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In a 12 Apr 2023 ABC nightly news segment on the 2023 Louisville Shooting (in which an AR-15 style rifle was used), they included a segment of a press conference with Dr Jason Smith, Chief Medical Officer of UofL Health.

Beginning at timestamp 4:30:

Rifle rounds pulverize and liquefy tissue because how fast they are moving. They powder bone. They tear large gaping holes in tissue. You don't see that with a handgun. You simply don't.

Do AR-15 rifle rounds behave this way?

Related question, since the original quote is in comparison to handgun rounds.

atk
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  • I think the caliber is relevant to the question. AR-15 platform supports multiple different calibers. ref: https://en.wikipedia.org/wiki/AR-15_style_rifle#Calibers – pinegulf Apr 14 '23 at 06:21
  • @pinegulf If it's an AR-15 you can assume it's 5.56x45 unless specified otherwise. – Schwern Apr 17 '23 at 16:33
  • [Is this Rock River Arms RUK-9BT a pistol or an AR-style weapon?](https://www.youtube.com/watch?v=Dm0MeOPkk-I) The answer is both. The shorter barrel length does lead to lower muzzle velocities compared to a rifle, but not that much lower. Moreover, there are 50 caliper "handguns". A Weaver stance would be highly recommended here so as to avoid a sprained wrist. Does that make these not handguns? Finally, an old-fashioned .22 caliper pistol bullet that enters a victim's brain will bounce around several times inside the victim's brain skull, resulting in instant & 100% complete lobotomy. – David Hammen Apr 20 '23 at 11:40

2 Answers2

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I suspect the term "pulverized" means something a little different in this context. From an animal study:

Deer were shot with a .223 caliber rifle from 10–125 m and approached immediately (<20 s) for assessment. [...]

Bone fragments have a “pulverized” appearance resulting from combined ballistic kinetic features related to velocity, mass, and surface area, and the rotational forces (or tumbling) imposed on the projectile when it impacts the target. [...] This demonstrates the explosive nature of the impact. [...] Numerous amorphous ballistic lead fragments overlie the many bones of the affected cranial cervical spine demonstrating the transfer of kinetic energy to the tissues beyond the path of the projectile and the related collateral tissue damage.

In layman's terms, a portion of the bone impacted is reduced to tiny fragments. And so is a part of the bullet for that matter.

One of the [many] radiographs from the paper is probably more explanatory than words though:

enter image description here

Fizz
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    "*I suspect the term "pulverized" means something a little different in this context.*": different to what? Your quotes appear to support the use of the term _pulverize_ the way I would understand it (converting to powder, tiny fragments), is there some other meaning? – terdon Apr 14 '23 at 11:04
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    @terdon: The original Q title had it as "liquify bodies and/pulverize bone", so they probably interpreted the effect to be more Star Trek -like, i.e. make the [whole] body go "poof" :D – Fizz Apr 14 '23 at 13:56
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    "Liquefy" may be interpreted differently by different readers as well; in some cases, "liquefaction" indicates that something temporarily behaved like a liquid (e.g., sandy surfaces in earthquakes) rather than it literally became liquid. – Cristobol Polychronopolis Apr 14 '23 at 14:20
  • @CristobolPolychronopolis exactly -- with respect to the forces involved in the shockwave from high speed bullets, flesh behaves more like a fluid than a solid. My generic layaman interpretation of "pulverize" is to crush into fine powder. This is not what bullets do, but it is, in the right context, a valid interpretation of the term. – Dave Apr 14 '23 at 15:00
  • Speaking as the OP, my interpretation is the layman's interpretation - turns things to powder and liquid. The same interpretation I expect most all the non-experts watching the news to take. – atk Apr 19 '23 at 01:21
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This quote refers to the phenomenon of temporary cavitation where the bullet's motion through the body creates a shock-wave that distorts and damages the flesh around the path of the bullet. "Penetrating Trauma Wounds Challenge EMS Providers", JEMS R. Hodnick 2012 puts it this way:

  1. Cavitation: When a high-energy projectile travels through the relatively liquid human body, it forms a cavity along the track of the bullet. In actuality, there is both a permanent and a temporary cavity formed. As a bullet moves through the tissues the energy of the bullet causes a temporary radial stretching, forming a cavity that soon closes as the energy is dissipated. However, within the central portion of the projectile path there will be enough tissue damage to cause a permanent cavity. For low-velocity weapons, such as knives, there’s little difference between the permanent and temporary cavity. As the energy of the projectile increases, however, the size of the temporary cavity increases accordingly. In essence, a considerable amount of damage is done by the formation of the temporary cavity. This is why high-velocity/high-energy weapons can cause so much more damage.

This article also references the fact that bullets, and more so higher energy bullets, can shatter (though not "powder") bones:

Connective tissues that readily absorbed kinetic energy would serve to limit tissue damage. Bones, on the other hand, readily break and fragment when contracted by a projectile.

Dave
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    At 2:00 [this video](https://youtu.be/8Yg67Ln5Eho) shows the cavitation effect of 5.56x45 on ballistic gel in slow motion. – Schwern Apr 17 '23 at 16:34
  • That sounds like poking holes, rather than pulverizing and liquifying. Can you clarify why you think the Dr Smith would have thought a temporary wound cavity would qualify as pulverizing/liquifying? – atk Apr 19 '23 at 01:22
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    It's a common "feature" of reporting on technical subjects that the specific technical terms used are words which are also used by lay people in different contexts. In this case, I believe the term "pulverize" is intended to mean what a lay person would use the word "shatter" for, and as I mentioned in a previous comment, "liquefy" probably is meant to convey "cause to temporarily behave like a liquid" rather than literally "cause to become a liquid." – Cristobol Polychronopolis Apr 19 '23 at 14:16
  • @atk I don't know how to fit this into the answer in a manner that suits this SE, but a key feature of a (ideal) fluid is that it does not support shear stress -- different parts of the fluid can slide relative to one another. This is different from a solid, where if you push on one part, it makes the whole thing move. What's going on is that the amount of shear that the tissues can support is so much smaller than the differential forces involved in the bulltet's shockwave that the tissues "behave like a fluid" -- they just slide relative to each other. – Dave Apr 19 '23 at 16:34