laws intended to keep weapons designed to kill a large number of people out of the hands of criminals and the mentally unstable.
If the laws you speak of were meant to do what you claim, then the AR-15 would be joined by the Mini-14 on the list of "evil assault weapons".
Alas, the Mini-14 is on the Exempt List of each of the Assault Weapon Bans.
Of course, the Mini-14 is exempt because it is a self-loading rifle firing 5.56mm (.223 for you non-metric types) rounds using magazines ranging from 5 to 35 rounds capacity, as opposed to the AR-15, which is a self-loading rifle firing 5.56mm (.223 for you non-metric types) rounds using magazines ranging from 5 to 35 rounds capacity....
If it isn't obvious from the above descriptions, there are two essentially identical rifles - one an evil assault weapon, the other a perfectly fine sporting rifle out there in the wild. If the various bans on things like the AR-15 lower receiver (or the AR-15 itself) were actually about keeping guns out of the hands of criminals, there would be no distinction made between the Mini-14 and AR-15.
What the Bans actually are is a ban on Scary Looking Rifles. And that's all they've ever been - a feel-good measure that accomplishes nothing....