9mm vs .45ACP

[Tactical Jackalope]

^----- lmao

I guess "equality" is in the eye of the beholder? I prefer beauty in that saying but of well...

Like Hk and Hi-Point being cousins in looks.

SIG 1911 XO / SA 1911 custom / Colt Gold Cup / SIG P226 e2 / Browning High-power / Beretta PX4 Storm / G34 / G19 / G21 / G22 / G30 / S&W M-19 / Hk USP 40 / Rem 870 / Rock R. AR-15

sent from my Android

 

[481]

Bullet form factor is equal? No.

Mike,

Your use of - bullet form factor- makes me think that maybe? perhaps? you have read Quantitative Ammunition Selection ? Just wondering....

 

[Tactical Jackalope]

According to astronomy, when you wish upon a star you're actually a few million years late. The star is dead, just like your dreams.


::beating the dead horse::

SIG 1911 XO / SA 1911 custom / Colt Gold Cup / SIG P226 e2 / Browning High-power / Beretta PX4 Storm / G34 / G19 / G21 / G22 / G30 / S&W M-19 / Hk USP 40 / Rem 870 / Rock R. AR-15

sent from my Android

 

[Mike Irwin]

"Your use of - bullet form factor- makes me think that maybe? perhaps? you have read Quantitative Ammunition Selection ? Just wondering.... "

Nope. But I've read a number of British, French, and German artillery treatises over the years, mainly from the late 19th or early 20th centuries, when they were truly attempting to apply mathematics and science to artillery.

Many of the computations were based on a "standard form" projectile, and one of the paths of study was how altering the shape or weight of that projectile could dramatically alter its flight characteristics.

 

[Kevin_d77]

What if you shoot 9's out of your 45???? Best of both worlds!

 

[481]

I know that this waaaay off topic, but these might be interesting to you then, Mike.

http://www.eugeneleeslover.com/ARMOR-CHAPTER-XII-B.html

http://www.combinedfleet.com/formula.htm

 

[Mike Irwin]

Thanks, but I've read them both, Beast.

 

[481]

I should've figured as much.

 

[JohnKSa]

NOTHING, absolutely NOTHING, is even remotely close to "equal."

That's pretty close to the truth.

The only way all else would be equal would be if you were comparing two identical bullets.

Well, two identical bullets with differing weights and differing velocities--as long as the velocities are not TOO different.

For example, one could compare two bullets that are outwardly identical with identical hardnesses and structural integrities where one is made of a very light material and the other made of a very heavy material both fired at identical velocities. Momentum tells you that the lighter bullet won't penetrate as much as the heavier bullet because less mass at the same velocity means less momentum.

The same applies with two bullets that are totally identical when one is fired at a higher velocity. However, in that case you need an additional caveat since if the faster bullet goes TOO fast it can break up or deform which will introduce other factors that will heavily affect penetration. Assuming the faster bullet isn't going too fast then it will penetrate more because the same mass at higher velocity has more momentum.

If you can hold everything else equal other than mass and velocity then momentum can give you some useful information that relates well to penetration. Otherwise, the contribution due to momentum can easily be swamped by other factors.

Things get much shakier, but you can get reasonably accurate results when comparing bullets that have similar profiles and construction out of the same caliber even if they aren't completely identical. The more differences introduced, the less one can rely on momentum to tell the story.

The author has put together an interesting model based on momentum that can be used to calculate how far a bullet will penetrate, how much it will permanently crush and how fast it will be going if it exits a body part like a bicep.

Assuming it does even a halfway decent job at those predictions, it must take many other factors into account. If it doesn't, the predictions won't be worth much.

 

[481]

Assuming it does even a halfway decent job at those predictions, it must take many other factors into account. If it doesn't, the predictions won't be worth much.

Well, it's a little complicated for me to explain in a mercifully brief manner, but the author does a good job of it (taken from page 3 of the website) here-

"Using a projectile's average recovered diameter, weight, and impact velocity to predict its penetration depth and the mass of permanently damaged tissue within the permanent wound cavity, the quantitative model produces a tangible measure of any projectile's terminal performance, permitting the direct comparison of all types of self-defense ammunition."

and here from the first page-

"Based upon a modified fluid dynamics equation that correlates highly (r = +0.94) to more than 700 points of manufacturer- and laboratory-test data, the quantitative model allows the use of water to generate terminal ballistic test results equivalent to those obtained in calibrated ten percent ordnance gelatin."

I doesn't seem like he missed much, but you'll have to read it and decide for yourself.

 

[JohnKSa]

First of all, the author isn't trying to come up with a formula for predicting penetration, he's working on a formula to correct water testing figures so that they match gel testing figures. The water testing figures incorporate the "many factors" I was referring to--since it is actual penetration data, but provides a result that doesn't match gel testing results.

Second, even with the water testing figures as a starting basis, he still needs average expanded diameter in addition to momentum.

Basically, he's taking one kind of empirical testing data and has come up with a formula to convert that test data to a different kind of test data that's harder/more expensive to generate. His formula doesn't predict penetration, it MODIFIES one type of penetration data to match a second type of penetration data.

The key is that the water penetration figures have "contained within them" the effects of factors like the energy expended in expanding the bullets, the energy expended generating a temporary cavity, the tendency of a bullet to tumble, the rate at which expansion occurs, momentum, energy, and many other factors.

Coming up with a formula to convert those empirically obtained water penetration figures to match gel testing figures is tremendously different and far easier than coming up with a formula that actually generates accurate penetration data based on readily calculated and/or measured quantities like bullet diameter, mass, velocity, energy, momentum, etc.. It's certainly nothing like coming up with a formula that generates accurate penetration data using only momentum.

 

[481]

Second, even with the water testing figures as a starting basis, he still needs average expanded diameter in addition to momentum.

I never said that he didn't need an average expanded diameter. In fact, I included text copied from the 'site that says just that (see the first quote that I took from the 'site) as he explains thoroughly in the book.

Basically, he's taking one kind of empirical testing data and has come up with a formula to convert that test data to a different kind of test data that's harder/more expensive to generate. His formula doesn't predict penetration, it MODIFIES one type of penetration data to match a second type of penetration data.

Actually, the model appears to do both.

Of course, it converts data from one medium to another. It also predicts penetration- all you have to do is use the values of your choosing and you can predict what a round will do. In fact, the author states that testing fmjs and other non-expanding bullets in water is not necessary since they are highly unlikely to expand in water or soft tissue. Without any preceding test; that's a prediction- plain and simple.

Coming up with a formula to convert those empirically obtained water penetration figures to match gel testing figures is tremendously different and far easier than coming up with a formula that actually generates accurate penetration data based on readily calculated and/or measured quantities like bullet diameter, mass, velocity, energy, momentum, etc..

You make it sound so easy. I'm not so sure that it is. In fact, the model includes all of those "easily measured quantities", the notable exception being "energy".

It's certainly nothing like coming up with a formula that generates accurate penetration data using only momentum.

It appears that Mr. Schwartz has done just that.

Paraphrasing pages 17 and 18 of the book, the model is clearly explained as being derived solely from Newton's second law of motion, F = m ∆v/∆t = ma; the model uses momentum as its only basis- "∆v/∆t" being a function of the drag forces (F) and material strength effects (F) that the bullet (m) is subjected to.

All of Newton's three laws of motion are based upon and have to do with momentum. The first law, the law of inertia, the second law (F=ma), and the third law (conservation of momentum: mv = mv)- they are all about momentum.

A question for you- Have you had a chance to read the book or are you just going from what you've read here?

 

[Crow Hunter]

http://www.policemag.com/Channel/Patrol/Articles/2012/02/Shots-Fired-Skokie-Illinois-08-25-2008.aspx

More info to "fan the fire".

From what I understand, the officer involved has since switched to a G17....

 

[pete2]

As I see it , the bottom line is the 9 will kill jello just as well as a 45??????

 

[Nanuk]

First of all, the author isn't trying to come up with a formula for predicting penetration, he's working on a formula to correct water testing figures so that they match gel testing figures. The water testing figures incorporate the "many factors" I was referring to--since it is actual penetration data, but provides a result that doesn't match gel testing results.

Second, even with the water testing figures as a starting basis, he still needs average expanded diameter in addition to momentum.

Basically, he's taking one kind of empirical testing data and has come up with a formula to convert that test data to a different kind of test data that's harder/more expensive to generate. His formula doesn't predict penetration, it MODIFIES one type of penetration data to match a second type of penetration data.

So to put politically correct - he is making it up.

 

[JohnKSa]

Actually, the model appears to do both.

No, the abstract is quite clear, it only predicts in the sense that allows one to convert water penetration data to gel penetration data which is harder to obtain for the average gun owner.

QUANTITATIVE AMMUNITION SELECTION presents a mathematical model that allows armed professionals and lawfully-armed citizens to evaluate the terminal ballistic performance of self-defense ammunition using water as a valid ballistic test medium.

Based upon a modified fluid dynamics equation that correlates highly (r = +0.94) to more than 700 points of manufacturer- and laboratory-test data, the quantitative model allows the use of water to generate terminal ballistic test results equivalent to those obtained in calibrated ten percent ordnance gelatin.

The quantitative model accurately predicts the permanent wound cavity volume and mass, terminal penetration depth, and exit velocity of handgun projectiles as these phenomena would occur in calibrated ten percent ordnance gelatin and soft tissue.​

It's all predicated on having water penetration data available.

You make it sound so easy. I'm not so sure that it is.

I didn't say it was easy, I said it was FAR easier than trying to predict penetration figures with absolutely no penetration data to start from. It's not easy to come up with the method for doing the conversion, but it's essentially impossible to generate accurate penetration predictions in the general case without any penetration data of any kind to start from.

A question for you- Have you had a chance to read the book or are you just going from what you've read here?

I'm going from what the advertisement claims about the book, which should be sufficient.

After all, if a person came up with a way to cure cancer and wrote a book about it, he'd put that in the abstract instead of mentioning that he had a way to slightly improve the chances of surviving cancer and forgetting to say anything about the biggest part of his discovery.

Nothing in the advertisement/abstract/FAQ implies that it is possible or claims that the formula is able to generate accurate penetration predictions based on easily measured quantities without the availability of water penetration data.

It's essentially incredible that anyone would somehow neglect to make the most useful and significant part of his work clear in the advertisement for it.

The answer to one of the FAQs explains the purpose of the book very clearly.

Because water produces dynamic forces on transient projectiles that are nearly identical to those produced by calibrated ordnance gelatin, it is an excellent tissue simulant. Water is insensitive to ambient environmental conditions, requires no calibration in order to produce valid test results, and can be used with little difficulty. Ballistic tests conducted in calibrated ordnance gelatin require rigorous environmental control to ensure a valid test outcome and can cost in excess of $400 per test shot. The ease of use and low cost of testing in water make it an attractive option for those individuals seeking a valid, cost-effective ballistic test medium.​

Paraphrasing pages 17 and 18 of the book, the model is clearly explained as being derived solely from Newton's second law of motion, F = m ∆v/∆t = ma; the model uses momentum as its only basis- "∆v/∆t" being a function of the drag forces (F) and material strength effects (F) that the bullet (m) is subjected to.

Sure, that's highschool physics stuff. The problem is that the drag forces and material strength effects are essentially impossible to calculate from easily measured parameters like energy, velocity, bullet diameter, etc.. You have to have some sort of empirical data, provided by water penetration testing in this case, to give you some inkling of how to quantify those things.

So to put politically correct - he is making it up.

Not at all. I can't see that he's making any claims that are false. There are one of two options. Either his model isn't very accurate, or he's using a lot more than just a few easily measured parameters to make it work.

 

[JohnKSa]

Ok, bought the ebook version and read about the first 3/4 of the book.

He is claiming to be able to predict penetration for non-expanding bullets using impact velocity, impact weight, and bullet diameter. That's the simplest case, of course. From what I can see in his examples, the numbers he provides aren't way off base, but they are somewhat optimistic, which is a given since his model can't (and doesn't make any attempt to) take things like bullet tumbling into account. That's a factor which can certainly limit penetration, and one that is fairly frequently encountered.

He also claims to be able to predict penetration for expanding bullets using impact velocity, impact weight, retained weight and average expanded bullet diameter (expansion and retained weight based on firing into water). Again, his model assumes that the bullet goes straight through the tissue without tumbling, he also makes assumptions about the speed with which expansion takes place. It's probably better than simply making a WAG, but his model essentially says that all expanding bullets of the same caliber and initial weight that expand to the same size and hit with the same impact velocity and retain the same amount of weight will all penetrate identical amounts. We know that's not true from looking at penetration data. His figures do get you in the ballpark though, especially for lower tech ammo.

In addition, he's using the water testing to expand the bullet and to obtain the retained weight figure. That's providing information that's not measurable without some sort of empirical testing.

I suspect the newer engineered expansion ammo is going to give his model fits.

 

[481]

Ok, bought the ebook version and read about the first 3/4 of the book.

Well, there's a start. It's difficult to take anyone's commentary on a book seriously if they have not bothered to read it.

He is claiming to be able to predict penetration for non-expanding bullets using impact velocity, impact weight, and bullet diameter. That's the simplest case, of course.

Of course, it is.

The model also allows the user to examine as he pleases hypothetical conditions such as when a JHP expands to a very high degree and/or sheds a large portion of its weight.

From what I can see in his examples, the numbers he provides aren't way off base, but they are somewhat optimistic,

This sounds like conjecture.

Based upon what information? Do you possess the academic/professional experience and/or a suitable data base upon which to support such an assertion?

...which is a given since his model can't (and doesn't make any attempt to) take things like bullet tumbling into account. That's a factor which can certainly limit penetration, and one that is fairly frequently encountered.

The evolution of hydrodynamic instability (tumbling) is a highly unpredictable behavior. I doubt that there are many one-dimensional models that can anticipate, let alone account for, such behavior without becoming extremely complicated and beyond the reach of almost everyone. FEM (finite element analysis) programs can't handle that type of behavior- it would be ridiculous to expect one dimensional models of this type (Schwartz's, MacPherson's) to predict it. He makes no claim that it can.

He also claims to be able to predict penetration for expanding bullets using impact velocity, impact weight, retained weight and average expanded bullet diameter (expansion and retained weight based on firing into water). Again, his model assumes that the bullet goes straight through the tissue without tumbling, he also makes assumptions about the speed with which expansion takes place. It's probably better than simply making a WAG, but his model essentially says that all expanding bullets of the same caliber and initial weight that expand to the same size and hit with the same impact velocity and retain the same amount of weight will all penetrate identical amounts. We know that's not true from looking at penetration data.

We agree.

All models make assumptions and will produce the same results if presented with the same inputs. To expect otherwise is naive. On the other hand, it is in error to damn a model simply for producing the same result from identical inputs. F will always equal ma. MV will always equal MV.

His figures do get you in the ballpark though, especially for lower tech ammo.

This makes no sense. "Lower tech ammo" (whatever that is), is the only ammo subject to the laws of physics? Aw c,mon, John. You can do better than that.

In addition, he's using the water testing to expand the bullet and to obtain the retained weight figure. That's providing information that's not measurable without some sort of empirical testing.

Sure, that's another part of the model's predictive function. There is nothing wrong with that.

I suspect the newer engineered expansion ammo is going to give his model fits.

That's extremely speculative.

Why? Is the "newer engineered expansion ammo" somehow immune to physical law?

Or is this just more conjecture?

Sure, that's highschool physics stuff. The problem is that the drag forces and material strength effects are essentially impossible to calculate from easily measured parameters like energy, velocity, bullet diameter, etc..

Nonsense. You cannot calculate an intrinsic property like material strength from the energy, velocity, diameter of a bullet- the material is as strong as it is and can be no more or less than what it is. The bullet may damage the material, but it doesn't define or alter its intrinsic properties. A bullet's energy has nothing to do with how strong a material is. A material is simply as strong as it is.

You have to have some sort of empirical data, provided by water penetration testing in this case, to give you some inkling of how to quantify those things.

Check out the website. It's not water-based data that he relies upon to support the model's validity- it's based upon independent lab and manufacturer data. The author states clearly that the model...

...correlates highly (r = +0.94) to more than 700 points of manufacturer- and laboratory-test data

Not at all. I can't see that he's making any claims that are false.There are one of two options. Either his model isn't very accurate, or he's using a lot more than just a few easily measured parameters to make it work.

Holy "double-talk", Batman!

He says that all you need to use it is the bullet's expanded diameter, velocity, and recovered diameter and he explains it all in the book. So now he's either a fool or a liar?

In all fairness, there's a third option that you've failed to mention- his model may be an accurate representation (r = 0.94, n = 700+) and he has been truthful about the parameters needed to make it work.

Would you also be so bold as to call Duncan MacPherson (his model has an n = 400+) a liar or a fool, given that he and Schwartz have both produced such models?

 

[JohnKSa]

This sounds like conjecture. Based upon what information?

Based on comparison of his examples to gel testing figures available on the web.

The evolution of hydrodynamic instability (tumbling) is a highly unpredictable behavior.

That's my point exactly. It's also a fairly important factor in penetration since it effectively, and randomly, changes the "frontal area" of the projectile by presenting a different frontal profile as the bullet changes orientation.

On the other hand, it is in error to damn a model simply for producing the same result from identical inputs.

The point is that simply because the listed factors are identical doesn't mean the bullets are identical nor that they will penetrate identically.

In other words, if one is comparing two outwardly identical bullets to determine which one will penetrate more, the model can't do it. In fact, that's a large part of what comparison testing is all about. If I have a 9mm carry gun that shoots to point of aim with 124gr bullets, I'm not interested in how .45ACP 230gr penetrates. What I want to know is how various expanding 124gr 9mm loadings compare.

The model can't really do that because of the limited inputs to the model. That's not because the model is improperly constructed, it's going to be a limitation of any model that attempts to generate penetration figures with such limited input.

This makes no sense. "Lower tech ammo" (whatever that is), is the only ammo subject to the laws of physics?

Lower tech ammo is easier to characterize and easier to make accurate assumptions about. For an extreme comparison, a non-expanding round can be characterized much more easily and the assumptions about it will be much more accurate than the characterizations of and assumptions regarding a high-tech engineered expansion round.

Nonsense. You cannot calculate an intrinsic property like material strength from the energy, velocity, diameter of a bullet- the material is as strong as it is and can be no more or less than what it is. The bullet may damage the material, but it doesn't define or alter its intrinsic properties. A bullet's energy has nothing to do with how strong a material is. A material is simply as strong as it is.

He's skirting some of this because you get some of the information wrapped into the expansion figure of the bullet.

It's true that a bullet is what it is, however, his model makes no attempt to carefully characterize the material strength of the bullet, so the only thing his model "knows" about the bullet is what can be externally derived from the expansion figure. It's essentially equivalent to hitting a bullet with a sledgehammer and then trying to determine from the results the exact material strengths and properties from how the bullet looks afterwards. There's obviously some information in the appearance of the smashed bullet, but it can't tell the whole story.

It's not water-based data that he relies upon to support the model's validity-

I didn't say it was. What I said was that for the model to have a chance of succeeding, he needs data to input to the model from water-based testing and that is true. What I didn't understand before reading the book was that he wasn't even using penetration figures from the water testing, he's only using the expanded bullet diameter created by firing into water.

his model may be an accurate representation (r = 0.94, n = 700+)

What that figure means is that the model produces values that do a good job of tracking, but not necessarily matching the values from gel testing.

In other words, if his model says one bullet penetrates more than another, the high correlation between the two data sets means that gel testing is very likely to provide the same comparative result. It doesn't necessarily mean that all of the actual figures match each other very closely.

Good correlation means that if one plots the two data sets, the graphs have the same basic shape. In other words, if a value in one data set is large relative to other values in its data set, the corresponding value in the other data set is also large relative to other values in its data set, and vice versa. It does tell you important things about the relative sizes of things in one data set (assuming you know the corresponding values from the other data set), but it doesn't necessarily mean that the corresponding values from the other data set are closely matched in magnitude.

He says that all you need to use it is the bullet's expanded diameter, velocity, and recovered diameter and he explains it all in the book.

The expanded diameter is the result of actually firing a bullet into a penetration test medium. He has to have some sort of emprical data to start from--he doesn't just start from easily measured parameters like velocity and weight and the values that can be calculated from them like energy and momentum. Without some sort of actual test data from firing a bullet into a penetration medium you're limited to simple cases like non-expanding rounds that don't tumble.

 

[481]

In other words, if one is comparing two outwardly identical bullets to determine which one will penetrate more, the model can't do it. In fact, that's a large part of what comparison testing is all about. If I have a 9mm carry gun that shoots to point of aim with 124gr bullets, I'm not interested in how .45ACP 230gr penetrates. What I want to know is how various expanding 124gr 9mm loadings compare.

This is nothing less than a rewording of the statement that you made in an earlier post #157 (on page 7) in this thread-

"It works great for comparing bullet penetration, but only assuming that everything else is equal."

-that required wholesale correction by Mike Irwin in post #160 (also on page 7) and remains incorrect as repeated here. Schwartz's model clearly allows the entry of differing bullet weights, velocities and recovered diameters which would produce entirely different yields. Your premise which amounts to "all else being equal" vis-a-vis "two outwardly identical bullets" is simply a gross over-generalization that you've elected to take on its face as being factually accurate. It is not and the argument offered falls because of that.

If you apply the model to a .45-caliber 230 gr. FMJ at 850 fps and a 9mm 124 gr. FMJ at 1120 fps, both of which are "outwardly identical", the model says that the 230 gr. FMJ will penetrate to a depth of 25.38 inches and that the 124 gr. FMJ will go 27.87 inches.

It also works equally well with JHPs that have an "outwardly identical" appearance. A 9mm 124 gr. JHP @ 1120 fps that expands to 0.65" should go 9.51 inches, a .45 ACP 230 gr. JHP @ 850 fps that expands to 0.65" should go 14.58 inches.

In each case and despite your claim to the contrary, the model can tell which round will penetrate more even if they are "outwardly identical".

It's true that a bullet is what it is, however, his model makes no attempt to carefully characterize the material strength of the bullet, so the only thing his model "knows" about the bullet is what can be externally derived from the expansion figure. It's essentially equivalent to hitting a bullet with a sledgehammer and then trying to determine from the results the exact material strengths and properties from how the bullet looks afterwards. There's obviously some information in the appearance of the smashed bullet, but it can't tell the whole story.

That's an awfully huge misrepresentation, John.

The website clearly indicates that...

The quantitative model operates under three conditions:

1. All significant plastic deformation of the projectile occurs within periods of 10 ^ -4 seconds.

2. The projectile behaves as a rigid body after expansion (no further ductile or ablative erosion occurs) and exhibits no significant yaw during any portion of the penetration event.

3. The terminal behavior of the projectile is governed by a material strength variable and the inertial and viscous (or frictional) drag losses that occur during the projectile's penetration through the medium.

There is no need to include the material strength of the bullet because it is immaterial once the nearly instantaneous expansion of the bullet comes to an end. Both Schwartz's model and MacPherson's model operate under this condition and it is a valid position. I have to defer to the greater sum of their collective knowledge (not to mention the munitions engineer that endorsed Schwartz's model on page 2 of the website) in this case.

What I didn't understand before reading the book was that he wasn't even using penetration figures from the water testing, he's only using the expanded bullet diameter created by firing into water.

This is not correct. The model also uses the mass of the bullet and its impact velocity to calculate penetration and permanent cavity mass. It's right there in the equations, can't miss 'em- they are the variables "M" and "V" in the equations.

Not at all. I can't see that he's making any claims that are false.There are one of two options. Either his model isn't very accurate, or he's using a lot more than just a few easily measured parameters to make it work.

In one breath you say that you can see no claims that he (Schwartz) is making to be false and then you follow it immediately with two options that assert that either his model is not very accurate or that he is being less than truthful about the construction of his model, even though in the book he clearly displays the derivation of the model and has it laid out plainly for all to see on pages 16-20*. I am pretty sure that you can't have it both ways.

Holy "double-talk", Batman!

He says that all you need to use it is the bullet's expanded diameter, velocity, and recovered diameter and he explains it all in the book. So now he's either a fool or a liar?

In all fairness, there's a third option that you've failed to mention- his model may be an accurate representation (r = 0.94, n = 700+) and he has been truthful about the parameters needed to make it work.

Would you also be so bold as to call Duncan MacPherson (his model has an n = 400+) a liar or a fool, given that he and Schwartz have both produced such models?

With all due respect, I could not help but notice that you'd managed to completely "side-step" answering these questions in your latest response.

Is it your position that the author is a liar and/or a fool or is it that he is making no false claims?



* Unfortunately, I can't post it here in its entireity since doing so would probably violate copyright law and I don't wanna get in trouble for doing something bone-headed like that.