A gel expert explains

Shawn Dodson · Nov 29, 2019

YOU asked the DUH question. YOU get the DUH answer.

Which bones should be cast in ordnance gelatin to make the results "realistic"?

Rib? Already been done - no difference.

Hand, wrist and arm?

Spinal?

Cranium?

Hip?

Leg?

Foot?

And at what depth along the wound track should these bones be placed? What angle? Should they be juvenile bones, adult bones or geriatric bones?

What information of value can we obtain that is useful to us?

In a self-defense perspective, the only performance in bone we care about is that a bullet can blast through to reach and damage vitals.

If you cast bone in gelatin to match a specific situation with a living animal the results in gelatin will mirror the results in the living animal.

Shawn Dodson · Nov 29, 2019

No they are not. Projectiles do not get deflected completely off course in homogenous ballistic gelatin.

I refer you to the article "The Wound Profile & The Human Body: Damage Pattern Correlation" by Martin L. Fackler M.D., in Wound Ballistics Review Volume 1, Number 3, pp. 12-19. The conclusion states:

The bullet penetration depth comparison, as well as the similarity in bullet deformation and yaw patterns, between human soft tissue and 10% gelatin have proven to be consistent and reliable. Every time there appeared to be an inconsistency (the German7.62 NATO bullet for example) a good reason was found and when the exact circumstances were matched, the results matched. The cases reported here comprise but a small fraction of the documented comparisons which have established 10% ordnance gelatin as a valid tissue simulant.

RetiredUSNChief · Nov 29, 2019

The problem most people have with ballistics gel is they don't understand what purpose it was designed for and how to interpret any data gathered from it.

As has been stated, it was developed to SIMULATE the relative DENSITY of soft human tissue (yeah, yeah...pigs and whatnot).

When it comes to terminal ballistics, there are so many different factors which affect it that trying to compare ANYTHING is an exercise in futility when you start looking at different bullet masses, diameters, velocities, designs, angles of penetration, clothing, bone structures, different organs, muscle/fat/organ tissue properties, etc.

So, in an effort to simplify things I rather suspect that the FBI asked themselves "What ballistic property is the most important when it comes to terminal ballistics and how can we set up an experiment to quantify that property in a repeatable way, while producing results which we can then relate to probabilities in human targets?"

And then one guy in the back of the room said "How about penetration? Seems to me that nothing else matters if you don't have a bullet which can penetrate deeply enough, and reliably enough, to reach vital organs in the first place."

The facilitator probably said "OK, that's a start. And how do we go about measuring this?"

Another guy, probably eating lunch that his wife packed for him, was sitting there poking the green jello dessert his wife packed for him, which had little bits of fruit suspended in it and said "Heeeeeeyyyyy...I've got a idea! Now, hear me out before you say anything!"

Next thing you knew, ballistics gelatin was born.

It was intended to be a way of producing repeatable and quantifiable measurements of the relative penetration characteristics of various types of ammunition. Anybody could mix it up using the same recipe, at the same temperature, and reproduce the FBI documented results. They could use all kinds of different types of bullets, from any gun they wished, tabulate the results and then compare the results. It didn't matter who did it, either...FBI in the lab or Billy Ray Joe Jim Bob in his back yard. They could say that, relative to this or that bullet, this other one will or will not penetrate as deeply.

It was NOT intended to be a way of producing such measurements as "tissue damage", "bullet deflection", "hydrostatic shock", or any of the other stuff. Because human tissue is too complex to design something like that around...and it varies too much from person to person as well. There are too many other "factors" involved. Fat or skinny person? What about body builders? How do you reliably model the layers of skin tissue, fat, organ tissues, body hydration, temperatures, etc. at all angles?

Too complicated.

The ballistics gelatin test is ONLY set up to produce repeatable, quantifiable measurements on penetration in a medium which simulates homogeneous soft human tissue.

That's it.

Zendude · Nov 29, 2019

Kleanbore said:
That was not the position of those who developed it, nor was that their objective.

I agree that the design of the gel was intended to simulate tissue as close as possible. I think it is best used in comparing different cartridges.

Walt Sherrill · Nov 29, 2019

Walt Sherrill said:
If you mean using Ballistic Gelatin as a testing medium doesn't really tell us much about how a particular round will perform in human/animal tissue, I agree. (And that's what I thought you were saying.) If you mean something else, then you'll have to explain.

Shawn Dodson said:
These results can be replicated in ordnance gelatin. Fackler showed that when the exact circumstances are replicated the results in ordnance gelatin are virtually the same.

True, they can be replicated, but we never see that done in ballistic gel testing! Nearly all of the tests we see are simply bare ballistic gelatin tests showing both penetration depth and gel disruption; many observers equate those results to likely real-world results.

If your point is that ballistic gel is the best tissue simulation for predicting bullet penetration, you're probably right – and that IS a new appreciation for me.

I cited Fackler's comments about secondary wound channel damage and related consequences because this is a discussion about Ballistic Gel! My citation of those comments were not directly related to the current phase of this discussion, but I mentioned it because it addressed another characteristic of ballistic gel: Fackler points out that tissue behaves differently than ballistic gel AFTER the bullet as passed through the tissue.

While Fackler wrote about how Ballistic Gel COULD be made to simulate tissue bullet path penetration results, he only indirectly addressed the CONSEQUENCES of the damage done to the animal or human that received such a wound. In another of his comments already cited, he downplayed the role of secondary effects on the target, citing the elasticity and resiliency of the body and it's tissues. He made the point that if the bullet didn't penetrate deeply and directly damage the central nervous system, veins, arteries or other organs, the fight could continue.

One of the TV shows, I think it was Deadliest Warrior, created very realistic human torsos for their evaluations -- simulations that included bone and organ substitutes, blood, and central nervous system components, etc. Their weapon demonstrations were impressive (and even frightening). It was obvious that those body substitutes were obviously very expensive create.

Walt Sherrill said:
Gelatin isn't resilient and does not stretch (and sometimes return to it's original position) like animal or human tissue; it also doesn't have hard bones like human or animal bodies. It was designed to be a proxy for porcine tissue, which is similar to human tissue -- muscle, ligaments, etc. Not bone or internal organs. How a round disrupts gelatin is nothing like how that same round will disrupt tissue -- especially tissue of a living animal/human

Shawn Dodson said:
Gelatin isn't resilient? So it's like a block of modeling clay, eh?

You're right! It's about as resilient as modeling clay in that it doesn't try to return to it's original position. A key definition of "resilient" is a term that describes something that is "able to recoil or spring back into shape after bending, stretching, or being compressed." Ballistic gel doesn't do that.

Ballistic gel is a bit more resilient than modeling clay, but only a bit. It's limited resilience can be felt when you press a finger against it; that said, ballistic gel is not nearly as resilient as human tissue. That said, the gel's effectiveness in resisting a bullet's forward progress, as you note, is probably quite close to what a bullet would encounter when hitting a human body (including tissue, bones, organs, etc.)

Ballistic gel, like porcine or human tissue IS more easily damaged than modeling clay, but the porcine or human tissue is attached to organs, bones, the vascular system, and connective materials including ligaments/tendons which help anchor those parts in the body and which continues to constrain tissue movement after the bullet has passed through. All of this contributes to the overall resiliency of the body's tissue, and ballistic gel (or modeling clay) doesn't.

You seem to be focused on the bullet's penetration in ballistic gel (or in a human or animal body), and not really concerned about any secondary effects of the bullet's travel. Many folks seem to assume that the amount of (sometimes massive) damage they see in ballistic gel will have a similar effect on an animal or human body and infer that if the damage is great that could mean a quick bleed-out. I think that is likely a false assumption.

I would argue that except for the bullet track/penetration depth, the disruption of the ballistic gel by a given round is an interesting but perhaps meaningless byproduct of the test.

Kleanbore · Dec 1, 2019

Walt Sherrill said:
You seem to be focused on the bullet's penetration in ballistic gel (or in a human or animal body), and not really concerned about any secondary effects of the bullet's travel.

What mighy those be?

Walt Sherrill said:
Many folks seem to assume that the amount of (sometimes massive) damage they see in ballistic gel will have a similar effect on an animal or human body and infer that if the damage is great that could mean a quick bleed-out. I think that is likely a false assumption.

Good.

Walt Sherrill said:
I would argue that except for the bullet track/penetration depth, the disruption of the ballistic gel by a given round is an interesting but perhaps meaningless byproduct of the test.

There is little argument there.

Walt Sherrill · Dec 1, 2019

Walt Sherrill said:
You seem to be focused on the bullet's penetration in ballistic gel (or in a human or animal body), and not really concerned about any secondary effects of the bullet's travel.

Kleanbore said:

What mighy those be?

Click to expand...

I think the rest of my comments above addressed the only possible secondary effect we've talked about -- which is tissue disruption causing significant bleed out. I didn't really address the effects of energy transfer, as there seems to be no data or testing results to suggest that energy transfer plays any role in stopping or slowing an attacker.

As I understood it, Shawn Dodson's argument was that what is really important is enough penetration to hit something that can quickly slow or stop the attacker -- and that is the role that Ballistic Gel tests are meant to assess. He cited Fackler's comments (who did tests with modified ballistic gel that also incorporated other materials) and there was apparently less (almost no) deflection of the bullet's path in the body than most of us assume.

In some of his other studies, Fackler noted that with high speed rounds -- like those used in military rifles -- the secondary wound channel can be substantial and cause a lot of damage and rapid blood loss, but that is not the case with most handgun rounds. In the citations Shawn gave us links to, Fackler said what slows or stops the attacker is hitting something important, like major arteries, the liver, the heart, the lungs, or a critical part of the central nervous system. A thru-and- thru shot that doesn't hit any of those critical parts is not likely to quickly slow or stop an attack, and if the attacker is not stopped quickly the defender may be. A shot that isn't thru-and-thru but doesn't exit the body is no more effective (given the same caliber and bullet design) than one that does exit the body.

94045 · Dec 3, 2019

I don't have the education or credentials to really enter into this argument but I will put what I as an "Everyman" take away from.a test.

Bare Gel - Consistent Penetration over 12".

4 Layers of Denim (Or FBI Heavy Clothing) -Consistent Penetration under 18".

Not likely to under penetrate under ideal expansion conditions or over penetrate in worse case.

I don't really see the utility of gel for much more than that.

Odd Job · Dec 4, 2019

Shawn Dodson said:
I refer you to the article "The Wound Profile & The Human Body: Damage Pattern Correlation" by Martin L. Fackler M.D., in Wound Ballistics Review Volume 1, Number 3, pp. 12-19. The conclusion states:

The bullet penetration depth comparison, as well as the similarity in bullet deformation and yaw patterns, between human soft tissue and 10% gelatin have proven to be consistent and reliable. Every time there appeared to be an inconsistency (the German7.62 NATO bullet for example) a good reason was found and when the exact circumstances were matched, the results matched. The cases reported here comprise but a small fraction of the documented comparisons which have established 10% ordnance gelatin as a valid tissue simulant.

Firstly you have a typo: the article is in WBR Volume 1, Number 4.

Before we go down that rabbit hole, let me state for the record what my position is on the use of gel testing:

1) It's the closest approximation we have for a medium that equates to a narrow band of human soft tissues being struck by a bullet in controlled circumstances.
2) It has the advantage of being an ethical, reproducible test that anyone can do with not too onerous preparation requirements.
3) It is ideal for comparing two different projectiles or loadings.

I'm on board with gel testing for the reasons above, but there are trajectories and circumstances that can't be replicated in gel...or if they were (because I haven't seen it yet) the type of replication required would entail losing the benefits listed in (1) and (2) above.

pblanc said:
I have personally seen 38 Special and 9 mm projectiles deviated completely off course when they struck the fascia of the anterior abdominal wall of the investing fascia of the lateral thigh musculature. Try simulating that with ballistic gelatin.

I have also seen this kind of deflection, and more besides.

Shawn Dodson said:
These results can be replicated in ordnance gelatin. Fackler showed that when the exact circumstances are replicated the results in ordnance gelatin are virtually the same.

This is where the issue is. How do you replicate the circumstances? I am not saying we should demand this replication because I don't think it is feasible but how do you replicate in gel, a 90 degree change in trajectory when bone has not been struck?

In the article referenced above, here's what I take issue with on page 13:

Since most shots in the human body traverse various tissues, we would expect the wound profiles to vary somewhat, depending on the tissues traversed. However, the only radical departure has been found to occur when the projectile strikes bone: this predictably deforms the bullet more than soft tissue, reducing its overall penetration depth, and sometimes altering the angle of the projectile's course. Shots traversing only soft tissues in humans have shown damage patterns of remarkably close approximation to the wound profiles. (emphasis added by me)

The thing is, it isn't just bone where we see remarkable trajectory changes. I've seen a bullet do a 90 degree angle through an abdomen where no bone was struck. I went with the patient to theatre and saw the injuries for myself. That case is on LinkedIn, use this QR code so you don't have to join up or login:

https://www.linkedin.com/pulse/ptlgc-case-132-brandon-bertolli

In other cases I have seen, there has been deflection of the projectile, such that it has ended up between two tissue planes. What I suspect is going on in those cases is the bullet is encountering a tissue interface at an oblique angle in a manner that makes it susceptible to deflection. I also suspect it is more likely to happen in the second half of the trajectory where the bullet's velocity is less.

In the IWBA article, several cases are discussed where an actual wound did not match what the primary investigator was expecting, either because of impact velocity changes or because of differences between the construction of the case bullet versus the one used to construct the gel profile. I don't have any argument against that, it is obvious.
The same applies to cases where the ammunition has been recognised because it breaks into components that are recognisable radiologically.

I have also seen several cases where the retrieved projectile in a real shooting case has matched samples that I have in my collection.
I X-rayed a fellow who had an ND with a .45 Ranger SXT (marketed as Black Talon) whilst seated in a vehicle. The round went through his thigh, missing his jewels by only a narrow margin and then continued on through the seat. He had a very nasty wound but luckily no vascular injury. All he had was three or four small metallic specks on X-ray. He was patched up and sent home the same day.
The next day he came in and showed me the bullet. It was expanded like it had been fired in ballistic gel. He had recovered it under the car seat.

Here's a cropped portion of the radiograph from that case:

Then there was another case where one barb from another Ranger SXT (marketed as Black Talon) hooked on the ilium in a pelvis shot, causing a core-jacket separation. Here's the radiograph, look how the barb has been splayed back upon passing through the ilium:

It is obvious that bone makes a big difference! I can't see how that case can be replicated in gel: it might be possible, but not feasible. It would take a large number of shots with a lot of experimentation of what bone or other material to place in the path of the bullet to achieve that pattern of damage to the bullet (let alone the patient!). Just to achieve a similar bullet fragmentation pattern in gel would not be feasible in my opinion.

One area where the article is wanting is to do with penetration distances as estimated in comparisons between gel and what is seen on a radiograph. In the gel you can dissect the wound path and measure it, but on the radiographs you have some pitfalls:

1) Scale. What method have they used to make sure that photographs of profiles in gel (such as in the Croy case referenced in the article) are at the same scale as what the radiographs show? It is not an easy thing to do because the radiograph has to be taken with certain prospective controls such as having the wound profile parallel to the image receptor (in their case it would have been film since this was a few years back) and also there would have to be controls in place to work out what the magnification of the resultant radiograph was, so that the image could be manipulated or post processed to best match the gel photo. It is very difficult to do!
2) The trajectory may not be straight (even if the person was shot in the anatomical position, standing stationary).
3) The trajectory as applies to the victim may not be comparable to the radiological trajectory as plotted in the hospital. This means he was X-rayed in a different position, compared to the position he was in, when shot.

I have an example of this phenomenon, which I described in one of my cases here:

https://www.linkedin.com/pulse/ptlgc-case-120-brandon-bertolli

In that case the supine trajectory doesn't make sense because the victim was shot whilst seated and he was X-rayed supine (lying down).

Then you have projectional differences between how bullet fragments and entry and exit markers are viewed on radiographs versus the "flat" panoramic photograph of a gel block. It isn't a criticism of gel testing, it is something I point out as a difficulty when comparing the two imaging modalities for the purposes of making penetration distance and trajectory comparisons. Indeed it may well be that the actual penetration distances quoted in the article may not have been so disparate in the Croy case. Well... this could go in the favour of the gel approximations or against them. They quoted a disparity of 1" in the article. It is difficult to place any stock in that because no methods for aligning the two modalities have been mentioned.

As far as tissue interfaces are concerned, look what they say on page 16:

Rick then sent me five of the unfired bullets (identical to the two recovered from the body) and I fired them into 10% gelatin. They penetrated 25, 24, 33, 26, and 28 inches (averaging 27.2 inches) and none of the bullets deformed at all. The reason for the difference in penetration depths in the gelatin could be seen in their yaw pattern, the first two yawed early in their path and the latter three showed minimum yaw. In addition, the first two bullets passed through a rib near the end of their tissue path (probably the equivalent of a few inches of soft tissue
penetration.) The bullets in the body passed through many interfaces between one tissue and another, this usually causes more yaw than passage through a homogeneous tissue simulant. All factors considered, the gelatin and tissue penetration depths compare well. (Emphasis is mine)

Well yes, it makes a difference! it is one of the reasons why outliers in the gel profiles versus wounds from real shootings are seen.

Also...there is a certain bias in how these cases are presented in the article. The cases are selected from a pool of data where the authors purport that the profiles as seen in real life are close approximations to what is seen in gel.
If a person was to read that article they might be under the false impression that no outlying cases exist. Well they do exist, because we see them in real injuries.

That is the main point I am trying to make here. It's not that I don't put any faith in gel testing, it's that I acknowledge the limited utility of it in approximating human tissues in certain circumstances.

pblanc · Dec 7, 2019

Interesting cases.

I will mention one more real-life example in which the actual path of the projectile could not have been predicted based on the location of the entry and exit wounds, and the projectile struck only soft tissue.

Years ago, a woman presented to the hospital with a self-inflicted gun shot wound to the abdomen which was the result of a suicide attempt. She had an entry wound just above the umbilicus right in the mid-line abdomen, and an exit wound in the left upper lumbar area, about an inch and a half off the mid-line. A line drawn between them would obviously pass directly through the peritoneal cavity.

Information obtained was that she had shot herself with a 38 Special revolver that she had pressed directly into her abdomen before firing. She was complaining of considerable abdominal pain but had a stable blood pressure.

My partner took her to the OR and I scubbed in to assist. He had started out debriding the skin edges of the entry wound, then explored the wound track down to the abdominal wall muscle and fascia. It was clear that the projectile had passed through the skin and subcutaneous tissue at a slight angle to the perpendicular. There was damage to the fascia of the anterior abdominal wall and the linea alba, but we could not document a hole through it. This is not unusual however, since the fascial fibers there cross at right angles from each side, and will often close up after passage of a relatively small penetrating object. Based on these observations, we went ahead and performed a limited exploratory laparotomy of her upper peritoneal cavity.

And we found nothing. No blood, no bowel content, no visible signs of organ injury. After debriding the skin edges around the exit wound, she was observed on antibiotic treatment and did well. Over the next couple of days, she developed a band of skin ecchymosis extending laterally around her abdomen between the entry and exit wounds.

It was clear at that point what had happened. The projectile after penetrating the skin and subcutaneous tissue had struck the much denser fascial tissue of the anterior abdominal wall at a slight angle and deviated dramatically. In this case, the angle of deviation was less than 90 degrees but certainly more than 45 degrees. The projectile then continued along the path of least resistance through the subcutaneous tissue between the much denser skin and tissues of the abdominal wall, until it encountered the paraspinal muscles and their investing fascia, at which point it was again deflected at a greater than 45 degree angle to exit the skin.

Double Naught Spy · Dec 7, 2019

Shawn Dodson said:
Which bones should be cast in ordnance gelatin to make the results "realistic"?

Rib? Already been done - no difference.

Hand, wrist and arm?

Spinal?

Cranium?

Hip?

Leg?

Foot?

And at what depth along the wound track should these bones be placed? What angle? Should they be juvenile bones, adult bones or geriatric bones?

What information of value can we obtain that is useful to us?

In a self-defense perspective, the only performance in bone we care about is that a bullet can blast through to reach and damage vitals.

If you cast bone in gelatin to match a specific situation with a living animal the results in gelatin will mirror the results in the living animal.

That you don't know what bones to cast into gel or how deep further illustrates the problem gel studies. When you don't know what to do with a variable, you just leave it out and proclaim it unnecessary despite influences it may have in reality.

Hence the shortcoming of reliance on gel as the be all to end all of information on what happens inside an actual body. It falls short because it is nothing more than an idealized, best case circumstance, nothing more. Bodies have things like bones, differing tissue densities, fibers in tissues, pockets of fluid, etc. Gel is a simulant, not a replicant, and as a simulant, only simulates density and viscosity of muscle tissue, nothing else. Muscle density and viscosity are but two factors a bullet may need to negotiate going through a body. So when you ask what value the information is to us, shows that having no idea what happens when the bullet is faced with more than just the two variables, you don't know how the bullet will perform or what all other damage may or may not result.

You may only be interested in self defense aspects, but it also applies to hunting aspects.

Shawn Dodson · Dec 7, 2019

That you don't know what bones to cast into gel or how deep further illustrates the problem gel studies.

Aren't you one of the folks who complain that gelatin isn't realistic because it doesn't contain bones? I offered the question so someone like you can tell us exactly which bones should be cast in gelatin and the protocol to do it to obtain a "realistic" result that provides information of value.

Odd Job · Dec 7, 2019

I think casting bones is a dead-end: too many variables! (When it comes to the subject of this thread)

Shawn Dodson · Dec 7, 2019

Bodies have things like bones, differing tissue densities, fibers in tissues, pockets of fluid, etc. Gel is a simulant, not a replicant, and as a simulant, only simulates density and viscosity of muscle tissue, nothing else. Muscle density and viscosity are but two factors a bullet may need to negotiate going through a body. So when you ask what value the information is to us, shows that having no idea what happens when the bullet is faced with more than just the two variables, you don't know how the bullet will perform or what all other damage may or may not result.

The results depicted in ordnance gelatin, by itself, reasonably represent a simple wound involving soft tissues only.

Shawn Dodson · Dec 7, 2019

I think casting bones is a dead-end: too many variables! (When it comes to the subject of this thread)

Agreed. As I explained earlier the only performance desired with bone is for a bullet to blast through bone to reach vitals. Performance against bone is what it is.

Odd Job · Dec 7, 2019

Shawn Dodson said:
Agreed. As I explained earlier the only performance desired with bone is for a bullet to blast through bone to reach vitals. Performance against bone is what it is.

Yep!
Some crazy stuff can happen when bone is involved. This guy was very lucky, he was shot from above whilst in a seated position. Entrance wound was unremarkable:

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That's through two layers of soft clothing:

0?e=1580947200&v=beta&t=JsQ9uuYKKEGWBh2Oy7d4AnKNzGJ00A430k1sSftmN-0.jpg

0?e=1580947200&v=beta&t=t0r26YM0UwzPYC0rg-rpZAmu_eHzx9vUTNjinPp3k-s.jpg

The bullet hit the spine of the scapula and split in two! Luckily neither of the two pieces hit anything vital. Here's one radiograph:

0?e=1580947200&v=beta&t=9f9x9wVgbJM-UtAeG5ruL0Ks1596TgprobB0iI42Z_M.jpg

Here's my artist's impression of what happened:

0?e=1580947200&v=beta&t=b6kLXjDlq49IZb7sFLvrISLA0rg7MQ5O35eJ-DWX2UE.jpg

https://www.linkedin.com/pulse/ptlgc-case-106-brandon-bertolli

QED · Dec 7, 2019

pblanc said:
It was clear at that point what had happened. The projectile after penetrating the skin and subcutaneous tissue had struck the much denser fascial tissue of the anterior abdominal wall at a slight angle and deviated dramatically. In this case, the angle of deviation was less than 90 degrees but certainly more than 45 degrees. The projectile then continued along the path of least resistance through the subcutaneous tissue between the much denser skin and tissues of the abdominal wall, until it encountered the paraspinal muscles and their investing fascia, at which point it was again deflected at a greater than 45 degree angle to exit the skin.

Unlike typically in ordnance gel, it's hardly surprising that handgun bullet path in a body is often anything but close to a straight line. In a body the bullet typically traverses body structures with different densities, as well as different shear, tensile, and compressive strengths. Thus, in addition to taking "strange" paths, handgun bullet penetration in even "soft" (not bones) body tissues is often significantly less than would be in standard ordnance gel. For just one well-documented example, in a well-known shooting in Chicago several years ago it was revealed during the trial and examination of the autopsy report that the 9mm Winchester +P (RA9BA almost certainly) penetrated only 7-7.5" in 3 separate shots and the recovered projectiles looked nothing like RA9BA fired into standard ordnance gel (denim or no denim); the actual average recovered diameter was less than would be the case if fired into standard gel. The logical conclusion, then, is that the forces acting on this projectile in the body were substantially greater than the forces that would be exerted by a standard ordnance gel. RA9BA typically penetrates at least 12" in bare standard ordnance gel and probably close to 15" with four layers of denim in front of such gel.

QED · Dec 7, 2019

Shawn Dodson said:
Modeling terminal ballistic performance in fluids/liquids requires more than matching density (ρ) to achieve dynamic equivalence with soft tissue. In order to properly represent terminal performance in soft tissue, the candidate fluid/liquid must also possess the same bulk modulus (K) and internal sonic velocity (c) which are all related to one another in the Newton-LaPlace formula— c = √(K/ρ)

Compared to the respective values of c, ρ, and K in water, 10% ordnance gelatin, and human soft tissue—

H2O: c = 1,497 ms-1, ρ = 999.87 kg/m³, K = 2.24 GPa
10% ordnance gelatin: c = 1,494 ms-1, ρ = 1,040.00 kg/m³, K = 2.32 GPa
Typical values for human soft tissue: c = 1,540 ms-1, ρ = 1,020 kg/m³, K = 2.42 GPa

Not really; it's density and only density that is the highly relevant retarding factor for first several inches of expanded JHP path in a "soft solid" or water; thereafter shear/tensile/compressive forces are far more important than density in determining bullet penetration. MacPherson's work makes that quite clear. Standard gel, as well as water, of course, are reasonably good soft tissue simulants as long as inertial forces substantially predominate.

SDGlock23 · Dec 7, 2019

I don't take ballistic gel testing as anything more than a common medium in which to test bullets. I've heard it's supposed to be of a density where it simulates an "average" of flesh and bone but i don't buy that, which is why I don't put much faith in the gel testing. Another thing, one reason all major handgun service cartridges perform about the same in gel is very simple, they're designed to perform the same. However, I tend to believe that bigger bullets like .40 and .45 have less tendency (less, not zero!) to deflect off of bone because they have more momentum behind them. Despite people claiming 9mm being as good as the others because of some ballistic gel result, I know .40 and .45 hit steel plates harder and knock them over with noticeably more authority than 9mm does, which might not mean much from a strict lethality perspective, but to me that means they'll do better against bone, something gel testing does not, and cannot, account for.

QED · Dec 7, 2019

SDGlock23 said:
I don't take ballistic gel testing as anything more than a common medium in which to test bullets. I've heard it's supposed to be of a density where it simulates an "average" of flesh and bone but i don't buy that, which is why I don't put much faith in the gel testing. Another thing, one reason all major handgun service cartridges perform about the same in gel is very simple, they're designed to perform the same. However, I tend to believe that bigger bullets like .40 and .45 have less tendency (less, not zero!) to deflect off of bone because they have more momentum behind them. Despite people claiming 9mm being as good as the others because of some ballistic gel result, I know .40 and .45 hit steel plates harder and knock them over with noticeably more authority than 9mm does, which might not mean much from a strict lethality perspective, but to me that means they'll do better against bone, something gel testing does not, and cannot, account for.

Basing bullet/caliber choice on "average" conditions is sort of like building a submersible for "average" ocean depth and then expect to roam the ocean bottoms at random and not experience a big crush.

481 · Dec 8, 2019

Shawn Dodson said:
Modeling terminal ballistic performance in fluids/liquids requires more than matching density (ρ) to achieve dynamic equivalence with soft tissue. In order to properly represent terminal performance in soft tissue, the candidate fluid/liquid must also possess the same bulk modulus (K) and internal sonic velocity (c) which are all related to one another in the Newton-LaPlace formula— c = √(K/ρ)

Compared to the respective values of c, ρ, and K in water, 10% ordnance gelatin, and human soft tissue—

H2O: c = 1,497 ms-1, ρ = 999.87 kg/m³, K = 2.24 GPa
10% ordnance gelatin: c = 1,494 ms-1, ρ = 1,040.00 kg/m³, K = 2.32 GPa
Typical values for human soft tissue: c = 1,540 ms-1, ρ = 1,020 kg/m³, K = 2.42 GPa

QED said:
Not really; it's density and only density that is the highly relevant retarding factor for first several inches of expanded JHP path in a "soft solid" or water; thereafter shear/tensile/compressive forces are far more important than density in determining bullet penetration. MacPherson's work makes that quite clear. Standard gel, as well as water, of course, are reasonably good soft tissue simulants as long as inertial forces substantially predominate.

Current literature dealing with the mathematical modeling of terminal ballistic performance in tissue surrogates (e.g.: Bullet Penetration and Quantitative Ammunition Selection) supports Shawn Dodson's position on the importance of the Newton-Laplace formula in determining the suitability and validity of materials as terminal ballistic test mediums. It might be wise to familiarize yourself with the material science more thoroughly before posting more.

QED · Dec 8, 2019

481 said:
Current literature dealing with the mathematical modeling of terminal ballistic performance in tissue surrogates (e.g.: Bullet Penetration and Quantitative Ammunition Selection) supports Shawn Dodson's position on the importance of the Newton-Laplace formula in determining the suitability and validity of materials as terminal ballistic test mediums. It might be wise to familiarize yourself with the material science more thoroughly before posting more.

The referenced Newton-Laplace "formula" for expressing density as a function of sonic velocity and bulk modulus variables is irrelevant in the discussion of bullet penetration -- density is the relevant function not the variables in that "formula." Put it simply for you, definition of density is given by equation d=m/v, here density d is a function of mass and unit volume of material being penetrated by a bullet, yet neither mass nor volume of gel or muscle tissue need to be the same in order for their densities to be comparable. Got it? Besides, as mentioned in my previous post, after just a few inches of post expansion penetration, density becomes largely irrelevant and shear/tensile/compressive forces dominate bullet penetration. It's well explained in MacPherson's work and it's not rocket science; one doesn't need a degree in physics or engineering to understand it.

481 · Dec 8, 2019

The definition of density (which I am sure many THR members here are well aware of) was never disputed.

Setting that particular "straw man" argument aside for the moment—

QED said:
The referenced Newton-Laplace "formula" for expressing density as a function of sonic velocity and bulk modulus variables is irrelevant in the discussion of bullet penetration -- density is the relevant function not the variables in that "formula." Put it simply for you, definition of density is given by equation d=m/v, here density d is a function of mass and unit volume of material being penetrated by a bullet, yet neither mass nor volume of gel or muscle tissue need to be the same in order for their densities to be comparable. Got it? Besides, as mentioned in my previous post, after just a few inches of post expansion penetration, density becomes largely irrelevant and shear/tensile/compressive forces dominate bullet penetration. It's well explained in MacPherson's work and it's not rocket science; one doesn't need a degree in physics or engineering to understand it.

—you are now making the claim that Shawn Dodson has introduced information into this thread that "is irrelevant in the discussion of bullet penetration"?

QED said:
Not really; it's density and only density that is the highly relevant retarding factor for first several inches of expanded JHP path in a "soft solid" or water; thereafter shear/tensile/compressive forces are far more important than density in determining bullet penetration. MacPherson's work makes that quite clear. Standard gel, as well as water, of course, are reasonably good soft tissue simulants as long as inertial forces substantially predominate.

Shawn Dodson said:
Modeling terminal ballistic performance in fluids/liquids requires more than matching density (ρ) to achieve dynamic equivalence with soft tissue. In order to properly represent terminal performance in soft tissue, the candidate fluid/liquid must also possess the same bulk modulus (K) and internal sonic velocity (c) which are all related to one another in the Newton-LaPlace formula— c = √(K/ρ)

Compared to the respective values of c, ρ, and K in water, 10% ordnance gelatin, and human soft tissue—

H2O: c = 1,497 ms-1, ρ = 999.87 kg/m³, K = 2.24 GPa
10% ordnance gelatin: c = 1,494 ms-1, ρ = 1,040.00 kg/m³, K = 2.32 GPa
Typical values for human soft tissue: c = 1,540 ms-1, ρ = 1,020 kg/m³, K = 2.42 GPa

Shawn Dodson's CV in the field is well-known and speaks for itself. What exactly is yours?

Again, it might be wise to familiarize yourself more thoroughly with the material science before commenting further. Until then, your posts are just adding more "noise" that serve only to drown the "signal".

QED · Dec 8, 2019

I am stating a fact, based on physics (and confirmed in MacPherson's "Bullet Penetration" book that you referenced) that density not bulk modulus or sonic velocity variables expressed in the referenced "formula" are relevant in determining bullet penetration. In fact, MacPherson's bullet penetration model obviously and explicitly omits any use of bulk modulus or sonic velocity as relevant variables -- as can be easily verified by anyone just even casually perusing that book. Furthermore, on page 87 of his book, MacPherson defines all relevant variables used in his bullet penetration model -- neither sonic velocity nor bulk modulus is given as a relevant variable. It appears you have difficulty in discerning the fundamental difference between a function and independent variables of a function. Did you pick up your bullet penetration "knowledge" from your "favorite gun book" that was written by a fellow with just a degree in --- psychology?!

Odd Job · Dec 8, 2019

Let's quit the bickering. Some posts have been removed.

A gel expert explains

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