The Atlantic published an account from a Parkland radiologist who interpreted a CT Scan of one victim. The radiologist has the best intentions, and we respect her efforts. However, The Atlantic fails her by not balancing her experiences with other data. The Atlantic also fails readers by not balancing the writer's experiences with other sources. On the whole, the article, to anyone with peripheral knowledge of ballistics, gets most everything wrong and bypasses major holes in the analysis.
The radiologist references speed, mistakenly in Miles Per Hour (MPH), and identifies velocity of "AR-15" bullets as the greatest factor for effectiveness in killing. She means to reference caliber .223/5.56mm. "AR" furthermore is not a type of rifle, but a manufacturer called ArmaLite. ArmaLite produced pre-M16 models going back to the 1950s. These rifles, in basic mechanics and parts, have changed little since then. The 5.56 was designed to wound up to 500 yards, and at those distances it barely kills rabbits, but at close range it is as effective as handgun rounds designed specifically for 10-50 yards.
Speed, by itself, is misleading until you factor the size and weight of the round, plus the penetration and wound cavity. External ballistics of munitions at the handgun and rifle level are measured in feet per second (FPS). And the data for rounds is velocity and energy -- which translates to 'stopping power' once you introduce how rounds behave in human tissue at certain distances.
For example, and this is to compare handgun to rifle at close range, there is immediate muzzle velocity of roughly 3000 FPS, then 2300 at 200 yards. That's the .223/5.56 used in AR-15s. That is very fast because the round is designed to travel and wound up to 500 yards. The muzzle energy is 1357. Weight is measured in grains, and .223 is about 60 grains. A .45 caliber travels more slowly with less energy, but is much heavier at about 200 grains. Compare to the 9mm handgun round at 1150 FPS and weighing 115 grains, or the .44 magnum at 1400 FPS and 180 grains.
For the .45ACP handgun round, the average FPS is about 1000 and energy 400-450. We will see that 3000 FPS versus 1000 FPS in close quarters is not the distinguishing factor for devastation.
There are very significant differences in how the round behaves once in tissue, depending on whether it fragments. And the FBI has rated the lethality of ammunition to two factors: size of terminal cavity (temporary and permanent cavity), or cavity produced in tissue behind the round, and penetration in inches into the body. These two factors are considered separately from direct brain/heart hits. You can be killed instantly by a small .22 to the brain or heart with the right penetration.
For the rifle round at close range, the brutality of reacting in the body depends on the angle and rotation. This is called the yaw factor, and rifle rounds at close range (Close Quarter Combat) have a wide variety. Could pass straight through, or twist and turn and create havoc. There is also the factor of when yaw begins in penetrating. 7 or more inches and it'll start damage very late. Same with handgun rounds at close range.
The conclusions in ballistics tests show that the .223/5.56 rifle round (AR-15) and 9mm (handgun) both penetrate roughly 30 centimeters. Why are these the same? Well, the key is momentum. The heavier bullets retain momentum at slower feet per second. They penetrate as well as higher velocity bullets like the rifle rounds. In fact, handgun rounds in schools would penetrate drywall and be more lethal than rifle rounds because of the weights.
Handgun rounds that expand, fragment, or twist are also as devastating as any smaller caliber rifle round traveling at higher speeds. Hollow point munitions not only expand to create a larger permanent cavity, but small pieces of metal fragment and split off in different directions. Rifle rounds usually remain intact and bend, twist, and yaw, but don't fragment at close range. Compare .223 to the Radically Invasive Projectile (RIP) by G2 Research.
So the takeaways for how devastating or brutal a bullet can be is 1) permanent cavity, and 2) penetration in tissue to reach organs. In schools and homes, we're dealing with the same penetration of about 12 inches. A 9mm, .40, or .45 hitting the liver will kill as effectively as the .223/5/56 in CQC. The cavity depends on angle, yaw, diameter of round, and whether we have fragmentation. Ultimately, a 9mm handgun round leaves a sufficient cavity and penetrates as effectively as a .223 AR-15 short range, despite destruction of organs as a result of yaw and fragmentation (exit wound could be a few millimeters straight through, or "size of an orange" with significant yaw after about 8 inches). The particular degree of organ destruction is an afterthought. It is destroyed notwithstanding velocity. The major factors are weight and size that result in cavity and penetration, so we get less effective handgun bullets and more effective rifle bullets at long range. That's how they are designed.
She also admits that she has seen few .223 rifle wounds and instead treated multiple handgun caliber wounds on surviving victims. Well, over time, in a representative sample, we'd likely see the same mortality rate for both types of wounds at close range. But since less than 2% of gun crimes come from rifles, we don't have a large enough sample.
We have to account for variety of wounds from varying terminal ballistics based on angle, fragmentation, and yaw. She probably saw a particularly messy liver wound from a rotated bullet. Did it enter from the back, front, or side? At what angle? The single case should not influence judgment about the type of rifle that fires that round.
To thoroughly investigate how 'devastating' a bullet can be, The Atlantic should have consulted law enforcement who do ballistic gel tests, such as at the FBI Academy. Those tests more accurately depict the overall effectiveness. They could also consult firearms manufacturers and ammunition manufacturers who test ballistics on all their products, internal and external. You would then get the full picture. Otherwise, this is a nice feature story about one CT scan, but it is not even an average or decent evaluation of the .223 round, which is what it sets out to do from the mistaken perspective on velocity.