A federal judge in Boston sentenced a member of the Hells Angels motorcycle gang with a long criminal record to 21 years in prison for possession of a firearm and ammunition after committing a felony, prosecutors said. Eric Franco, 38, was sergeant at arms for the Hells Angels chapter in Lynn, said a statement from US Attorney Carmen M. Ortiz. He was convicted in September and was sentenced Tuesday in US District Court in Boston. In May, Lynn police arrested Franco after finding a gun and ammunition in his apartment while investigating a report that Franco had assaulted his girlfriend, the statement said.Todd Feathers can be reached at email@example.com. Follow him on Twitter at @ToddFeathers.