Mayor Michael R. Bloomberg took a rare, veiled swipe at his predecessor yesterday, challenging Rudolph W. Giuliani’s assertion that a lawsuit Mr. Giuliani filed as mayor against gun manufacturers had changed so much that he may no longer support it. Saying that the case had “not changed at all” since its inception, Mr. Bloomberg told reporters at a news conference at City Hall, “We believe that it’s a good case, and we hope to win it.” Last week, Mr. Giuliani, a Republican candidate for president, told the National Rifle Association that the suit had “taken several turns and several twists...