So called assault weapons are designed to be accurate and reliable, they are not designed to kill people any more than cars are designed for people to drive them drunk.
All products can but used against their intended purpose.
The "maximum carnage" is simply a phrase that the anti gun folks use and hope the uneducated swallow it. When confronted with such nonsense, I usually explain that those guns are less powerful than a common deer rifle and functionally they operate no different than any other semi auto gun.
"He who laughs last, laughs dead." Homer Simpson