1. ## cartridge knockdown power

So, I just took an ewe at 275 yds with Hornady Interlock shot out of a 338 Win Man. I expected that she would just roll over and die after being hit that hard, but much to my chagrin that was not the case. Shot number two took care of the problem.
However, the Interlock did very little internal damage to the animal. THe shot entered her ribcage 3 ribs from the rear. It broke 3 ribs, and angled up and towards her stomach, taking out a lung, her diaphram, a stomach (I presume, as there was some grass around), and exited her belly. When I shot her the second time, I could see the exit wound from the first shot. It was a pinhole!
This all brings up an interesting point. I probably would have been just as well off to shoot that ewe with a .223, as very little energy was transfered to her body, judging by the wound.
I wonder if we were to begin considering the bullet velocity after exiting the target if this whole issue of "knockdown power" would go away. There are two ways of looking at this problem. THe first is via the energy loss of the bullet. The second is via energy gain of the target. WHat if the target has some inherit capacity to absorb energy, no matter how hard you hit it?
Let's consider ballistic gelatin. Let's say we have a 12" by 12" by 12" block of ballistic gelatin. A 45 Colt and a 454 Casull are loaded such that the projectile is identical, but that the 454 has significantly greater muzzle velocity. After the shots are fired, it is found that the channel made in the gelatin from each shot is identical.
Which block was hit harder? I would guess that that the amount of energy transfered to the gelatin by each shot was nearly identical. I would also expect that the projectile shot from the Casull exited the gel a a higher velocity. All that extra knockdown for nothing!
If you are shooting clean through your animals time and again, you are probably shooting more gun that you really need.
This is the work-energy theorem, and I have never seen it cited when discussing the relative knockdown power of different calibers. I find that odd, as nearly everone with a degree in math, the physical sciences, or engineering has been exposed to it.
Maybe the conversation should shift to the inherit capacity of a game animal to be knock down. Being relatively frail and thin, the bullet had less opportinity to transfer energy to this sheep, as opposed to a heavier animal such as a moose or a big bear. I wonder if game animals have some inheritly asymptotic capacity to absorb energy from a bullet wound, regardless of how much KE the bullet carries when it strikes the animal?
Thoughts?

2. ## Hornady performance on ewe

"THe shot entered her ribcage 3 ribs from the rear. It broke 3 ribs, and angled up and towards her stomach, taking out a lung, her diaphram, a stomach (I presume, as there was some grass around), and exited her belly. When I shot her the second time, I could see the exit wound from the first shot. It was a pinhole!"
AKSTEVE, I'm having trouble following the path of the bullet as you described it. If the bullet entered three ribs up, to break 3 more ribs, it would have to be running almost paralell to the sheep's body. You say it angled up towards the stomach and hit a lung and the diaphragm, seemingly meaning that it was traveling forward into the chest cavity, but then you said the bullet exited the belly.
Which Interlock were you using? Anything can happen with bullets upon hitting a game animal, but it surprizes me that after hitting three ribs, the bullet didn't have some upset, even at that range. I have been using Hornady Interlocks for many years, on bear, moose, deer and pig and never experienced what you say happened. But, like I say, anything is possible.

3. Yeah I'm having trouble figuring out the direction this bullet was traveling when the sheep was hit.

The lungs are in the fowrad section, but the belly is in the rearward section.

No mention of any liver damage.

4. Aside from the misterious bullet path, I think most hunters have a misconception about "knockdown." In my experience, there's probably no such thing with any kind of arm you would dare shoot from your shoulder. I've shot small deer at close range with a 458 Win Mag, and there was no sign that they were "knocked down." Sure a few collapsed in their tracks just like they do sometimes with a 243, but the concept of a bullet toppling an animal like a bowling pin is pretty thin. It can look that way when they are moving and stumble at the shot, but I'm not convinced.

With all that bone breaking, it wouldn't surprise me if the pinhole exit was a fragment of bone or bullet, rather than the whole Interlok. That makes even more sense when trying to explain all the internal damage- especially if the stomach is hit. We've all gut shot animals and had them remain standing for a while, which is starting to sound like what happened here. Unless you spend a lot of time elbow deep in goo, you aren't likely to recover many bullet fragments. Been there, done that, and hope never to do it again.

5. ## the point it is....

The bullet path or the performancne of the Interlock was not the salient point of the post. The post is about the amount of energy that a bullet can transfer to a game animal.

This is the first animal I've shot with the .338. I've shot plenty of sheep-sized animals with the '06. All but one of them piled up dead on the spot, and all suffered massive tissue damage. With this particular animal, I lost very little meat to the bullet wound, and there was very little bloodshot tissue surrounding the wound.

I am wondering if the issue of the inhereent ability of an animal to absorb shock is more relevant than the cartridges ability to deliver the shock.

The was a hole in one rib on the entry side, where the bullet struck the rib. The two adjacent ribs were fractured. The bullet proceeded laterally through the animal's chest cavity, but she was on an angle when I shot her and the trajectory was not normal to her spine. She was shot clean through, as there was about a 12 in diameter blood stain on the exit side of the wound.

6. ## Knock Down Power...

I'm with BrownBear on this. I have always resisted the term "knock down" power. I have said many times there is no such thing. I've seen many animals drop at the shot and many stand or walk away or run away with no sign of being hit and/or require another shot, even when the first was well placed with an adequate caliber.

With Marksmanship aside and given the most important aspect of the equation, I think several misconceptions are running rampant when this is discussed.

I have written many times about how I would prefer to have a good exit wound rather than have the animal "absorb" all the energy the bullet can deliver. I'll stand by that but it isn't that simple.

If you hunt with "solids" for a while you will see how slowly they kill. They do not do enough soft tissue damage to bring about a quick death. And even when shot through the most vital tissue. (heart, vena cava, aorta) animals still take longer to die than with a good soft point. Simply because the hole is smaller.

The problem with the soft point is it may expand too much too soon and stop before it reaches the vitals. (Expansion always reduces penetration.) A soft point, controlled expansion bullet is designed to expand X amount when it hits Z tissue at Y velocity. The velocity will usually vary in range of a few hundred fps and still give good performance. We have no control over the type of tissue it will go through but can err on the side of caution and say that a cape buffalo is tougher tissue than a dall sheep, but we can't really controll all the aspects of that. Certainly some of the dall sheep tissue is tougher than some of the cape buffalo soft parts. But in this case we would certainly want stronger built bullets for cape buffalo than for dall sheep. A general rule.

Another uncontrolled aspect is the impact velocity. We can know what the velocity is at the muzzle and at every ten yards out to 1000 but we can't control where the full curl will be found (never very close, huh?) Could I get you to back up about 50 yards, I don't want this bullet to expand too quickly. When impact velocity is too low the soft point may not expand or not expand as rapidly or to the point needed.

The bullet manufacturers are optimistic about how well their bullets behave but we should expect that. Also they test their bullets in some funny jelly like stuff not animal carcases. Your mileage may vary.

The only useful purpose for the energy the bullet has is to destroy tissue. Obviously it must be pointed at the tissue you want to destroy. And it must pass through all the non vital tissue between the outer skin and the vitals. If it does all this an added bonus is the exit wound. Also, the angle of the shot may present a little or a lot of non vital tissue for the bullet to transit through before reaching the vitals. These things must be considered. The nature of hunting is such we often have to track an animal after the shot, and a blood trail helps. But also, a larger exit wound, will facilitate a more rapid hemmorrhaging (larger than the entrance wound, usually) and hasten the expiration of the animal. Good soft points which expand and still penetrate will leave a much larger exit wound than any solid or non expanding bullet. Such as going up in caliber will do.

Given this as requirements, we still want a soft point expanding bullet because it is almost always a better hunting bullet than a solid, except for those calibers which donot have enough velocity to reliably expand and penetrate their bullets through the animal being hunted. Handgun calibers and any caliber when hunting Elephant and such. And that would be another debate as to when and where we would use "solids" and on what.

I would say that in the case of your sheep, the bullet did not expand or certainly not to the point we would have liked. Possibly beacuse of an angle and early contact with bone similar to hitting a tree limb. The bullet yaws and then does not receive the forces on which it relys to expand. (not nose on any more). Also at 275 yards the velocity of a 338 Mag is quite low (you didn't mention bullet weight or initial velocity) and a bullet designed to expand at 2800 fps in a brown bear probably won't expand much at 2300 fps in sheep guts.

I disagree with the 454 vs 45 colt gelatin block test. The added benefit of non expanding bullet penetration is from velocity alone. It is the opposite with expanding bullets, the higher impact velocity causes more rapid expansion and that decreases penetration. The solid wound would be deeper and the expanding bullet wound would be larger in diameter with higher velocity. In any hunting situation we must ballance these two, expansion and penetration, and match a bullet with velocity and animal and the range at which it is hunted. Certainly a good bullet design for sheep with a 243 would be different from a bullet design for a sheep with a 338 WM.

Also, your work/energy theorum must have an efficiency factor. How much actual work is being done vs how much energy is wasted by the elasticity of the tissue and other biological factors, as well as non damaging thermal conversion.

I once worked for a traffic radar manufacturer and we also made base ball radars. These are very similar to traffic radar, hand held and have digital readout. We got a request and ultimately a contract with an aircraft manufacturer in Wichita for a radar to measure the speed of a chicken at up to 600 miles an hour. Yeah, that's right a chicken. Anyway, I did most of the design for this modification to "check a chick speed" radar. Curiosity got me and while working on this I asked one of the A/C folks what is the deal and he explained it was for wind screen testing for bird strike resistance. We delivered them and they worked fine. It seems the live chicken was fired from a CO2 cannon into the wind screen material and clocked with the check-a-chick radar. They were looking for impact resistance up to 600 mph. Well the animal rights people got involved and got a court order to stop this torture of innocent chickens. So to continue the test the company was forced to resort to already deceased chickens and what more convient place to get a quantity than the local grocery store. Frozen chickens! The company was unable to build a windshield that could stop the over penetration of a frozen chicken even when fired at a low velocity of 300 mph. Live chickens are like soft points and frozen chickens were like solids, I guess.

7. I konw one of the chicken shooters, Murph. He says they finally settle on thawed chickens as the best compromise.

8. Much like that of energy vs. recoil vs. weight vs. accuracy vs. price, the amount of energy transferred to an animal is another compromise with penetration. If a person wanted to tranfer the entire amount of energy a bullet had they could simply use bullets designed to disengrate on impact and if a person wanted to use all available energy to penetrate an animal he or she could use a solid bullet.

These are the two extremes to this scenario and neither is acceptable for hunting purposes. With a complete energy transfer the bullet will not reliably reach the vital organs needed to kill an animal effectively as mentioned by Murphy. While using a solid bullet the bullet will generally penetrate more than what is needed and not do nearly the amount tissue damage it is capable of.

So the compromise somes in the form of having a premium hunting bullet that expands a certain amount in order to cause tissue damage and transfer energy, but also retains its weight in order to acheive adequate penetration.

The idea that a bullet should either stop just under the hide or exit the animal and then drop in order to achieve maximum energy tranfer is kind of bogus in my book. Hunting is never done in perfect conditions and a bullet and catridge designed to just barely fully penetrate a ewe, broadside, at 150 yards is going to do very different things on on a quatering away shot a 300 yards.

This is why I believe most people error on the side on too much gun rather than just enough. With premium hunting bullets meat damage is minimal and a person will want all of the extra energy when things are not perfect.

Now heres are my question/observation.
1. While using hard cast bullets many pistol and low energy catridges can achieve excellent penetration and because most are of calibers greater or equal to .429" they create a large and long wound channel, but everything I have read has led me to believe that they are inferior standard rifle cartidges in terms of "Stopping Power" or "Knockdown Power" even though the hard cast bullets might even create a larger and longer wound channel. I have not found anything that directy compares these types of cartridges. The Taylor Knockout formula trys to predict this, but I don't place much faith in the formula simply because a .44 Mag just about equals that of a 30-06 in terms of stopping power. (Have to throw the BS flag there) I remember reading something that tried to explain why a standard rifle cartridge has more stopping power than pistol/low energy cartridges using hard cast bullets and it had to do with the concussion and intial impact shock caused by bullets traveling at high speeds (2500 FPS+)?

Anyway if anyone wants to try and explain to me why large caliber hard cast bullets which cause a larger wound channel(theoretically) have less stopping power than standard rifle cartridges it would be greatly appreciated. Let me also state that I think that standard rifle catridges have more "stopping power" simply because there is more energy in play, but I would like to know what that extra energy does in terms of "stopping power".

Sorry for the length

9. In my experience, answering your question highlights another compromise: Bullet form. Rifle bullets tend to have a small meplat or none at all, a nod to more streamlined shape for better trajectory. Pistol bullets may have large meplats, simply because there is no illusion or aspiration for long range trajectory.

I've shot quite a bit of game with cast bullets of various shapes and designs. The few rifle bullets you can find with large-for-diamter meplats kill much more like handgun bullets, providing the kind of wound channel you describe. That's my biggest gripe against semi-auto pistol bullets of any diameter- they need a more or less round point to feed reliably, which compromises their effectiveness on game. Penetrate like the dickens, but slow killers.

Shot a deer broadside through the lungs one time with a 158 gr RN @ 750 fps from a 38 Special. Through and through penetration, and I tracked that sucker for 100 yards before finding him dead. Hard to even trace the wound channel. A couple of years later I coincidentally shot another with the same load, but topped with a 160 gr Keith. It didn't drop right away, as at higher velocities from a 357, but it still took only half a dozen steps before dropping. Wound channel was obvious.

Two dead deer don't prove a point, but it was enough to make me sympathise with any cop or service member forced to carry RN ammo.

10. ## wound channel

OK I'll give it a go...and hope I understood the question. The wound channel of a hard cast (might as well call it a "solid") pistol bullet traveling at normal pistol velocities is roughly the diameter of the bullet plus any tissue that collects around the bullet's nose plus maybe a very, very SMALL compression wave channel. The wound channel of a standard rifle bullet traveling at normal rifle velocities is NOT the diameter of the bullet whether it expands much or not. [A normal, expanding .30 caliber rifle bullet with an impact velocity of 2500+ fps that expands to .60 caliber will not leave a .60 caliber wound channel- the wound channel can be several inches in diameter] The wound channel with the rifle bullet is both the result of the bullet itself and the compression wave that surrounds it as it passes through tissue. In normal, non-bone tissue, the wound channel with the rifle bullet is roughly football shaped. With normal expanding bullets- the greater the velocity, the greater the rate energy is shed, the greater the size and/or intensity of the compression wave- the greater the diameter of the wound channel. The football-shaped channel can even become spherical in extreme cases. The harder the bullet, the less the deformation, the lower the rate of energy shed, the more elongated the football-shaped wound channel becomes. At rifle velocities the incompressable fluid (mostly water) which makes up the majority of the mass of animal soft tissue transmits the compression wave forward and outward as the bullet passes. This fluid incompressiblility and accompanying shear forces are what cause the tissue damage. Examine closely the wound channel of the next rifle-killed animal you clean and note the blood shot and shredded tissue surrounding the axis of the bullet path through the animal.

11. ## Cast Bullet Wounds...

George,

Very good comments. I would agree with an additional comment of the cast bullet shape, being a factor. Specifically, the meplat diameter. This more so than the diameter. The bigger the meplat, for a given velocity and weight, the larger the wound cavity. This flat large diameter blunt object driving through tissue creates more blunt force trauma. But as you pointed very little compression or "shock wave" if that is the term here.

Cast bullets seem to penetrate best, or reach their optimum penetration at velocities of about 1400-1800 fps due to two things. (This depends on stability, sectional density and diameter) The bullet will begin to rivet (deform) at hgher impact velocity and rapid deceleration causes the projectile to torque and yaw (wobble) at impact which destabilizes the bullet. Also at lower velocities there isn't enough energy and momentum to push it through the resistance.

Soft expanding bullets at higher velocity will expand and flatten at the nose. This shortens the bullet and aids it's stability. The large, expanded, high velocity bullet is more like the unexpanded cast with wide meplat but at higher velocity. Thus the wider wound cavity, from the compression wound.

Almost always, higher velocity at impact will make a larger (diameter) wound, and may or may not make a deeper one. Depending on bullet behavior. Of course there is always a limit to the maximum impact velocity that any bullet can withstand. Some bullets are very good at moderate velocity and others work well at screaming velocity. And hard cast seem to be better at under 2000 fps. Ah, well, lots of choices.

12. ## shearing

George,
Interesting point about shearing. I guess the wound channel is essentially "block shear", for lack of a better term. That depends on the ultimate strenght of the tissue being sheared and the perimeter of the wound channel times the length of the wound channel. Unfortunatley, there is wide fluctuation in the modulus of elasticity, the modulus of rupture, and the ultimate strength of animal tissue, making those numbers nearly impossible to predict to any meaningful end. That, and animals being mostly water, I wonder if this isn't more of a fluid dynamics problem.

No, there are no "efficiency factors" on work-energy, but there are negligible frictional losses associated with everything. THis is related to conservation of NRG (remember, NRG can be neither created nor destoryed. it goes somewhere!)

We have heard that we want an BIG exit wound. I like them too.

We have also heard that a hard cast bullet that doesn't open will penetrate better than a softer bullet that opens up. One would be inclined to believe that, all other factors being equal, more energy would have been transfered to my ewe had the bulled opened up more. Had the bullet opened more, I would have had a large exit wound, and the bullet would have had lower exit velocity. By work-energy, the bullet that expands more would have transferred more energy to my ewe.

Murphy, the frozen chicken vs. thawed chicken scenario is simple. The harder chicken had more inherent capacity to transfer energy to the glass (like a hard cast bullet) than the thawed chicken. The energy from the thawed chicken went into turning it into mush instead of breaking the glass.

I won't address the validity of work energy and the gelatin block example. Let's just say it's based on Newton's second law. I am inclined to trust 500+ years of scientific thought. That, and mankind had proved it countless times both theoretcially and emperically. We could write the proof if we like.

So where does this leave us? I think all posts are pointing towards the importance of 1) the largest exit wound possible and 2) transferring as much energy as possible to the animal.

Another question: We can control the mass of the projectile, along with it's other characteristics, and it's velocity. Do we prefer high velocity loads, or high mass loads?

13. ## bullet energy, etc.

Yes, can't deny the basic laws of physics- laws of conservation of energy and thermodynamics. The tissue destruction even goes beyond shear dynamics. Whew, this thread can really go to TMI ! But consider the bullet is spinning at something like 100 k rpm or more at impact. A soft lead nose and/or core can melt from friction as it strikes a material (even the air if going fast enough!). Colloidal-sized and larger particles/fragments of bullet are ejected beginning at impact and are blown or ejected radially from centrifugal force of the spinning bullet. These are called secondary projectiles and can exit the bullet's path axis at odd angles. This accounts for reports of shooting an animal broadside and seeing wound channels going wildly off axis. Also, there is rupturing of tissue at the cellular level surrounding the bullet- first the compression wave then the decompression, liquid to gas. A lot of this phenomenon has been called "hydrostatic shock" or hydrostatic shock effect for quite a few years. Never could get my brain around the use of the word "shock" so have always used compression wave- kinda like "knockdown power"- I just think in terms of tissue destruction or trauma. Trains and big trucks knock animals down, bullets don't and can't.

14. Originally Posted by George

A soft lead nose and/or core can melt from friction as it strikes a material (even the air if going fast enough!).

George I made that very same statement on 3 different Forums about 2 years ago and you should have heard the negative comments about such hogwash.

15. ## Federal TSX factory loads

Ok,
I believe we've missed the point of this string.
Let's put this kinetic energy idea into perspective. Here are the KE calcs for a Federal Factory load:

My 338 Win Mag:
A 225 gr Barnes X Triple Shock has a muzzle velocity of 2800 fps. The NRG is 3917 ft-lbs.
Here’s how I get there:
225 grains/7000 = .03214 lbs/32.2 = .000998 slugs.

The KE is
.5*.000998*2800*2800=3913 ft. lbs. The error between my answer and Federal’s is rounding due to significant figures.

Ok, that is easy enough. Any one want to argue with that?

NFL Linebacker:
400 lbs/32.2=12.42 slugs

If he is traveling at 25.1 fps is KE is as follows:
.5*12.42*25.1*25.1= 3913 ft lbs

Ok, so the KE from a 400 lb linebacker traveling at 25 fps is the same as the muzzle energy from this .338 Win Mag factory ammo. So, how fast is 25 fps?

25 fps/5280*60*60 = 17 mph

Anyone doubt that a 400 lb linebacker hitting my ewe at 17 mph wouldn't hit her like a freight train? Does anyone see the disconnect here?? Do we need to set up an experiment?

So, back to the point of the string...Does anyone know of any research done related to the inherint ability of an animal to absorb energy from a bullet? How about gelatin? Exit velocity studies? See what I mean when I say the energy differences between a .338 WM and a 375 H&H and a .308 for that matter is largely academic?

Thoughts?? How about the next obvious question....why doesn't that .338 bowl you over when you shoot it?

16. ## Hittin' Hard...

Ok Steve, we see you. Nice job with the math. Half the mass * velocity squared.

I think I would argue whether a 400# linebacker could achieve a top speed of 17 mph but not that he could tackle even a large ewe. I see your math works forward and backward. That's good.

This really isn't complicated at all. The linebacker is a larger caliber, heavier bullet, traveling at slower velocity. Larger diameter, flat nosed projectiles transfer more energy to the target.

My calculations for the linebacker would be the equivalent of a 3000 caliber bullet weighing 2,800,000 grains. Due to the wide meplat and flat frontal area, this projectile would transfer 98.47% of the 3,913 ft lbs of kinetic energy directly to the ewe. Ah....the medical term would be severe blunt trauma, contusions, adema and a concussion. The football term would be...ring her bell!

From the hunters perspective there would be extensive bruising and possibly blood shot meat. But it is my belief that after only a few seconds this ewe would rise on shaky legs and stumble off the field to the bench ....I mean the other side of the mountain and require a finishing linebacker or two. Also according to Newtons first law a ewe, which contains mass, when set in motion will continue in motion in a straight line until alter by an external force or field or linebacker.........

Why didn't the linebacker get a little ewe? Not enough sectional density.

Bullets with higher sectional density do more damage (penetrate deeper) than bullets with low SD.

Answer to your final question: Only a small portion of the 3913 ft.lbs. of energy is used to propel the rifle back into your shoulder. Neither you nor your ewe could take the full force through the rifle stock.

17. Just to keep things interesting. You can also consider the physiology of the animal at the moment of impact and the amount of hydraulic shock that is imparted by bullet impact on soft tissue.

If the heart is on the systolic stroke (maximum arterial pressure) a high velocity impact into soft tissue (mostly water) will spike the pressure possible causing instantaneous neural failure in the brain. You're typical BANG! - FLOP!, even though there is no apparent neural or major skeletal damage.

If the heart is diastolic (relaxing) the extra hydraulic pressure caused by bullet impact likely will not cause brain damage.

18. ## This is fun

I like where this thread is going. Can anyone run the numbers on whether the Seahawks' offensive line is adequate for Kodiak brown bears?

The question you pose that is of most interest to me, Steve, is whether there have been any studies of exit velocity.

The linebacker lacks the sectional density to penetrate the target. (Can you imagine the scene in the locker room otherwise? Yuck.) None of the bullets you mention have that problem, including those with wide meplats we've discussed.

Because the .308, .338, & .375 bullets all have sufficient sectional density not only to penetrate, but to carry energy out of the animal when they exit, we have little ability to assess how well any given animal "absorbs" bullet energy. Unless, as you suggest, anyone has done exit velocity tests. I'm sure not familiar with any.

But even if you could study how various media (gelatin, flesh, bone, sinew, skin, lung tissue, &c) respond to energy delivered by a given bullet at a given velocity, the other issues discussed by previous posters in this thread (e.g.: which tissue the bullet passes through on a given shot, bullet velocity at unpredictable ranges...) give us a sense of how many other variables there are. I think there are too many to be able to draw precise conclusions about transfer of energy.

I take it this was your point when you said, "the energy differences between a .338 WM and a 375 H&H and a .308 for that matter is largely academic."

I'm willing to agree where non-dangerous game is concerned. Carry enough cartridge that your bullet will penetrate to the vitals and dispatch the animal responsibly. If it's got sharp teeth and is charging me, on the other hand, I suspect I'll be glad I listened attentively to some of the debates about bullet energy, penetration, and width of wound channel...

19. ## "knockdown" or not

AK Steve
OK I'll give it a go also. I think there is a mixing of physics terms- a kind of apples and oranges effect. ENERGY of a bullet in ft lbs is not the same as MOMENTUM of a bullet in lbs ft/sec. [The Energy equation involves the SQUARE of the velocity.] The question in the last paragraph about recoil vs bullet energy. The amount of recoil momentum is always somewhat more than the momentum of the bullet. But for sake of this discussion they are very roughly the same. The same reason that recoil doesn't knock down the shooter is the reason the bullet doesn't knock down the animal.
Momentum is an amount of motion defined as M (mass) x V (velocity).
Example: 338 bullet hits animal (150 lb ewe) at 2000 fps velocity. So the weight of the bullet in pounds (is about .03) x the velocity at impact (is about 2000 fps) = 60 lbs ft/sec Momentum. If the bullet transferred all it's momentum into the ewe (ewe 'absorbed' all the momentum), in this example, the total velocity that would be imparted to the ewe would be 60 lbs ft/sec / 150 lb = .4 f/s velocity total applied from time of impact for the fraction of a second the bullet travels to a stop in the body. The .4 f/s isn't much and it should be easy to see why bullets don't knock animals down.
A 45 cal bullet with large meplat traveling at 50 fps would probably knock down a squirrel.

20. Originally Posted by George
OK I'll give it a go...and hope I understood the question. The wound channel of a hard cast (might as well call it a "solid") pistol bullet traveling at normal pistol velocities is roughly the diameter of the bullet plus any tissue that collects around the bullet's nose plus maybe a very, very SMALL compression wave channel. The wound channel of a standard rifle bullet traveling at normal rifle velocities is NOT the diameter of the bullet whether it expands much or not. [A normal, expanding .30 caliber rifle bullet with an impact velocity of 2500+ fps that expands to .60 caliber will not leave a .60 caliber wound channel- the wound channel can be several inches in diameter] The wound channel with the rifle bullet is both the result of the bullet itself and the compression wave that surrounds it as it passes through tissue. In normal, non-bone tissue, the wound channel with the rifle bullet is roughly football shaped. With normal expanding bullets- the greater the velocity, the greater the rate energy is shed, the greater the size and/or intensity of the compression wave- the greater the diameter of the wound channel. The football-shaped channel can even become spherical in extreme cases. The harder the bullet, the less the deformation, the lower the rate of energy shed, the more elongated the football-shaped wound channel becomes. At rifle velocities the incompressable fluid (mostly water) which makes up the majority of the mass of animal soft tissue transmits the compression wave forward and outward as the bullet passes. This fluid incompressiblility and accompanying shear forces are what cause the tissue damage. Examine closely the wound channel of the next rifle-killed animal you clean and note the blood shot and shredded tissue surrounding the axis of the bullet path through the animal.

Thanks George that was pretty much what I was thinking, but made much more sense the way you wrote it down. It does bring up another point Murphy mentioned that he witnessed that solid rifle bullets do a poor job of killing and animal quickly. I would assume that this is do to a small compression wave caused by the bullet not expanding at all upon impact (Is this a poor assumption?). With an expanding rifle bullet I would assume that almost total expansion occurs upon intial impact with an animal and because of this it causes a considerable compression wave from initial impact to just before it exits an animal.

This discussion has illustrated another compromise that I have never really considered. "Killing Power" vs "Knockdown Power" (read the following scenarios to see what I mean)

1. 400lb linebacker traveling 25 FPS strikes/hits a 150lb ewe. Transfers roughly 3913 ft lbs of energy to the ewe. I don't think it is a stretch to say that this transfer on energy will very rarely "kill" the ewe, but I also don't think it is a stretch that it would consistanly "knockdown" the ewe. Why? Because an enormous amount of energy was completely absorbed by the animal, but no considerable tissue damage occured and not vital organs word destroyed.

2. 600 grain arrow traveling 220 FPS strikes/hit a 150lb ewe. Tranfers roughly 65 ft lbs or less of energy to the ewe (depends on arrow pass through). Again not a stretch that this will consistantly "kill" the ewe, but almost never "knockdown" the ewe. Why? Because an arrow "kills" by effectively penetrating to the vital organs and slicing through them with a sharp broad head, but tranfers 1/10 of the energy of a .22 Hornet so of course there is no "knockdown".

I don't consider "knockdown" the end all and be all, but I do think that it should be considered. I mean there is a reason why people reccomend large caliber, high energy rifles when traveling in bear country. I would assume that most people reccomend these because there is much more energy at play.

My beliefs about "knockdown" power are pretty simple: The more energy transfered to the animal the more "knockdown" power of the round. Keep in mind though that this is only "knockdown" power, and not killing power. And to effectively kill an animal you need tissue damage and to detroy vital organs.

Anyways I will quit rambling and hope that my main point was illustrated by the two scenarios.

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