Democratic presidential nominee Barack Obama talked about gun control and the Second Amendment during a radio interview in Philadelphia on Friday morning. Illinois Senator Barack Obama was a guest on KYW's sister station, WPHT-AM 1210. Obama told talk show host Michael Smerconish he's a firm believer in the Second Amendment right to keep and bear arms -- but admits there must be some limits: "I do believe in some gun safety measures -- so, for example, with all the shootings in Philadelphia, most recently police officers, I want to make sure that we can trace back guns and bullets that...