This article by Heather Sher, a radiologist at the hospital where the Parkland victims were treated, is instructive and worth every word.
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 difference is velocity; and that difference is consistent across the assault weapon spectrum.
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.
It does no good to ban weapons by name. What’s needed is legislation to ban weapons by exit velocity of the bullet, as well as magazine limits that would slow a shooter down. If our putative good guy with a gun has a 9mm handgun, he can kill the bad guy just as efficiently if he’s an excellent shot, or wound him sufficiently. In fact, let’s turn that argument on its head: If our good guy is a decent shot, he doesn’t NEED an assault weapon.
Someone should ask Dana Loesch of the NRA why the good guy has to have an assault weapon, and why a handgun couldn’t do the job. In the meantime, perhaps she should have a little look at the CT scan Heather Sher describes in her article.