St. Louis city leaders hope that a program to give cash in exchange for guns Saturday will help curb the city’s increasing violence. But experts say gun buybacks — while popular — are ineffective. That doesn’t sway the St. Louis mayor. “Frankly, if we get one, or two, or 10 guns off the street that would have been used in a serious crime, I will consider that a success,” Mayor Lyda Krewson told the St. Louis Post-Dispatch. “There is not one thing that we can do that will solve this. We have to do a lot of different things on...