Actually, you probably don't know much about guns (if you did, you wouldn't ask), but AR-15s really aren't all that good at killing people.
You'll gee-haw like a donkey, because you don't know anything about guns, but it's true. The AR-15, with it's tiny .223 round (only SLIGHTLY bigger than a .22 cal varmit rifle) is not good for killing. Just too small.
When I was a kid in the 60's, my dad (huge gun lover) best friend was an officer in the Army, stationed in Viet Nam. My dad asked his friend (when he came home on leave) what the troops thought about the M16 (military version of the AR15). I'll never forget what he said, even though I was a kid:
"Actually, they aren't too thrilled with it. We have so many cases where Viet Cong are attacking us, and we'll shoot them over and over and over, and they keep coming. The guys all want to go back to the AR1 Carbine. When we shoot people with that, they go down."
I know you want to believe the liberal MYTH that so-called "assault rifles" are MAGICALLY more dangerous than other guns, but they just AREN'T.
It's just a gun. Other guns are actually more lethal. Even a .22 cal varmit gun will kill. For that matter, so will a machete or a bow and arrow.