Calculating Permanent Cavity Wound Mass from Fackler Wound Profiles

[Bigslug]

Momentum. . .I think this thread has run out of it.

Honestly, I think this wound mass concept is a largely dry well. If we accept that a certain amount of penetration is necessary, and that temporary cavity is meaningless at handgun impact speeds, we find ourselves looking at nothing but narrow wound paths of about 1-2 centimeters in diameter. Not much to choose, really. At some point you get small enough that the "drain" for letting blood out and air in will be unacceptably slow at the process, but between about .30 and .45, it's all much the same.

I've also got some issues against discounting the last bit of the wound track. With any of them, but especially with the various "talon" type rounds, any forward movement is crushing, tearing, or cutting something that can bleed or reduce function. As a hypothetical, a cross-body shot that goes through the arm on the far side might cut the brachial artery causing bleed-out, or break the humerous, taking the fight out of that arm. Also, the spinal cord is encased in some fairly significant bone that I'll want the ability to get through, regardless of what came first. I'm therefore not about to say that energy of a bullet that exits the body is "wasted", but rather that it had the certainty to do everything I needed of it.

On one extreme, I've seen a police shooting video where I knew what the 9mm duty load and approximate hit location on the excited suspect were, and a single cardiovascular hit did the job as instantly as if Wile E. Coyote's Acme Anvil had landed on his head. For the opposite, I've seen a video where the suspect soaked up about a dozen, presumably equal quality duty loads and kept advancing, and it was obvious that he only went down because his brain ran out of blood and he got "sleepy".

You'll see plenty of it with hunting rifles that have significantly more steam than handguns - for every instant bang-flop, there are probably 3-5 equally killed animals that took up to ten seconds or 30-100 yards to realize they were dead and fall down.

In short, if you want certainty, you should bet on dishonesty from Congress. You certainly aren't going to find it in terminal handgun ballistics.

[dverna]

This reminds me of the old song...."Love and marriage...you can't have one without the other"

Both momentum and KE have mass and velocity in their respective calculations.

For some "silly reason", ballistics studies have gravitated to KE as a measure of effectiveness. I think it was Russian collusion.

Then some "scientist" declared a bullet that dumped all its energy in the target (thus expending 100% of its momentum and KE) was more effective.

But "the data" indicated a bullet that passed through and gave two holes to leak blood out of made tracking easier and might be a better bullet to hunt with.

The solution was simple. Create a bullet that expands enough to dump most of its energy/momentum into the target and still passes through. And the modern jacketed bullet was born!!!!

It could be driven to higher velocities ,and with greater accuracy than a cast bullet, plus be made to expand while retaining enough mass to achieve "adequate penetration".

In another "twist of fate", cartridges with "good bullets" and high levels of momentum and KE seemed to create bigger wound channels. Who'd of guessed?

Yet, identical shot placement of the same "good bullet" having excessive momentum and KE will give us a DRT result one day, and a 100 yard tracking effort the next.

Enjoy the "science and data"!

[44MAG#1]

Momentum is the causation of energy. Without mass and speed we would not have momentum and energy would be zero. Look at the rams being knocked down in IHMSA matches.

[Ramjet-SS]

I understand the science and physics. But it comes down to the simple idea of how much critical tissue was destroyed or disrupted from the projectile. CNS hits are frequently incapacitating. That said if the projectile causes severe hemorrhaging it may take some time for the target to succumb to the loss of blood O2 etc. trying to quantify with math is ok to start the real research is the circumstances and analysis of the instances weather it be on game animals , police shootings or SD or even mass shootings. Detailed analysis and review is the real science. Fun discussion just the same and choose wisely and shot placement can even overcome poor bullet design. Practice practice practice……

[M-Tecs]

That bowling ball just propelled down the lane by the person has a great deal of momentum and the bowler isn't knocked backward by the momentum. If that ball would hit someone it would make an impacting experience on the impactee.

You never played medicine ball games/exercises have you? Medicine balls weight about the same as bowling balls. I have thrown and caught many. Rules of physics still apply. It's still for every action there is an equal and opposite reaction. Bowling ball, medicine balls or bullet do not magically create energy.

[44MAG#1]

Very aware of medicine balls. They have to be moving to generate momentum. There is nothing magical because they are propelled by someone.
The momentum is immense. The faster they are propelled the more momentum they have. The more momentum they have the more knockdown power they have.
Just like the bowling ball the faster it moves toward the bowling pins the more knockdown power it has.
Momentum is a force to be reckoned with.

[charlie b]

I disagree over a thrown bowling ball being a 'knock someone over' thing. I have caught them before (yes, messing around in an empty bowling alley). Not a big deal. Medicine balls as well.

Same as a pitcher throwing a fastball. Loads of momentum but easily caught. And it might sting a little if hit with a pitch, but, it is not that big a deal. And, yes, I've knocked someone over with a baseball and a football. They were caught off balance and not expecting to be hit.

I think KE was used for many years because it emphasized velocity over mass. Something the mfgs could turn into profit by selling the next big deal cause it generated 100fps more velocity.

If you want to know the real momentum/KE effect of a bullet, talk to someone who has taken a round in the chest plate of their body armor, or even someone who has been shot without armor. I've known a few from my Army days. None I knew were 'knocked over' by the bullets. Most fell down, mainly cause they were diving for cover.

[44MAG#1]

I disagree over a thrown bowling ball being a 'knock someone over' thing. I have caught them before (yes, messing around in an empty bowling alley). Not a big deal.

Same as a pitcher throwing a fastball. Loads of momentum but easily caught. And it might sting a little if hit with a pitch, but, it is not that big a deal. And, yes, I've knocked someone over with a baseball and a football. They were caught off balance and not expecting to be hit.

I think KE was used for many years because it emphasized velocity over mass. Something the mfgs could turn into profit by selling the next big deal cause it generated 100fps more velocity.

Everyone is free to agree, disagree or stand somewhere in the middle. If you were just standing there and someone lobbed a bowling ball at you you would stumble, stagger, leanand a few other things.
Momentum keeps things going. No momentum and the object is standing still.

[M-Tecs]

The laws of physics are 100% predictable and repeatable and not really open to opinions. Energy/momentums is not magically created. Hollywood has lot of people believing a shotgun blast will blow a person hit by it back 20 feet. Reality is if it accelerate in 6 inches and it decelerates in 6 inches the energy transfer is the same subject to minor differences in the acceleration deceleration curve.

[44MAG#1]

The laws of physics are 100% predictable and repeatable and not really open to opinions. Energy/momentums is not magically created. Hollywood has lot of people believing a shotgun blast will blow a person hit by it back 20 feet. Reality is if it accelerate in 6 inches and it decelerates in 6 inches the energy transfer is the same subject to minor differences in the acceleration deceleration curve.

Bullets travel at such high speeds momentum is great. The faster mass travels the more momentum it has.

[M-Tecs]

Bullets travel at such high speeds momentum is great. The faster mass travels the more momentum it has.

How much momentum does a beam of light have?????? Once again as simple as I can make it.

If you are holding a 1911 45 ACP and fire it at another 1911 being held by someone else and you perfectly center the bore with your bullet the person holding the second 1911 will feel that same as the person the fired the first 1911 minus slight differences in the acceleration/deceleration curve

[44MAG#1]

How much momentum does a beam of light have?????? Once again as simple as I can make it.

If you are holding a 1911 45 ACP and fire it at another 1911 being held by someone else and you perfectly center the bore with your bullet the person holding the second 1911 will feel that same as the person the fired the first 1911 minus slight differences in the acceleration/deceleration curve

Does a beam of light have mass?
If it does how much mass does it have? What is the weight of it's mass
Ill let you and Pettyplace do that stunt with the 45 Autos. Be sure to video it and upload it to YouTube if someone survives.
It should get many views.people are trying to make light of momentum but it is real and deadly.

[M-Tecs]

people are trying to make light of momentum but it is real and deadly.

No most here have a basic understanding of the laws of physics and how it applies to reality. Others seem to apply magical/mythical prosperities to momentum while disregarding more import components of the equation.

[44MAG#1]

No most here have a basic understanding of the laws of physics and how it applies to reality. Others seem to apply magical/mythical prosperities to momentum while disregarding more import components of the equation.

The laws of physics are not kicking momentum to the curb. Momentum is one of the large building blocks of effective power. Power is what puts the whammo on the bad guy
Momentum is a key player.

[billmc2]

I normally don't pay much attention to things like this but I was surprised to learn that my class reunion this year would be 45 years since graduation. I mention that because I no longer have the text books and I need to pull this from memory and the rememberer ain't as good as it used to be.

The terms being thrown around need to be defined so that everyone is working from the same page. Potential Energy is stored energy, it is not currently in use; a potential to do work. Examples would be springs and powder. Kinetic Energy is a measure of work being done. Momentum and Inertia are basically the same thing; one is a scalar and the other is a vector. I forget exactly which one is which but a scalar just has a quantity while a vector has a quantity and direction. (You can look here for a definition https://www.britannica.com/science/scalar)

Momentum/Inertia is a measure of a Mass to continue along its direction (including being stopped) unless it is acted upon by some outside force.

Using my own terms, momentum allows the bullet to keep going in a straight line. I can think of an outside force that could interact with a bullet as it traverses a critter and that would be a bone. Being still and not moving is a type of inertia (this is where the equal and opposite reaction comes into play). If the bullet has more momentum than the bone has inertia, the bullet will overcome the bone and it will continue on but with a much reduced momentum because it was used overcoming the bone. If the bone has more inertia than the bullet has momentum, the the bone wins out and the bullet stops (I'm not considering a glancing shot which would redirect the bullet). Without enough momentum the bullet couldn't do its job (penetrate). More momentum than needed and you end up with a bullet with momentum remaining that is equal to that which it had to begin with minus what was used in the target, thus able to continue on.

The Potential Energy of the powder is converted to Kinetic Energy of the bullet. Until all that energy is used up, the bullet will continue down its path. A portion of the Kinetic Energy is used to propel the bullet (imparting momentum). Upon striking the target, the target begins draining energy from the total remaining in the bullet. If it is an expanding bullet, energy is used to expand the bullet while at the same time energy is being used to give momentum to the bullet. Due to the interaction of the bullet and target, the energy remaining at any given moment is less than the moment before until the bullet's energy reaches zero and it stops. Usually we never consider other means of energy use draining energy from the bullet but they are present. Friction is present and that generates heat. The heat generated is wasted energy but we can't avoid that. So all these things (the terms being discussed) are interrelated and depend upon each other. We also never discuss gravity but that too, comes into play. Gravity is a factor in Inertia.

(If you'll indulge me in an aside I wanted to comment on 44MAG#1 tag line. What you say about weight and mass is correct. It took me a very long time to differentiate between mass and weight because on our planet they equal each other. Move that same mass to another location (such as the moon) and, depending upon that locations gravity, the weight will change but the mass will stay the same. Because I never foresaw myself dealing with off world events, I was happy to go with the practical, that being they are the same thing.)

[pettypace]

Honestly, I think this wound mass concept is a largely dry well. If we accept that a certain amount of penetration is necessary, and that temporary cavity is meaningless at handgun impact speeds, we find ourselves looking at nothing but narrow wound paths of about 1-2 centimeters in diameter. Not much to choose, really. At some point you get small enough that the "drain" for letting blood out and air in will be unacceptably slow at the process, but between about .30 and .45, it's all much the same.

With a handle like "Bigslug," this borders on blasphemy!

Can it possibly be true that "between about .30 and .45, it's all much the same"?

On a good day a FMJ bullet from a .32 ACP might have a permanent cavity wound mass, by MacPherson's reckoning, of about 13 grams. On the other end of the scale, an expanded 230 grain XTP from a 1911 should easily crush four times that amount of tissue.

Both bullets have more than enough penetration to satisfy the FBI. Either might miss vital structures and fail to stop an attacker. On the other hand, either could instantly incapacitate an attacker with the chance hit of a vital structure. But the odds of that chance hit increase with the mass of tissue damaged. Of course, there are no guarantees. But a 4X increase in odds is too much to write off as "it's all much the same."

[44MAG#1]

billmc2 said
"(If you'll indulge me in an aside I wanted to comment on 44MAG#1 tag line. What you say about weight and mass is correct. It took me a very long time to differentiate between mass and weight because on our planet they equal each other. Move that same mass to another location (such as the moon) and, depending upon that locations gravity, the weight will change but the mass will stay the same. Because I never foresaw myself dealing with off world events, I was happy to go with the practical, that being they are the same thing.)"

Thank you. Mass has weight. Several on here, one supposedly highly educated said it couldn't be weighed.
It stemmed from me giving the CORRECT formula for giving energy.
When I used "mass" for weight in the formula.
I was determined to be ignorant bordering on stupid even.
When I finally showed mass has Newtonian weight and it is derived from kilograms it became suddenly quite. I asked that if mass has Newtonian weight and that kilogram weight is used in the formula where did the kilogram weight come from since mass cannot be weighed according to the high IQ guys? There is 2lb 3.273965oz in a kilogram
And that is 15,432.359687 grains. I could do some more figuring but won't.
I like to learn from you guys.
Keep it up. I need the help.

[pettypace]

I've also got some issues against discounting the last bit of the wound track. With any of them, but especially with the various "talon" type rounds, any forward movement is crushing, tearing, or cutting something that can bleed or reduce function. As a hypothetical, a cross-body shot that goes through the arm on the far side might cut the brachial artery causing bleed-out, or break the humerous, taking the fight out of that arm. Also, the spinal cord is encased in some fairly significant bone that I'll want the ability to get through, regardless of what came first. I'm therefore not about to say that energy of a bullet that exits the body is "wasted", but rather that it had the certainty to do everything I needed of it.

I don't remember exactly how MacPherson worded his explanation for discounting the last 3" of penetration. Certainly, the gist of the argument was simply that the bullet was going too slow to do full damage. MacPherson's penetration graphs don't go below 400 ft/s. But extending his curves backwards (by eyeball), it looks as though the final 3" of penetration might correspond to the velocity going from maybe 200 f/s down to zero. I think 200 f/s is in the same neighborhood as the velocity needed to break the skin.

Here's what Fackler said about the tail end of penetration shown in his wound profiles:

The permanent cavity of expanded handgun bullets is shown as the diameter of the expanded bullets throughout its entire penetration (Figs. 2, 4, 5, 8, and 11). This is a simplification that has proven misleading to some. Actually, the bullet disrupts tissue approximating the full diameter of the expanded projectile only during the first part of its path in most tissue. As the bullet slows, it crushes less tissue and pushes more tissue ahead of it. Near the end of its path, the bullet is stretching tissue by pushing it ahead, thus stretching it, and then tearing its way through it. This applies to most living soft tissues which are quite elastic. When tissue is thus stretched ahead of the bullet before the bullet perforates it, the hole the bullet will make is smaller than the diameter of the bullet. The simplification of showing the permanent cavity as the diameter of the expanded bullet was essential because the diameter of the hole in gelatin does not reflect the hole size found in most elastic soft tissues - which vary in their firmness and flexibility. The permanent cavity as shown in wound profiles of expanded handgun bullets is closely approximated by the hole they make in nonelastic tissue such as liver.


I can't say that Fackler actually sanctioned MacPherson's 3 inch "discount." But they were colleagues and at one point Fackler wrote and published a positive review of MacPherson's book.

In any event, MacPherson's 3 inch "discount" is not a recommendation for less penetration, but rather, encouragement for more. In calculating "MacPherson wound mass," the "discount" has its biggest relative effect on bullets with limited penetration and no effect at all on those that penetrate more than 18 inches.

[44MAG#1]

This along with VIRGEL will settle it all.
https://shootingthebull.net/blog/the...tation-factor/

[charlie b]

Roflmao