The U.S Court of Appeals for the Fourth Circuit ruled that Maryland's ban on assault rifles is constitutional. The court found that assault rifles are weapons of war—under the precedent set by Heller v. District of Columbia, the government is explicitly allowed to regulate military style weapons.
"Put simply, we have no power to extend Second Amendment protection to the weapons of war," Judge Robert King wrote, referring to the "military-style rifles" that were also used during mass shootings in Aurora, Colorado, San Bernardino, California, and Orlando, Florida.
Gun owners say it's meaningless to call a gun a "weapon of war." People like using reliable tools—assault rifles are just another tool.
This is all part of the reason why I, a civilian, own a military-grade combat weapon. I don't want to shoot and miss; I don't want the gun to jam because it's dirty or cold; and when I'm hunting game I don't want to hit my target and then have it run off into the woods and die lost and wounded because I didn't "bring enough gun." Like my grandpa with his "military-grade" lever action rifle, I want a modern firearm that's popular (which means parts and training are cheaply and widely available), ergonomic, rugged, accurate, and reliably effective, so that none of the aforementioned bad things happen to me when I'm shooting.
The features of that make a weapon "military grade" are also features that can be switched out to make a completely different gun. At the end of the day, these guns are tools with many legitimate uses. It does not make sense to ban a class of guns simply because people are afraid of them.
So cops and civilians buy AR-15s because that one gun can be adapted to an infinite variety of sporting, hunting, and use-of-force scenarios by an amateur with a few simple tools. An AR-15 owner doesn't have to buy and maintain a separate gun for each application, nor does she need a professional gunsmith to make modifications and customizations. In this respect, the AR-15 is basically a giant Lego kit for grownups.
Proponents of banning assault rifles say their capacity to hurt and kill greatly outweigh any legitimate civilian purpose. Assault rifles were designed for military applications and are especially suited to kill other people. They cause more devastating damage to the human body compared to handguns.
These high-velocity bullets can damage flesh inches away from their path, either because they fragment or because they cause something called cavitation. When you trail your fingers through water, the water ripples and curls. When a high-velocity bullet pierces the body, human tissues ripples as well—but much more violently. The bullet from an AR-15 might miss the femoral artery in the leg, but cavitation may burst the artery anyway, causing death by blood loss. A swath of stretched and torn tissue around the wound may die. That’s why, says Rhee, a handgun wound might require only one surgery but an AR-15 bullet wound might require three to ten.