Guns: The mayor of what is at once America's most gun-controlled city and its murder capital wants an assault weapons ban like the one he pushed in 1994. Except it didn't work then, and it won't work now. Nathaniel T. Jackson, 40, an alleged gang member with a long arrest record, was gunned down last week outside a store in Chicago's Austin neighborhood, becoming the Windy City's 500th murder victim in 2012. Up to 80% of Chicago's murders and shootings are gang-related, according to police. By one estimate, the city has almost 70,000 gang members. A police audit last spring...