Assault weapons were banned from 1994 to 2004. The law expired in 2004 and in 2005 the legislation (Protection of Lawful Commerce in Arms Act 15 USC §§ 7901-7903) prohibits civil Congress passed the single most underhanded piece of legislation in modern times.  In short, the legislation (Protection of Lawful Commerce in Arms Act 15 USC §§ 7901-7903) prohibits civil suits against gun manufacturers, distributors and sellers.  

It is this legislation more than anything else that is responsible for the increase in the number of assault weapons manufactured annually in the United States.  In 2004 prior to the passage of the PLCAA 100,000 assault weapons were manufactured.  In 2013 two million such weapons were manufactured. Between 2010 to 2019 the annual average of assault weapons manufactured in the United States was 8.57 million. Gun manufacturers can now flood the market with these weapons without fear of being sued.  This is because they are shielded from civil liability.  Advances in product safety have always been preceded by lawsuits.  It is the fear of being sued that drives change.