taking the bullet shape and construction into account, any such model is simply theory. These days, people are using theory to prove scientific concepts without taking facts or evidence into consideration. Science has become an ideology, bordering on a new religion. The best way to determine the lethality of a cartridge is to test it on game. There is simply no substitute for this. An example of the effects of bullet shape can be found in my article, The effect of the meplat on terminal performance. https://www.ballisticstudies.com/Knowledgebase/The+Effects+Of+The+Meplat+On+Terminal+Ballistics.html Examples of the effects of bullet construction can be found throughout the knowledge base. Otherwise, you have already identified basic factors such as momentum being key to penetration on large bodied animals. See also: https://www.norma-ammunition.com/en-us/norma-academy/dedicated-hunting/ammunition/effective-game-killing The best way to summarize this is to quote past Hornady Ballistician Dave Emary. He has distilled this into one single accurate statement - "it depends". Hi again Nathan, I have been hunting for just over 50 years now, I have taken large British Columbia moose with 215 grain RN bullets out of my 303 jungle carbine, I have also taken them with 30-06, 308, 270, 250 Savage, 6.5 Creedmoor, (yup, 6.5 Creedmoor), 300 Savage, 7x57, 8x57, 6.5x300 Weatherby mag, 7mm mag, 45-70, 280 Remington (one of my favorites). Some of these cartridges listed were kind of slow like the 215 grain load from the 303, that bull soaked up two of these bulldozer slugs before he hit the dirt. Others were pretty spicy like the 6.5x300 Weatherby mag, I took a large bull moose with this one at a measured 770 yds. All of these cartridges had one thing in common, I used them within their limitations and placed the shot in the heart lung area, some required minimal tracking, most dropped right away or within a few feet of being shot. The best bullet is the the one that makes it to the vitals no matter the name on the box. Thanks again to Nathan for a very informative site, John Out here in rainy BC Canada |
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