BANGOR — A Franklin County man has been sentenced to nearly 3½ years in federal prison for having three sawed-off shotguns that authorities said were not registered to him.

Federal prosecutors say 66-year-old Joseph Smith of Township 6 was also sentenced on Tuesday in federal court in Bangor to three years of probation.

He had pleaded guilty to charges in December.

According to court records, three shotguns with barrel lengths of less than 18 inches were discovered at Smith’s camp in September 2010 during the execution of a search warrant. The weapons were not registered to Smith in the National Firearms Registration and Transfer Record.

The investigation was conducted jointly by the Bureau of Alcohol, Tobacco, Firearms and Explosives and the Maine Drug Enforcement Agency.