quote:

ALF
one of us

Posted 16 February 2010 06:43 Hide Post
sofa sofa

Physics:

The study of matter

Rendering explanations regarding observations of our physical world (matter) or the interactions of matter with each other in our physical world to a logical mathematical model.

So for the problem at hand: The impact and behavior of a bullet (a dense solid) with a target and in the case of living tissue an admixture of matter with primary viscous and fluid behaviors. or perhaps paper layers of structurally firm materials with inviscid properties

Targets can be broadly classified as Structurally Hard, Structurally Firm with Viscous properties, Structurally Firm with Inviscid properties, Structurally Firm but with mainly viscous and fluid properties and finally structurally Soft with primary fluid properties.

In each instance the observer who wishes to model penetration of a projectile into each of these respective targets needs to give credence to the mechanical properties of each and include it in a particular mathematical model.

In short then:

1. We need to understand the physical nature of "state of matter" as it pertains to mechanical properties of both bullet and target

2. We then need to choose a logical valid mathematical model to describe what we are Observing?

Importantly the field of mathematics chosen much match the behaviors of the state of matter we wish to describe. If the model is based in linear mechanics then stick to linear mechanics, if the model is based on thermodynamics then the applicable math has to be applied.

For someone to say Energy is of no value, or sectional density is of no value and then to try to offer explanation by crossing ad lib from one mathematical model to another without correct mathematical consideration is illogical.

If we look at penetration mechanics we see that there are models that choose to view both the bullet and target as fluids ( Alekseevski - Tait equations) where projectile diameter and mass are of no consequence ie SD is discounted so too nose shape; the same can be said of hydromechanics models where the density of fluid and its vapour is of importance again nose shape of no consequence.... when a traditional newtonian linear mechanics model is used however diameter and mass and nose shape is all important.

One of the major failings in the world of terminal ballistics in the lay realm at least has been a failure to understand fully what we are observing or misapplication of an appropriate mathematical model.

So in reality not what we “think we are seeing” but truly understanding what we are seeing based on logic and physics that govern the interactions between states of matter.

The modern terminal ballistics movement of the 80’s, centered on both sides of the Atlantic, in no uncertain terms highlighted the flawed reasoning of centuries of “Lies, Damned lies and ballistics”

What is interesting though is that not only the lay hunting public but also academics where guilty of propagating ballistics pseudoscience.

It has not been that uncommon to see prominent medical Trauma textbooks and even police ballistics experts perpetrating error, not to speak of the lay hunting press written by self proclaimed expert hunters.

McPherson in his book Bullet penetration - Modeling the dynamics and incapacitation resulting from wound trauma Second printing, page 65 sums it up under the heading of “mystical effects”

This is of course not new, in fact it goes way back to the 1600’s when one of the fathers of ballistics, Benjamin Robins who invented the ballistic pendulum also ventured into the world of terminal ballistics.

Once Robins was able to measure velocity he set out to determine the relationship of velocity to penetration of ¾ inch steel balls fired from a musket into Oak.

The assumptions that followed were as some would say ? “part right, part wrong” , much like a lot of the flawed reasoning we see today in the lay ballistics literature.

At the time when Robins did his work he and others had not yet formulated the effects of drag in terms of the state of matter of the target.

The assumed relationship indicated that penetration had a linear relationship to impact velocity.
Based on his assumption then a “physical rule” was created.
Euler who translated and expanded on Robins ‘s famous book confirmed this relationship albeit flawed.

What is interesting is that this “rule” held for almost 200 years. What is more interesting was that the rule was tested and strangely upheld even though observations to the contrary were made when projectiles were fired into all manner of material, bordering then perhaps on McPherson’s realm of “the mystical”

What is abundantly clear today is that we need to define what phase of matter we are dealing with and when choosing a physical model to describe what we are seeing to make sure that the math fits to phase of matter.

To some issues raised here:

The aluminium bullet?

Not new at all in fact there are still some manufacturers that produce aluminium bullets. CDM A.S. of Mexico under the trade name Aquilla manufacture bullets made of Aluminium ( Cartouchos Deportivos de Mexico AS ) I believe Kynoch and others dabbled in aluminium bullets between the great wars, an attempt to add wounding capability to the diminutive 25 ACP and 32 ACP often used by covert agents in occupied countries.

The ballistic problem of the aluminium bullet falls under the forensics realm of “low Sectional density” or “low mass “ projectiles.

Because of the low SD relative to caliber these projectiles can be shot at much higher velocities than their “normal” SD counterparts giving them high impact kinetic energy values.

This then creates at least two physical problems.

The first is that because of the low SD these projectiles have very poor BC and their usable effective range is quite small when compared to “normal” bullets. So for rifles at least they are of little value

The second problem has to do with the impact mechanics of such a projectile in a visco-elastic target and then in particular the way the target handles the energy imparted to it.

Because of the high velocity these projectiles have higher drag than their “normal SD” counterparts and they then tend to shed all of their energy in the early parts of the penetration path.

As stated before the nature of matter of the target determines what the target will do with this energy in terms of creation of a wound.

If it were pure muscle ie a firm target with high viscosity and elasticity, the aluminium bullet would be quite ineffective because it would simply dump energy and the energy would be absorbed by the muscle without causing much damage beyond what is contacted by the bullet.

On the other hand if the target were dense with water like properties, say liver, one would get a massive wound. Liver when impacted by high velocity projectiles tends to lacerate with cracks radiating out beyond the permanent cavity.

If anyone thought such a liver wound would give a long lingering death or give cause for a long tracking before downing a game animal. Think again. The liver puts trough roughly 27 ml of mostly venous blood per kg of body weight, for a 70 kg animal it means a volume of 1.89 liters per minute. That means the animal of 70 kg will have lost 40% of it’s circulating blood volume within a minute after receiving a high velocity gunshot wound ! Unless there is a “animal” ICU out there that animal is toast !

In terms of the human target where the liver lies just behind an inch or so of skin muscle and fat these projectiles are devastating but only if dense vitals are hit, they do poorly in elastic targets such as lung or the gut.

In targets where substantial amounts of bone and muscle have to be traversed the aluminium bullets is quite useless More than often though they only produce very large shallow non fatal wounds and because of this have been banned from military use at least use under the Geneva convention.

What about kinetic energy? Again we need to go back to the basics of the physics at hand.
One of the oldest ballistics questions asked has been how much energy is absorbed by the target and how much and at what point in the bullet’s path?

What follows then also is how does this energy contribute to the wound, because after all is said and done based on the physics of thermodynamics it is this energy that will do the work that damages the target.

Extensive research has been done to try and solve this important question.

Energy dump per unit of distance travelled is not linear.
It is drag dependent and drag in turn is velocity dependent. Drag is also a function of the state of matter in which it is measured.

Then there is the whole debate about the flat nosed bullet?

What penetrates better, a perfectly round sphere or spheres that have had surfaces flattened ( the science of shotgun pellet penetration) and which has the least drag at all velocities ? a flat nosed cylinder or a sphere of similar caliber ? Which is more or less stable in flight? a pointy low drag bullet of or a FN bullet and what exatly stabilizes the bullet. Is it the FN per se or is it perhaps the distribution of mass relative to the CG and the point of wind pressure ? Perhaps the answers may not be what some will want to hear?

It basically brings us full circle to the opening lines of my statement !

We need to clear about the physics and the state of matter we are discussing and comparing.

quote:

Originally posted by ALF:


Physics:

The study of matter
(blah blah blah .. lots of disjointed but wordy things, mixing terms that are NOT related, but kinda sound cool together)

We need to clear about the physics and the state of matter we are discussing and comparing.

quote:

Originally posted by jwp475:

quote:

Originally posted by boom stick:
The rounded nose to meplat is to aid in feeding right?

It's only purpose. In the 1800 the great British Engineer Whitworth concluded the supiriority of the flat point for penetration.

Nothing new in the shooting world, it is only re-visited

quote:

On the other hand if the target were dense with water like properties, say liver, one would get a massive wound. Liver when impacted by high velocity projectiles tends to lacerate with cracks radiating out beyond the permanent cavity.

If anyone thought such a liver wound would give a long lingering death or give cause for a long tracking before downing a game animal. Think again. The liver puts trough roughly 27 ml of mostly venous blood per kg of body weight, for a 70 kg animal it means a volume of 1.89 liters per minute. That means the animal of 70 kg will have lost 40% of it’s circulating blood volume within a minute after receiving a high velocity gunshot wound ! Unless there is a “animal” ICU out there that animal is toast !

quote:

The aluminium bullet?

Not new at all in fact there are still some manufacturers that produce aluminium bullets. CDM A.S. of Mexico under the trade name Aquilla manufacture bullets made of Aluminium ( Cartouchos Deportivos de Mexico AS ) I believe Kynoch and others dabbled in aluminium bullets between the great wars, an attempt to add wounding capability to the diminutive 25 ACP and 32 ACP often used by covert agents in occupied countries.

The ballistic problem of the aluminium bullet falls under the forensics realm of “low Sectional density” or “low mass “ projectiles.

Because of the low SD relative to caliber these projectiles can be shot at much higher velocities than their “normal” SD counterparts giving them high impact kinetic energy values.

This then creates at least two physical problems.

The first is that because of the low SD these projectiles have very poor BC and their usable effective range is quite small when compared to “normal” bullets. So for rifles at least they are of little value

The second problem has to do with the impact mechanics of such a projectile in a visco-elastic target and then in particular the way the target handles the energy imparted to it.

Because of the high velocity these projectiles have higher drag than their “normal SD” counterparts and they then tend to shed all of their energy in the early parts of the penetration path.

As stated before the nature of matter of the target determines what the target will do with this energy in terms of creation of a wound.

If it were pure muscle ie a firm target with high viscosity and elasticity, the aluminium bullet would be quite ineffective because it would simply dump energy and the energy would be absorbed by the muscle without causing much damage beyond what is contacted by the bullet.

On the other hand if the target were dense with water like properties, say liver, one would get a massive wound. Liver when impacted by high velocity projectiles tends to lacerate with cracks radiating out beyond the permanent cavity.

If anyone thought such a liver wound would give a long lingering death or give cause for a long tracking before downing a game animal. Think again. The liver puts trough roughly 27 ml of mostly venous blood per kg of body weight, for a 70 kg animal it means a volume of 1.89 liters per minute. That means the animal of 70 kg will have lost 40% of it’s circulating blood volume within a minute after receiving a high velocity gunshot wound ! Unless there is a “animal” ICU out there that animal is toast !

In terms of the human target where the liver lies just behind an inch or so of skin muscle and fat these projectiles are devastating but only if dense vitals are hit, they do poorly in elastic targets such as lung or the gut.

In targets where substantial amounts of bone and muscle have to be traversed the aluminium bullets is quite useless More than often though they only produce very large shallow non fatal wounds and because of this have been banned from military use at least use under the Geneva convention.

quote:

This was a pretty neat medical explanation.

quote:

Liver when impacted by high velocity projectiles tends to lacerate with cracks radiating out beyond the permanent cavity.

quote:

Originally posted by michael458:
Good Afternoon Boys! I missed some of you today via phone. Sorry. I received 500 brand new .500 caliber 510 gr Solids yesterday afternoon, and had to put them in their place proper (JWP475 swears I am rolling naked in them, or accuses me of it anyway). Only a photo will tell the truth!

JWP475--got your message, good test, I agree, need someone to do us some bullets!

Been on the range the rest of the time, doing some cleaning up, bagging chewed up test medium, taking stock in what is left, and found I had just enough test medium left to conduct a little test today.

I have new test medium soaking overnight now and should be ready in the morning for the 416 caliber 400 gr Barnes banded tests! Be on the lookout Buffalo!

Y'all loaded some damn ugly photos today, blood and guts!

quote:

Glenn
What a nice bedtime story! LOL

quote:

Originally posted by someoldguy:

quote:

Glenn
What a nice bedtime story! LOL

Thanks.
I feel it actually is time for me to put it to bed, but I'll still be watching the results.
Not angry, just tired of the pissing contests and the pontificating and the pedantry. Guess that does mean I'm somewhat angry, but I don't really have anything of substance to offer other than interest.

Later. But I'll still be watching.

quote:

Is that correct foot orientation ...??

quote:

Glenn? bewildered PPP--Pissing-pontificating-pendantry! Whew!

Pay it no mind! Focus on the mission, the rest will pass by barely noticed! Anything of import will rise above the rest!

quote:

How you gentlemen should suffer unto those whom you know to be your betters. The learned wise ones that speak, not for their own lust gains but for our own good for we do not know the way. Ya, we are lost but for the golden tongue of the One that will lead us. Verily I say, seek out his council for the work is spoken. So it is said, so it is written, so it shall be done !!

quote:

Originally posted by ALF:
Someoldguy:

A tip perhaps

The formula for the distance it takes a spinning Projectile to become unstable can be found in Munks formula

To anwser your riddle of the distance it takes for the bullet to tumble. You need to figure out the following.

1. what effect the resistance this target has on the impact velocity of your bullet ie the coefficient of drag for this paper target..... I have to warn you though that the most common source of error in testing is because the target ia often inconsistant.

Tests done by various defence contracted authors all confirm, the biggest cause of inconstatant data lies with the consistancy of the target.

2. you need to know more about your bullets. Length, transverse moment of inertia and where the CG is

3. You need to know what impact angle of attack is ? so unless you have a high speed camera that can capture moment of impact and its set up so you ccan do the measurement . good luck

One you have all the data, some serious math follows and you come up with something that looks like this.

The constants are "target medium" dependent.


and graphs that look like this



or one can all skip it and simply go to the various journals of trauma nand forensics and find the various articles and reports done on the very subject