Register a SA Forums Account here!
JOINING THE SA FORUMS WILL REMOVE THIS BIG AD, THE ANNOYING UNDERLINED ADS, AND STUPID INTERSTITIAL ADS!!!

You can: log in, read the tech support FAQ, or request your lost password. This dumb message (and those ads) will appear on every screen until you register! Get rid of this crap by registering your own SA Forums Account and joining roughly 150,000 Goons, for the one-time price of $9.95! We charge money because it costs us money per month for bills, and since we don't believe in showing ads to our users, we try to make the money back through forum registrations.
 
  • Locked thread
Fang
Jul 9, 2001
If you don't think ponderous, clumsy sentence structure loaded with hamfisted thesaurus wankery makes good writing, you're probably just too dumb to read my posts.

/r/iamverysmart

"Terminal ballistics" is the term used to describe the kinetic behavior of a projectile at and/or within the terminal point of its trajectory, hence the name. (Interior ballistics deals with a projectile's behavior within its launching mechanism and exterior ballistics characterizes its flight.) With respect to firearms, terminal ballistics generally concerns the destructive capabilities of a bullet, whether in an animate or inanimate object. (The ability to study bullet effects on both living and nonliving things is but one of the reasons that terminal ballistics, as a science, has supplanted killology in academic circles.)

When compared with the other fields of ballistics, terminal ballistics remains an incredibly rudimentary science. Interior ballistics is largely a solved problem whose parameters are precisely described by thermochemistry, metallurgy, and the mechanics of dynamic systems. Although interior ballistics involves a huge number of factors interacting in complex ways, we know how to produce accurate firearms that don't randomly decompose into supersonic shards of red-hot metal. Exterior ballistics also involves a great deal of randomness, all unavoidable due to the crippling handicap of having to shoot through air; however, the physics to describe projectile trajectory are all known and verified. It's another solved problem whose only remaining challenges are issues of execution.

Compared to its interior and exterior brethren, though, the science of terminal ballistics is still emerging from the sordid mists of superstition and voodoo--but with good reason. The effects of a bullet on its target is irrelevant if it misses, and the ability to ensure a bullet reaches its target is severely impaired if the launching platform is crude or currently scattered about the landscape along with bits of its wielder. Thus, the scientific refinement of ballistics follows the same path from chamber to target that the bullet takes.

But with the mastery of reliable, accurate firearms (jabs at certain makes and models notwithstanding), increasing attention has been focused on maximizing the destructive power of the projectile itself.


Wounding Mechanisms

Before you can maximize the damage of a bullet, though, one has to know why it causes damage. The intuitive answer is that bullets damange things by virtue of hitting them really fast and creating holes in the target. A premise this simple and obviously true is hard to argue with, which is why for hundreds of years advancements in terminal ballistics involved using wider bullets so that more of the target was smashed, and making those bullets heavy and fast so that the bullet would go all the way through, taking as much of the hapless target with it as possible.

But it's hard to make a science out of anything involving the phrase "puttin' holes in things." Substituting the more sterile phrase "tissue disruption" opens up new avenues of exploration beyond simply making the bullet bigger. This was already becoming obvious during the Civil War, where soldiers noticed the tendency of Minie balls to trade terminal ballistics for exterior ballistics compared to the older round musket balls. Spitzer bullets and smokeless powder produced another advancement in exterior ballistics that revealed another wounding mechanism: the shockwave caused by the sudden change in velocity experienced by a projectile encountering a viscous medium. From this awareness of hydraulic forces and high-velocity projectiles came investigation into expanding and fragmenting bullets.

At the root of all these refinements, though, is the same old goal: make big holes in things. We've just gotten better at making bigger holes with smaller bullets, or while working around limitations imposed by exterior or interior ballistic requirements.




Measuring Terminal Ballistics

The reason we have better bullets comes from increased understanding of the physics involved with bringing projectiles to a sudden and unpleasant halt. Having standardized and repeatable methods of observing the result of a bullet upon striking a flesh-like medium (ballistic gel) doesn't hurt, either.


Permanent Cavity

What we can say for certain is that when a bullet strikes ballistic gel, it leaves a permanent hole in it. The size and shape of the hole is dependent on three interconnected factors: bullet diameter, bullet shape, and velocity.

Diameter as a factor is easy: wider bullet, wider hole. However, the shape contributes. Bullets with rounded ogives are famous for pushing tissue aside and letting it reform behind the bullet. Flat-nosed bullets eliminate this problem by crushing and cutting, and bullets that change their shape by expanding or fragmenting take it a step further.


Expansion and fragmentation rely on bullet speed to work, but velocity has effects all its own. A bullet that slows suddenly in a viscous medium will often lose stabilization and tumble, enlarging the permanent cavity by traveling part of its path sideways. Above a certain speed (around 1,600 feet per second), the shock of the bullet's rapid deceleration is intense enough to exceed tissue elasticity, and the shock wave itself contributes to the permanent cavity by causing tears in the surrounding tissue.

The permanent cavity method of measuring terminal ballistics receives a lot of attention because it's measurable, repeatable, and provably useful; i.e. if the permanent cavity passes through something important, that important bit will be destroyed. Combine this with worst-case-scenario planning (expect the minimal possible reaction to a bullet strike in a given area) and you can make a safe estimate of the terminal effects of a given shot.



Temporary Cavity

One theorized incapacitation mechanism hinges on the portion of a bullet's shock wave that isn't powerful enough to completely destroy tissue, but instead just displaces it momentarily, like a powerful internal punch.

It's highly likely the forces that create the temporary cavity have some effect, but there are some problems with the theory; the largest of these is that it's not scientific. There's no reason the force of temporary cavitation couldn't be measured in gelatine, but even if that force were to be quantified, its effect in any given organism would remain unpredictable.

Therefore, the temporary cavity remains one of the vestigial remnants of ballistics' murky and superstitious past, useful only for breaking ties in a terminal ballistics debate that has long since abandoned pretenses of objectivity.


Hydrostatic Shock

Also known as "hydrokinetic trauma" and "hydraulic shock," hydrostatic shock is here used to refer to the theory that pressure waves from a decelerating bullet can be transmitted by major blood vessels to the brain or remotely to the spine, causing capacitation from neurological effects. Whether or not this happens (and if so, the effects) is a matter of some debate and suffers from the same problem that the temporary cavity theory does: It's hard to predict the effects. Additionally, it's tough to test scientifically, let alone ethically.


Exterior Ballistics Approximations

If all else fails, you can apply one number to an almost entirely unrelated problem. When applied to terminal ballistics, this principle sees cartridge effectiveness being judged by its kinetic energy, momentum, or even synthetic formulae designed to coerce measurable values into a single number that agrees with its inventor's subjective impressions of terminal ballistics. (n.b. Taylor knock-out factor)

To be fair, kinetic energy is not that horrible a means of comparing very similar projectiles: Kinetic energy is linearly proportional to the amount of force produced by viscous drag, and the amount of force exerted on the bullet is, per Newton, echoed on the surrounding
media. Kinetic energy as a measure of terminal ballistics falls apart when applied to different projectiles that react to the drag force differently or direct their force across different areas, or whose design is different, or which are stabilized differently, or any of a thousand other factors. If followed to its (il)logical conclusion, using kinetic energy as a measure of terminal ballistics would lead one to conclude that a batter who gets walked by a missed pitch sustains exactly one fourth the damage of one who gets shot by a .45 ACP hollowpoint. (Take your base!)

Using kinetic energy to approximate terminal effectiveness of a projectile is most useful for projectiles whose wounding mechanisms are based on hydraulic disruption of tissue; i.e. rifle rounds. Discounting handgun catrtridges and others which wound via direct tissue disruption avoids the ridiculous kinetic energy based situations cited above. Even in the realm of rifle rounds, though, kinetic energy doesn't tell the entire story. Bullets designed to fragment may produce terminal effects beyond those anticipated by kinetic energy alone. 5.56x45mm is a good example of this phenomenon.

The other numbers used to attempt to coerce the complexities of terminal ballistics into a single number have much less justification. The appeal of single-number approximations of terminal ballistics comes from the fact that they're easy to compare and support black-and-white conclusions. Unfortunately, the complexities of terminal ballistics cannot be condensed down to a single number representing "damage."


Fallacies and Misconceptions

Knock-Down Power

This one hardly requires explanation, as most right-thinking homonids have long since been convinced that the momentum of a bullet is insufficient to physically force anything but the smallest organism to fall over. For further reference, refer to the Laws of Physics (Isaac Newton, Editor), specifically momentum and how it governs inelastic collisions.


One-Shot Stop

Marshall and Sanow's examination of a large number of police shootings produced their infamous statistical analysis of the percentage of times that a single shot to the torso from a given caliber caused the individual being shot to cease hostilities. Even though this study is grossly unscientific (and here's why), it still gets cited because it has the appeal of simplicity that, as mentioned above, leads people to use exterior ballistics numbers to draw conclusions about terminal ballistics.


Ballistic Gel

Ballistic gelatin is useful as a scientific means of comparing the performance of various projectiles in a medium designed to simulate the density of human muscle tissue. In this it excels and represents one of the factors that helped drag terminal ballistics kicking and screaming out of the realm of supersition and subjectivity.

Because it's so gosh darn scientific, ballistic gel deserves to be treated scientifically, and that means not reading more into it than it actually represents. Gel testing's primary value is as a relative measurement of bullet performance. A bullet that penetrates deeper than another in ballistic gel will probably also penetrate deeper in an animal. A hollowpoint that expands more reliably in gel will probably expand more reliably in a living organism with density roughly the same as the gel.

Outside of extreme cases, though, drawing quantitative conclusions from gel tests is scientifically and logically incorrect. An example would be taking a bullet that consistently passes through two feet of gel and concluding that it is guaranteed to go clean through a human being from nearly any angle. The gel says so, but it's not necessarily the case because human beings are internally heterogenous and full of bones. Random stuff happens. Unpredictable results can always occur. Ballistic gelatine can't predict the results of shots through bones or organs because simulating that in a repeatable manner would be nearly impossible.

Ballistic gelatine sacrifices realism for consistency. Ironically, this makes it more useful than if the opposite tack had been taken. All that usefulness is itself useless, though, if people draw unjustified conclusions from an otherwise scientific measurement.


Conclusion

There isn't much of a conclusion to be drawn, especially where this subject is concerned. People continue to argue about terminal ballistics with the fervor of a religious debate because much of what we want to know remains a matter of faith. As proof, note the contentious debates that will certainly follow this post.

Also, this is a fairly incomplete writeup. I didn't touch on the history of modern terminal ballistics, neurological and psychological effects, why fast bullets shoot through metal better than slow ones, or any of a hundred other subjects capable of producing angry debates full of pseudophysics. For this content, please refer to any random gun forum.

If there are any conclusions to be drawn from terminal ballistics, these are they:

  1. Shooting things with guns is bad for them.
  2. All things being equal, bigger and faster bullets are worse for things.
  3. All things are not equal.

Adbot
ADBOT LOVES YOU

Sixgun Strumpet
Feb 16, 2009

Heh, yeah, 'round here I call myself The Enabler. I suspect pretty much everyone wishes they could be me -- I'm kind of a big deal, you see.


.40 S&W is dumb

Propagandalf
Dec 6, 2008

itchy itchy itchy itchy

Wait, you mean my BS of Killology from NRAU is worthless? loving guidance counselors.

right arm
Oct 29, 2011



Fang posted:

If there are any conclusions to be drawn from terminal ballistics, these are they:

  1. 10mm is the best pistol round ever invented.

Tubgirl Cosplay
Jan 10, 2011

by Ion Helmet


I feel like much hay has been made of caliber wars, but this sort of tunnel-vision on one dimension seems to exclude lots of important and measurable factors such as do bullets hit harder when you paint a scary face on them

woke wedding drone
Jun 1, 2003

by exmarx


Fun Shoe

Tubgirl Cosplay posted:

I feel like much hay has been made of caliber wars, but this sort of tunnel-vision on one dimension seems to exclude lots of important and measurable factors such as do bullets hit harder when you paint a scary face on them



Fang posted:

If there are any conclusions to be drawn from terminal ballistics, these are they:

1. .mario is the best pistol round ever invented.

Vindolanda
Feb 13, 2012

It's just like him too, y'know?


Tubgirl Cosplay posted:

I feel like much hay has been made of caliber wars, but this sort of tunnel-vision on one dimension seems to exclude lots of important and measurable factors such as do bullets hit harder when you paint a scary face on them

They only hit hard if you call them something that combines a scary concept like "black talon", "grey python", "nuke wizard" and a technospeak thing like "MAXIMUM FRANGIBILITY", "EXPLOSIVE INTERVENTION FORMAT" or "MAGICK DETH". That last one only really goes with the grey wizard round.

Creamed Cormp
Jan 8, 2011

by LITERALLY AN ADMIN


Since I'm an idiot who needs to get stuff explained to him in two sentences or less, if I need to shoot at something, I should strive to have :

- a bullet that goes at least 12" in bare gelatin in tests
- as much expansion as possible
- controllable recoil

Did I miss anything?

Butch Cassidy
Jul 28, 2010



WitchFetish posted:

Since I'm an idiot who needs to get stuff explained to him in two sentences or less, if I need to shoot at something, I should strive to have :

- a bullet that goes at least 12" in bare gelatin in tests
- as much expansion as possible
- controllable recoil

Did I miss anything?

The F.B.I. looks for at least 12" in denim-covered gelatin. And it is worth noting that they chose 12" because bone testing is not consistent enough to mean poo poo, so extra penetration in gel should mean that the bullet will make it through a bone or two and still reach vitals. And the denim likes to clog hollow point cavities and prevent expansion to give a "worst-case" expansion/failure to.

But, as it it the best only slightly half-assed standard we have right now, you want a round that makes 12-16 inches in denim covered ballistic gel. Of the available loads that do that, you want, in order:

- The one that shoots most to your sights (J-frames call your office.)

- Cheapest

- Ends with the largest and most consistent expanded diameter

- Lightest recoiling

- Special note that low-flash powders are currently snake oil and there has been zero authentication that reduced flash from a handgun realistically affects your eyes, let alone influences a civilian or police gunfight.

The Eyes Have It
Feb 9, 2008

Third Eye Sees All
...snookums

This brings to mind an article from The Box O' Truth where it was all about shooting a car.

The conclusion was that what happens when you shoot into a car is unpredictable. Because there is so much "stuff" inside a car, the seats, etc etc it's not possible to say something like (for example) "Round X will go through a car door, Round Y will not".

Shot #1 might punch right through but shot #2 (which was only a couple inches away point-of-impact-wise) might not because #1 just punched through the siding, but #2 happened to hit some structural thing on the way and it deflected the bullet's path, or the bullet hit something solid and fragmented & instead of a bullet the other side just gets a few fragments, or any number of or combination of things.

Much like shooting in a house (or into a person), the insides are complex and unpredictable things happen. Bullet #1 hit a bone (or water pipe, etc) and shattered, but bullet #2 same caliber and hitting an inch away from #1 just punched right through because nothing was in the way.

And on top of it, the more something is shot the more it changes. A cinder block can stop a bullet pretty good but it's cracked as hell after the first shot. It's far less effective to any subsequent rounds. (Just to mix up more crap into the "what happens when you shoot X with Y" - not only is it complex to begin with, it's different the more it happens.)



That's also part of why it's important to define what you're measuring and why. Not that it matters to the people who immediately poo-poo a drywall puncturing setup pointing out that your test is invalid because your walls aren't filled with wiring or water pipes like real ones are. Of course they're not, why would you make your setup less repeatable and more random?

DJExile
Jun 27, 2007



kommieCCWapprovedlist.txt

DakianDelomast
Mar 5, 2003


Thanks Fang, I appreciate the effort post. In the interest of actually contributing to the thread I wanted to throw out some discussion points.

I think caliber selection is an obtuse exercise. After researching, I have drawn some of my own conclusions. Human beings are tough to kill/stop in the short timespan of an engagement, and pistol bullets are terrible at incapacitating someone.

As Fang stated there appears to be a 1600 ft/s that starts to create significant tissue damage beyond the immediate wound channel, but bullets fired from a pistol rarely exceed that. The only ones that start to are .357 magnums or 10mm pistols for example. The problem then becomes that the pistol bullets have such a high momentum that they commonly overpenetrate the target. Pistol rounds as designed then are primarily organ penetrators that rely on shot placement.

However rounds must penetrate reliably as well. That's where the FBI evaluations come in. Bullets must be able to penetrate a target and some of the weaker pocket gun loads fail to reliably achieve penetration as well. So the sweet spot is a bullet that reliably punches through a target, but does not have enough momentum to regularly punch through the other side.

Essentually what I'm saying is anything more powerful than 9x19mm is only increasing risk of overpenetration in pistols.

There are a couple wild cards out there and these considerations make me think that the FN 5.7 round is more viable than people give it credit for, but I'll leave that topic open for now.

Also I really like the link Kommie gave me for looking at terminal ballistics. If you're interested in reading: http://pistol-forum.com/forumdisplay.php?19-Ammunition

MohawkSatan
Dec 20, 2008

by Cyrano4747


Just out of curiosity, if 1600+ fps bullets do damage out of proportion with their size, what does that mean for 7.62x25mm? It might be a pretty small bullet, but some of the hotter loads are pushing 1800 feet per second. Would the lower weight help remover the overpenetration, or would they be too light to be effective in the first place?

Fang
Jul 9, 2001
If you don't think ponderous, clumsy sentence structure loaded with hamfisted thesaurus wankery makes good writing, you're probably just too dumb to read my posts.

/r/iamverysmart

Mister Sinewave posted:

That's also part of why it's important to define what you're measuring and why. Not that it matters to the people who immediately poo-poo a drywall puncturing setup pointing out that your test is invalid because your walls aren't filled with wiring or water pipes like real ones are. Of course they're not, why would you make your setup less repeatable and more random?

Yes, exactly! There were some objections to the last drywall thread Miso-Beno and I did because it didn't feature pipes or other intersticial features. But we chose the plain wall sections because we wanted a worst-case scenario test that was as repeatable as possible.

On a terminal ballistics note, I always found it interesting that penetration of metal is all about velocity, but penetration of softer objects is more affected by momentum. .45 ACP actually penetrates more than 9mm; it doesn't help that 9mm tends to mushroom more reliably due to the higher velocity.

gimpsuitjones
Mar 27, 2007

What are you lookin at...

Fang posted:

penetration of softer objects is more affected by momentum

and presumably sectional density

Quickshanks
Oct 3, 2011

So damned good.

https://www.youtube.com/watch?v=EaSjx9Y5FHo

This is the way it is.

Cyrano4747
Sep 25, 2006



Thanks for the write-up Fang, there are few things I like with my morning coffee more than a thoughtfully written, well-researched effort post.

Vindolanda
Feb 13, 2012

It's just like him too, y'know?


Cyrano4747 posted:

Thanks for the write-up Fang, there are few things I like with my morning coffee more than a thoughtfully written, well-researched effort post.

Is your wank bank referenced Harvard or Chicago style?

For reals though, nice effort post Fang.

Adbot
ADBOT LOVES YOU

Cyrano4747
Sep 25, 2006



.

Cyrano4747 fucked around with this message at 04:29 on Aug 13, 2014

  • Locked thread