There are over 400 million privately owned guns in the United States.
http://gunwatch.blogspot.com.au/2018/02/trump-era-nics-gun-checks-2018-starts.html
Im doing my best to run that count up some more.
The vast majority of mass killings are committed by democrats. The vast majority of inner city gang killings, (Chicago, Baltimore, St Louis etc.) are committed by democrats and far left wing ideologues.
The reason for this is quite evident. The far left promulgates and encourages hate and division. Many of low intelligence and or left wing ideologues buy into this hate and commit acts of mass violence. It is really that simple.
The problem is not guns. The problems is left wing hatred that causes these acts of mass violence.
There can be only one response to the will to power driven sociopaths who want to disarm us: NO. BFYTW. Your move.
Lets not forget the worst mass murder in an American school was NOT done with a gun.
https://en.wikipedia.org/wiki/Bath_School_disaster
FWIW so can double-action revolvers.