Why are automatic weapons illegal in the US?
Automatic weapons as we usually think of them are really
semi-automatic.
That is, you fire one bullet for each trigger pull, and the
weapon charges itself with a new bullet automatically. These are
not assault weapons, though most politicians think they are.
Real automatic weapons will 'spray' out a stream of bullets as
long as the trigger is kept pulled. These ARE considered assault
weapons.
They were outlawed largely because of their use by gangsters who
had more firepower with them than the police did. Automatic weapons
are pretty dangerous because of all the firepower they emit. The
killings that you read about where "Assault" weapons have been
used, have NOT used assault weapons, only semi-automatic
weapons.