http://fivethirtyeight.com/datalab/it-takes-a-lot-of-stop-and-frisks-to-find-one-gun/ describes how often the NYPD finds guns in stop-and-frisk encounters. They found guns only in about 0.1% of such encounters.
http://fivethirtyeight.com/features/where-police-have-killed-americans-in-2015/ lists incidents of killings by police with the location of the incident. Locations (census tracts) were generally poorer, more black, and less white areas.
Which means that an awful lot of people are having their 4th Amendment rights violated under the rationale that such an action reduces gun violence. I can’t see any paradigm under which the open-carry, Tea Party Libertarian would tolerate being stopped and frisked because of where they live. They would be screaming 4th Amendment to the top of their lungs. But then again, they’ve grown up with the belief that The Constitution does and should cover them. Others? Not so much.
When I was intimately familiar with Detroit crime stats - long time ago - our most common felony charge was possession of a weapon in a car. But that’s actual charges and the stops were not made to search for weapons but for other violations. I can not see value in stop & search for guns. It’s a stupid way to police in which you’re almost guaranteed - stats agree - to pick on innocent people. Bad guys don’t so much carry weapons around as have them available.