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Minimum Velocity Clarification

 
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  #22  
Old 09-12-2013, 07:28 PM
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Re: Minimum Velocity Clarification

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Originally Posted by Canadian Bushman View Post
Im not sure if i agree with your reasoning but i most certainly agree with your conclusion and i think thats what the purpose of this thread was aimed at. If not we have sure drawn attention to some particular characteristics of terminal ballistics that will give others something to think about.

Montana rifleman i enjoyed the discussion, if you would like to continue in pm or another thread im always honored to hear your opinions. For the time being i wouldnt mind hearing others comments and honestly im a little tired of typing.

Thanks again ill be watching the thread.
My pleasure!
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  #23  
Old 09-13-2013, 10:33 AM
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Re: Minimum Velocity Clarification

I want to point out an error in your description of the KE equation. It could be simple semantics but I feel clarity is best.

The formula posted is correct, KE = 1/2mv^2

It represents a logical fallacy to say that this is 1/2 of mass times velocity squared. When we do multiplication in a row like this, each value is multiplied together so mass isn't given only half value because velocity squared is also halved when we finish the calculation.

What I mean to say is, when using your intuition to guess at the importance of each variable in the formula, you should think of it as KE = (m x v^2)/2 so you don't mistakenly assign too little relevance to the impact of mass on the end result.

On the subject of momentum vs KE, both are simply tools that are often incorrectly used as general guidelines in killing power. In my earlier post I preferred momentum because it gives equal credence to both mass and velocity. Large caliber, poor/non-expanding bullets at low velocity are extremely lethal as proven all over Africa and right here in NA before the advent of smokeless powder. The KE figures on most of these cartridges are laughable compared faster, modern ones.

The most important thing for me is advocating that we cannot use either of these derived figures as a true measurement of killing power.

I'll give an obvious example of why this might be a bad idea. I'm picking on KE here only because I can't come up with a good example for momentum at the moment:
If we take a 22-250 Rem with a 50gr bullet launched at 3850fps we get 1645ft lbs of energy at the muzzle. This leaves 1200+ft lbs at 100 Yards, a figure I've often seen as "needed" for big mule deer.

I wish I could say I didn't have experience with what the 22-250 and such a light bullet isn't capable of on game that size, but I've had the "pleasure" of hearing a lot of stories (I work hunting retail) of lamenting hunters talking about their targets bounding off, leaving no blood trail and never being recovered. What went wrong? Not a very big hole and not very deep.

If we load up the same rifle with a 60gr Nosler Partition, the KE figures are almost exactly the same but we will see a much more favorable terminal result. I have locals that I have been unable to talk out of using their 22-250s that have at least stepped into the 55gr Fusions and 60gr Partitions and report good results from the change, even providing an exit wound in some cases. Maybe the hole is the same diameter as before, but now it's a lot deeper.
This shouldn't really tell an intelligent hunter anything, since we all know to choose cartridges and bullets that are suitable for the game we pursue based primarily on either personal experience or the experience of the hunting community around us. We can't rely on these formulas in a vacuum. I'm sure we all know that without me saying it.

New hunter's almost always ask, "What caliber do you recommend for deer/elk/moose/bear?". Experienced hunters usually suggest some bullets along with their pet calibers, do they not?

Canadian Bushman, the way you are using KE in my mind is perfectly correct. It is obvious you have weighed all the other factors you can (suitable cartridge size, suitable bullet construction) and are using it as a comparison between loads and/or calibers. After my whole speal, I have to admit I occasionally do the same. More often however, I am looking for a personal 2000fps breakpoint to determine my maximum range. I'm not experienced at long range hunting as of yet and this number coincides with where I am comfortable with accurate shot placement.
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  #24  
Old 09-13-2013, 12:39 PM
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Re: Minimum Velocity Clarification

There are two complications when comparing momentum to energy besides the effect of velocity on the actual momentum/energy figure.

First is direction of travel.
Energy is a description of kinectic energy regardless of direction.

Momentum is a description of an objects resistance to stop in one direction.

Bullets always travel two directions regardless.
Away and down.

In terminal ballistics or any collision there are two types. Elastic and inelastic.
Elastic collisions mean it was an ideal transfer of 100% energy. And momentum is conserved whether transferred or not.

Inelastic means energy was dispersed in multiple ways and was not transferred all in one direction. Usually dispersed as heat sound and deformation of materials. Therfore momentum is inconsistant and uncaculable.

Almost every impact a bullet has with an animal is an inelastic collision. Energy is always dispersed and so in multiple directions.

In my opinion energy better suits terminal ballistics and is why it is so commonly used to describe a projectile.
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  #25  
Old 09-13-2013, 12:43 PM
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Re: Minimum Velocity Clarification

Quote:
Originally Posted by Talkyn View Post
I want to point out an error in your description of the KE equation. It could be simple semantics but I feel clarity is best.

The formula posted is correct, KE = 1/2mv^2

It represents a logical fallacy to say that this is 1/2 of mass times velocity squared. When we do multiplication in a row like this, each value is multiplied together so mass isn't given only half value because velocity squared is also halved when we finish the calculation.

What I mean to say is, when using your intuition to guess at the importance of each variable in the formula, you should think of it as KE = (m x v^2)/2 so you don't mistakenly assign too little relevance to the impact of mass on the end result.
You are correct and good point. That said, velocity is still factored exponentially compared to mass in the KE equation and IMO is not a viable measurement of destruction and killing potential. It does give us a vauge relative reference of the bullet's potential but that is as far as it goes.

Let's take the 22-250 example. My 22-250 will shoot 53 Vmax bullets to 4100 fps. At he muzzle, that is almost 2000 ftlbs of KE which is 33% more energy than a lot of folks say is minimum for killing elk. At 125 yds, the KE drops to the magic 1500 ftlbs requirement for elk. I would not shoot an elk at any range with this cartridge/bullet combo. Let's load the 60 Nos Partition. Let's assume an MV of 3900. The KE numbers will be very clost to the 53 Vmax. The Partition will likely penetrate much better but do we really want to shoot a large bull elk with this combo? The small hole greatly increase the odds that the bull will run off somewhere never to be found.

Now let's look at the Nos ABLR and Berger 7mm 168. With an MV of 2600 fps out of a 7-08, they have about the same energy @ 300 yds as the 22-250 bullets do @ 25 yds. Which will be the more effective killer? At 700 yds they have a velocity of about 1870 and a KE of 1300. A well placed shot through the lungs will effectively kill a bull elk. @ 950 yds the velocity is about 1604 and the KE about 1000. The Berger will probably pencil through but the ABLR will expand and penetrate both lungs and likely exit. Although probably not a highly recommended shot, the odds are it will effectively kill a large bull and one I would choose over the 22-250 @ 25 yds.

A 210 gr hardcast flat nose 44 cal bullet fire @ 1200 fps from a 44 mag will have 650 ftlbs @ 25 yds. I would choose the 44 cal hardcast bullet with 1/3 the KE of the 22-250 bullets.

KE just doesn't cut it as a determiner of killing potential.
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  #26  
Old 09-13-2013, 02:40 PM
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Re: Minimum Velocity Clarification

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Originally Posted by MontanaRifleman View Post
A 210 gr hardcast flat nose 44 cal bullet fire @ 1200 fps from a 44 mag will have 650 ftlbs @ 25 yds. I would choose the 44 cal hardcast bullet with 1/3 the KE of the 22-250 bullets.

KE just doesn't cut it as a determiner of killing potential.
Thanks for digging up some more figures. I was running out of time before I had to leave for work!

Bushman, what merit is the dispersion of this energy into the animal vs. the creation of a hole? If you use a bullet like a Berger that explodes inside the vitals, it is not the KE that stops the organs' functions, it is the nasty spray of shrapnel; the holes.

Montana's 210gr hard-cast sure as heck doesn't put any energy into the animal, yet it will be dispatched very quickly. Anyone that doubts this should really see it first hand. A co-worker uses his 45-70 Marlin almost exclusively with hard-cast bullets at very moderate speeds with tremendous success on moose.

We would all do well to recall that the first truly long range firearms where in calibers like the 45-70 and it's larger cousins. The trajectories are terrible, the KE figures are terrible, but the leathality is proven.

Gosh we've trailed off-topic haven't we?

Minimum velocity, in my opinion, varies greatly on the intended target and the bullet's construction. I've somewhat guessed at 2000fps for my uses in my rifle. Obviously if you are out there with a 45-whatever you will have to use a different number that you arrive at through research or experimentation.

If Berger says 1800fps, I would use 1800fps with those bullets unless I had reason to think otherwise.
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  #27  
Old 09-13-2013, 03:02 PM
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Re: Minimum Velocity Clarification

Quote:
Bushman, what merit is the dispersion of this energy into the animal vs. the creation of a hole? If you use a bullet like a Berger that explodes inside the vitals, it is not the KE that stops the organs' functions, it is the nasty spray of shrapnel; the holes.
A bullet fragmenting and stopping inside an animal is indeed dumping energy. It is creating a large wound cavity, or a lot of small ones and a massive amount of surrounding tissue damage, trauma, resulting from extreme shock. This is precisely what berger advertises their bullets design is intended to do. Every animal i have shot where the berger performed as said was filled with mush. Not tissue with lots of holes in it, but mush. This is also reffered to as hydrostatic shock. Another highly debated topic that in my mind is a result of a intentionally deformed bullet dumping energy. Usually revealing itself as the damaged, blood shot, tissue surrounding the bullets entrance/exit. Hunting deer with lead buck shot is another fine example of this and a very efficient way to kill quickly.
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  #28  
Old 09-13-2013, 03:13 PM
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Re: Minimum Velocity Clarification

Quote:
Thanks for digging up some more figures. I was running out of time before I had to leave for work!

Bushman, what merit is the dispersion of this energy into the animal vs. the creation of a hole? If you use a bullet like a Berger that explodes inside the vitals, it is not the KE that stops the organs' functions, it is the nasty spray of shrapnel; the holes.

Montana's 210gr hard-cast sure as heck doesn't put any energy into the animal, yet it will be dispatched very quickly. Anyone that doubts this should really see it first hand. A co-worker uses his 45-70 Marlin almost exclusively with hard-cast bullets at very moderate speeds with tremendous success on moose.

We would all do well to recall that the first truly long range firearms where in calibers like the 45-70 and it's larger cousins. The trajectories are terrible, the KE figures are terrible, but the leathality is proven.

Gosh we've trailed off-topic haven't we?

Minimum velocity, in my opinion, varies greatly on the intended target and the bullet's construction. I've somewhat guessed at 2000fps for my uses in my rifle. Obviously if you are out there with a 45-whatever you will have to use a different number that you arrive at through research or experimentation.

If Berger says 1800fps, I would use 1800fps with those bullets unless I had reason to think otherwise.
Its not always about how much energy a bullet has but how much can be transferred to the intended target.

This was the sole purpose for the creation of the slow flying 230gn 45 ACP.

Flat nosed lead bullets are wonderful for hunting because there ability to deform, and there flat nose aids in the transfer of energy as well as initiating a very stable, straight traveling expansion, that in my mind creates an ideal wound cavity as well as tissue damage . Another interesting trait of these bullets is that the recovered projectile is usually half the weight of what was fired. If it is not it either hit bone and exploded or exited the animal wasting energy. For purely hunting, a lead wadcutter will probably be close to an ideal design. However they fly like a brick. I prefer my bullets pointed.
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