The only sure thing banning guns would do is reduce the fraction of gun deaths due to accidents. The deaths from suicide would likely shift to the next most convenient method. I highly doubt we'd see significant reduction in homicides. I'd be curious to know the numbers on homicides committed using legally vs illegally obtained guns though. Excluding accidents, these issues run far deeper than access to guns. Banning or restricting them will only mask the symptom, not cure the root causes.