we all know criminals of all background: felons, gang members, rapists, mentally ill, etc WILL NOT turn in their guns.
law abiding Americans WILL be at the mercy of their attackers much like our UK counterparts which have a much higher violent crime rate due to the victims being unable to defend themselves. no citizen can afford to wait for police to arrive to a scene.
background and psychological tests are fine for a potential gun buyer as a law abiding citizen has nothing to hide! those two rules can weed out the mentally ill and felons.
more importantly our Second Amendment's main use is to defend against the will of a totalitarian, communist, dictator type of government.
lastly, we all KNOW that real "assault rifles" are FULL AUTO!
the look alikes sold in stores are SINGLE SHOT!