The Difference Between AR-15 and Normal Gunshot Wounds
An emergency room physician explains why "assault rifle" wounds are much harder to treat than shots from a pistol.
Heather Sher, a radiologist who has worked multiple mass shootings, points to a critical difference between incidents involving assault rifles and ordinary handguns.
As I opened the CT scan last week to read the next case, I was baffled. The history simply read “gunshot wound.” I have been a radiologist in one of the busiest trauma centers in the nation for 13 years, and have diagnosed thousands of handgun injuries to the brain, lung, liver, spleen, bowel, and other vital organs. I thought that I knew all that I needed to know about gunshot wounds, but the specific pattern of injury on my computer screen was one that I had seen only once before.
In a typical handgun injury that I diagnose almost daily, a bullet leaves a laceration through an organ like the liver. To a radiologist, it appears as a linear, thin, grey bullet track through the organ. There may be bleeding and some bullet fragments.
I was looking at a CT scan of one of the victims of the shooting at Marjory Stoneman Douglas High School, who had been brought to the trauma center during my call shift. The organ looked like an overripe melon smashed by a sledgehammer, with extensive bleeding. How could a gunshot wound have caused this much damage?
The reaction in the emergency room was the same. One of the trauma surgeons opened a young victim in the operating room, and found only shreds of the organ that had been hit by a bullet from an AR-15, a semi-automatic rifle which delivers a devastatingly lethal, high-velocity bullet to the victim. There was nothing left to repair, and utterly, devastatingly, nothing that could be done to fix the problem. The injury was fatal.
A year ago, when a gunman opened fire at the Fort Lauderdale airport with a 9mm semiautomatic handgun, hitting 11 people in 90 seconds, I was also on call. It was not until I had diagnosed the third of the six victims who were transported to the trauma center that I realized something out-of-the-ordinary must have happened. The gunshot wounds were the same low velocity handgun injuries as those I diagnose every day; only their rapid succession set them apart. And all six of the victims who arrived at the hospital that day survived.
Routine handgun injuries leave entry and exit wounds and linear tracks through the victim’s body that are roughly the size of the bullet. If the bullet does not directly hit something crucial like the heart or the aorta, and they do not bleed to death before being transported to our care at a trauma center, chances are, we can save the victim. The bullets fired by an AR-15 are different; they travel at higher velocity and are far more lethal. The damage they cause is a function of the energy they impart as they pass through the body. A typical AR-15 bullet leaves the barrel traveling almost three times faster than, and imparting more than three times the energy of, a typical 9mm bullet from a handgun. An AR-15 rifle outfitted with a magazine cartridge with 50 rounds allows many more lethal bullets to be delivered quickly without reloading.
I have seen a handful of AR-15 injuries in my career. I saw one from a man shot in the back by a SWAT team years ago. The injury along the path of the bullet from an AR-15 is vastly different from a low-velocity handgun injury. The bullet from an AR-15 passes through the body like a cigarette boat travelling at maximum speed through a tiny canal. The tissue next to the bullet is elastic—moving away from the bullet like waves of water displaced by the boat—and then returns and settles back. This process is called cavitation; it leaves the displaced tissue damaged or killed. The high-velocity bullet causes a swath of tissue damage that extends several inches from its path. It does not have to actually hit an artery to damage it and cause catastrophic bleeding. Exit wounds can be the size of an orange.
With an AR-15, the shooter does not have to be particularly accurate. The victim does not have to be unlucky. If a victim takes a direct hit to the liver from an AR-15, the damage is far graver than that of a simple handgun shot injury. Handgun injuries to the liver are generally survivable unless the bullet hits the main blood supply to the liver. An AR-15 bullet wound to the middle of the liver would cause so much bleeding that the patient would likely never make it to a trauma center to receive our care.
As a technical matter, the difference is the ammunition, not the weapon itself. But this is a powerful bit of testimony as to why banning particular tool of violence might have an outsized effect.
UPDATE (2/26): Donald Sensing has a new posting out explaining, “Why the AR-15 is a very deadly military weapon.” He lays out quite a bit of detail on the evolution of the AR-15/M-16/M4 carbine series of rifles as well as their ballistics patterns.