Stats & studies; Sen Feinstein(D-CA)....
Sen Feinstein's press release/website lists a few research reports & stats about the 1994 Clinton Era crime bill.
I'd answer most anti-gun supporters with the basic facts that violent crime has gone DOWN overall & even though firearms across the US are sold in record #s, less violent crimes occur with armed citizens(lawful gun owners) & license holders.
As most US law enforcement officials know(but avoid telling the public or media), most gun deaths/homicides are; " red on red" or a criminal(bad guy) murdering another criminal(bad guy).
LE should spend more time & effort to enforce the gun laws already out there. Wayne LaPierre makes this point on the main NRA website(stand your ground article).
Cops & prosecutors should go after the real bad guys(terrorists, gang members, sex offenders, illegal aliens in violent crime, etc).