Some thoughts on bullet performance.

Started by gitano, November 09, 2004, 10:15:20 AM

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gitano

#15
NF,

I don't think anybody was denying the reality of a "shock wave" generated by the bullet. Rather I think there is disagreement on the effect of that wave, especially over a very short interval of time, say miliiseconds, or a longer interval of say seconds or minutes.
 
It is precisely this hydraulic wave that is the basis of my primary point regarding high-impact-velocity bullets. That wave represents a great deal of the converted kinetic energy of the bullet.
 
WRT to fish, maybe an explanation of what happens to fish exposed to underwater explosions will shed some more light on this subject. As an employee of the Alaska Department of Fish and Game, I personally conducted extensive experiments with explosives as a fish sampling tool. I was able to quantify the "effective sampling volume" based on the type of charge, the depth of the charge and the size of the fish to be sampled.
 
As most are aware, water is a non-compressable fluid. As such, it very effectively transfers energy over great distances. When an explosive device is detonated under water, most of the energy generated by the chemical reaction is transfered directly to the water, and most of that is tranfered very efficiently from the center of the explosion to any object in the water.
 
You can easily quantify the amount of energy available in the "shock wave" by using what is called the "inverse square spreading law". Simply put, it says that the amount of energy available in any AREA of the wave is proportional to the inverse of the distance from the explosion squared. Imagine a partially inflated balloon. Of course, there is a finite amount of "rubber" in that balloon. If you were to weigh one square centimeter of the partially inflated balloon, you would get, let's say 1 gram. Now inflate that balloon so that its radius is 2 centimeters more than it was in the initial condition. There is no more rubber in the balloon, but what rubber there is must be stretched over a larger surface, therefore there is less rubber per unit area. In this case, we have increased the radius by 2 units, therefore, we square 2 which is 4, and take the inverse which is 0.25. Therefore, a one square centimeter of the ballon would now weigh only 0.25 grams. This principle applies directly to our fish near an underwater explosion, or our deer's chest cavity. First to the effects on the fish.
 
A fish's body composition is almost indistiguishable from water. (Unless you want a detailed explanation of the truth of that, you'll have to trust me as a former submarine sonarman, and considerable addtional training and experience with fish and sound.) As such, as the hydraulic wave, WHICH IS NOT A PRESSURE WAVE BECAUSE WATER CANNOT EASILY BE COMPRESSED, contacts the fish, it simply passes through the fish as if it was just some more 'water'. However, we KNOW that fish are severely harmed or killed by underwater explosions. If they're "just like water", how could that be? Because many of them, and especially most freshwater fish, have gas bladders. A "gas bladder" is filled with - surprise surprise - gas. Gas IS compressable. And when the shock wave that is passing harmlessly throught the musculature and skeletal structures of the fish hits the gas bladder, seriously bad things start to happpen to the surrounding tissue. The air in the gas bladder gets compressed by the leading edge of the shock wave. As it hits the air, it velocity is slowed by a factor of approximately 5, from ~1500 meteres per second, to about 300 m/s. This is like hitting a "brick wall", and a great deal of energy is transfered to the fish. The leading edge of the PRESSURE WAVE (air is compressable, and it is being seriously compressed) is INCREASED pressure. Immediately behind (half a wavelength) the leading edge of the pressure wave, is the trailing edge which is an area of equally LOW PRESSURE. This transition between high and low pressure rips tissues apart if the amplitude of the difference between the high and low side of the PRESSURE wave is great enough. The amplitude is dependent on 1) how big the initial explosion was, and 2) how far the fish is from the "epi-center".
 
Now, how about that deer? Similar principles apply here, but an important difference is the source of the hydraulic wave. In our ballistic case, the source is an impact, just as the underwater explosion is an impact on the surrounding water. However, the source of the underwater explosion doesn't MOVE (unless you set it up to do so) like a bullet does. So the leading edge of the hydraulic wave (that is traveling at 1500 m/s through blood and muscle tissue) really causes no particular harm until it hits some gas/air like in the chest cavity and lungs. It is of course true that whatever blood is directly displaced by the bullet will send a "pulse" to opposite ends of what ever channel contains that blood - aorta, vena cava, etc. HOWEVER, the hydraulic wave DOES NOT cause blood displacement within a vessel. It cannot - it is physically impossible. What can and does cause blood displacement is the conversion of the hydrolic wave to a compression-rarefaction wave in a compressable fluid like air. Again, the high pressure leading edge, and the low pressure trailing edge can rend tissue depending on their amplitude. In this case, the amplitude is a funtion of the POWER transfered from the bullet to the animal.
 
And POWER is a force (ft-lbs or joules) applied over a distance (the deer's chest cavity) for some unit of TIME (the faster it happens the more power is dissipated).
 
Paul
Be nicer than necessary.

rockinbbar

Paul,

I agree that the power from the force of the bullet is delivered into the animal upon impact.
As I said you can slow down hunting videos & actually see the wave. Kinda like dropping a pebble in a still pond.

Do you think the sound wave that travels in front of a bullet has anything to do with impact force?
A bullet traveling mach 3 has a substantial wave in front of the nose of the bullet. I know if you shoot close to a light object, but not actually hit it....Like an empty alum. can, the can will be moved.

Also, back on track with the force of a bullet strike.....I very often shoot milk jugs & other bottles at 100 yards here at my range. If you set up several 16 oz. bottles, then shoot one, the force from the bursting bottle will knock down several others that are full.

Also, I shoot these bottles off of a stump where I nailed a 6' long board that is 12" wide & 1" thick....These boards don't last me very long. As I shoot the gallon jugs, the board will develope cracks after the impact of the bullet hitting several jugs. Then the force from the bullet striking the jugs compleatly splits the board, & I have to nail another one on the stump to hold the jugs.

Some fair amount of energy is being transfered to the wood when the force of the bullet striks the jugs.....Is is not an insignificant amount.

Can you relate the energy transfer I see with the cracking board to the energy released upon impact of the bullet hiting an animal?

Rockin'
Remind yourself often to SEE not just "look".

gitano

#17
This gets a little "sticky" here, mostly with terminology and a little bit of intuition.
 
When I first started experimenting with my 7x300 using 115 grain HPs, I put a 1 gallon plastic milk jug filled with water on top of a 55 gallon steel drum that was laying on its side. At the shot, the jug exploded, and the drum was bent in half with the edges of hte opposite ends 7" apart. That's a thumper. However, the "thing" that did the "damage" was NOT a PRESSURE wave with compression and rarefaction, because the water was not compressible. Instead, the force (foot-lbs) delivered by the bullet DISPLACED the water immediately surrounding and in front of the impact point. Being non-compressible, THAT water displaced some MORE. Ultimately, all of the energy of hte bullet was spent moving water. According to the law of conservation of momentum, the amount of water moved (mass), the speed at which it moved (velocity), and the distance it moved (distance) have to equal the energy the bullet was carrying. If "stuff" - like organs - get in the way AND CANNOT BE DISPLACED, they will either "withstand/absorb" the hit (convert the energy to heat and sound), or they get "distorted". It hurts to get your organs "distorted".
 
Since your board, like my steel drum, can't move with the applied force, it gets "distorted".
 
Paul
Be nicer than necessary.

CAfrica

Gitano,
 
Your explanation of the effect on fish opens up a new dimension. Possibly the "shock" is most effective in the lungs as the lungs are in essence a collection of tiny air pockets (alveoli). Wont these display the same effect you find in the air pocket in the fish? Especially since the alveoli are rich in capillaries which can be easily damaged.
 
HB, autopsies of animals do not confirm any "bursting of blood vessels" by the shock wave.  The only permanent damage is in the actual wound channel. Because an animal is not a uniform liquid mass, you cannot relate what happens to a water filled container to what happens inside the animal.  Also, blood vessels are not rigid, they "expand" to absorb pressure (that is why you can feel a pulse as the vessel expands to absorb the blood pumped by the heart). Obviously, in a small enough body (say a varmint) the body is unable to absord the shock and you do find that a high velocity impact will tear the body apart.  Similarly, a head shot on a varmint (shock contained inside the rigid walls of the skull) causes the skull to explode. A high velocity hit in the head on a varmint will totally disintegrate the head and you find the body without a head (I have shot many with my 220 Swift and have seen this).
 
The same way that a punch in the solar plexus will "paralyse" a person, the high velocity hit causes temporary paralysis.  This is a physiological reaction of the body, not "damage" done by the shock. (The best way to explain this is that the sudden "overload" of signals pucked up by the nerves, causes the brain to "malfunction" and the nerves "stop working" for an instant). If the bullet did not also physically damage vital organs, the animal that dropped so quickly will get up after a few seconds and run off (I am sure we will get many witnesses to this phenomenon, the "dead animal getting up" story).
 
 
Regards
 
C

Hunterbug

CAfrica, a few years ago I shot a doe mule deer with my 257 AI and a 100gr BT. My shot hit the left shoulder and the bullet was moving about 2900fps at impact. The bullet failed to penetrate the right side of the body cavity but when I dressed the animal the right shoulder was broken and there was bloodshot on the right side. The extreme amount of meat damage is one reason that I haven't used the Ballistic Tip since.
Ask not what your government can do for you. Ask how your government can go away and get out of your life.
 
 
The unarmed man is is not only defenseless, he is also contemptible.
Niccolo Machiavelli

CAfrica

Quote from: HunterbugCAfrica, a few years ago I shot a doe mule deer with my 257 AI and a 100gr BT. My shot hit the left shoulder and the bullet was moving about 2900fps at impact. The bullet failed to penetrate the right side of the body cavity but when I dressed the animal the right shoulder was broken and there was bloodshot on the right side. The extreme amount of meat damage is one reason that I haven't used the Ballistic Tip since.
HB, I have heard many such stories and personally have had a simlar experience, fortunately I shot a fairly small animal and the shot was still effective. The same bullet failure on a larger animal would have had a different result.  I now use only premium bullets in high velocity loads except for varminting.
 
My premium bullets of choice are solid copper HPs.
 
Regards.
 
C

22hornet

I know this is an old thread but gitano posted the link from another thread.

In trying to work out how much energy a projectile of any given calibre will deliver to an animal and trying to take into account the difference in calibre, .25 v's .35 for example, could you work on the formula of "pounds per square inch".
This might give some idea of how much pressure is imparted when the projectile strikes the target. It won't take into account the projectile expanding through the body though.
I had just thought of this after reading that the pressure a sharks bite is measured in p.s.i. (or tons per square inch.)
"Belief:" faith in something taught, as opposed to "knowledge:" which is awareness borne of experience.

gitano

That's not a bad idea as an objective measure of "whack" or "hammer", but you might want to take the inverse of it, because the larger the bullet caliber the smaller the "pounds" per quare inch are ging to be.
 
Let's take for example, a .257 and a .338. For the sake of this exercise, let's say impact energy (foot-pounds) is the same for both - 1000 ft-lbs to pick a number out of the air. The frontal area of the .257 bullet is 0.05187 square inches. The frontal area of the .338 is 0.08973 square inches. Dividing the 1000 ft-lbs of impact energy by 0.05187 results in 19,279 fot-lbs per square inch for the .257. For the .338, the figure is 11,145 ft-lbs per square inch - less than that of the .257. To get this 'right', the figures would need to be inverted. Doing so and multiplying by 1000, yields 8.97 square inches per foot-pound for the .338, and 5.19 square inches per foot-pound for the .257.
 
Paul
Be nicer than necessary.

22hornet

Quote from: gitano;92933[/SIZE]
To get this 'right', the figures would need to be inverted. Doing so and multiplying by 1000, yields 8.97 square inches per foot-pound for the .338, and 5.19 square inches per foot-pound for the .257.

Paul
[/SIZE]

You are right about inverting the figures. I should have worked that out. :o

And when you look at those figures, 8.97 v's 5.19 as a pertcentage, there is quite a difference. Whether the animal can tell or not is a different story, but it probably goes a way to giving us some idea of "calibre energy"

Maybe we should call this the "gitano effect" or g.e.?

How do the Flying Beer Keg numbers work out using this idea?
"Belief:" faith in something taught, as opposed to "knowledge:" which is awareness borne of experience.

bfrshooter

I do not believe in energy or any knock down formula. I believe in the work a bullet does in the animal. Whether it is to the nervous system or blood system. A bullets work needs to be tailored to the size of the animal and the penetration needed for a blood trail. Explosive high velocity bullets do not work and even slower expanding bullets will destroy meat. A balance must be reached for the game shot.
Shock can work very well but what if the shock wave does not reach a point where shutdown occurs? Over expansion with a tiny entrance hole and no exit also kills but will you find the animal? Non expanding bullets poke holes with no internal primary wound channels.
I have been working with revolvers and have found some interesting things. The .44, .45 and .475 with slow WLN and WFN boolits kill super fast with a great deal of internal damage. The same boolits in the 45-70 at a higher velocity are very poor with deer going 200 yards and very little damage to the lungs.
I have determined that the pressure wave in front of the faster boolit is forcing vital tissue out of the way into a secondary wound channel that collapses back to normal.  The primary channel is too small. This means I need some expansion with the faster boolit and the main reason is to slow the boolit in the deer for more "dwell" time but to also reduce the secondary wound channel.
It seems that under 1400 fps is ideal for a flat meplat boolit, hard cast. Over that velocity, expansion needs to be introduced.
Smaller calibers need more expansion but lighter boolits prevent penetration.
With a rifle you need to find expansion and also penetration to match game shot. Very important with small calibers. Large calibers for large tough animals can use less expansion or none at all.
Even though every bullet or boolit ever made can show sudden death or a long tracking job and maybe a lost animal, it is up to us to find a reliable combination that results in every animal being recovered without massive meat damage or the need to place every shot in the brain or spinal cord.  
Bullet selection is of the utmost importance.

gitano

I decided to wait "a while" to respond to this to let things calm down a bit first.

QuoteBullet selection is of the utmost importance.

It would be difficult to disagree more. I would say:

Bullet selection is of almost no importance.

Of such are horse races made.

Paul
Be nicer than necessary.

gitano

This is an old thread, but I found a video on YouTube that illustrates the point I make in post #16. You know what "they" say: A picture is worth a thousand words.

https://www.youtube.com/watch?annotation_id=annotation_1627981785&feature=iv&src_vid=Sl0BHueSjvA&v=W4DnuQOtA8E

Paul
Be nicer than necessary.

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