He's going to prison for collecting heavy artillery, but rapper T.I. marched in Harlem Monday with his sights aimed at stopping gun violence. The Grammy-winning artist joined the Rev. Al Sharpton at a rally honoring the memory of 13-year-old Christopher Owen and 17-year-old Cory Squires, both recently gunned down. T.I., who is set to begin a year-long federal prison stint next week for possession of illegal firearms, urged city teens not follow in his footsteps. "I... (GunPolicy.org)