There a multiple reasons why there is high gun violence in Chicago. It would be nice to say that gun laws within the city limits can fix everything, but it's not that easy. As someone else said, there are so many guns around, it is easy to get guns.
unfortunately a lot of gangs which used to have defined borders often due to where the projects were, when those projects were torn down are having border wars, been going on for years and so the crime has gotten worse. When I lived in Chicago many years ago sure it's a tough town, but mainly you knew which neighborhoods were OK and which ones to avoid. Another issue is that Chicago cops got slapped for being too aggressive and so there is a rumor that they are not trying so hard, especially in some areas, aka doing the bare minimum. Who knows.