New Haven firefighters are battling a 2nd alarm fire at the former Winchester Building on the corner of Mansfield and Munson streets Sunday evening. The call came in at around 8 p.m., and a 2nd alarm was called about 25 minutes later, officials said. The building is vacant. The Winchester Building is a four-story building where rifles used to be manufactured. It was closed down by the U.S. Repeating Arms. Co. in March 2006. The cause of the fire is not known at this time.