Massachusetts has heavy restrictions on NFA weapons. Silencers are limited to officers of the law. There are destructive devices that are banned at the state or local level. Some counties have complete banns on DD's while other do not. While assault weapons aren't banned they require a permit that is rarely issued. SBS's, AOW's, and SBR's are legal as long as the have been approved by the ATF, and follow all assault weapon laws. This includes local assault weapon laws. are allowed with proper approval from the ATF, provided they comply with the current assault weapon law and local restrictions.
NFA weapons refer to a federal list of firearms that the government requires owners register. Not all states follow this law, and others have partial restrictions, full banns, or the need to register firearms in the NFA data base. Examples of firearms or other weaponry considered a NFA regulated weapon includes, but is not limited to: Machine guns, firearm suppressors, short barreled riffles and shot guns, and anti-tank guns (.50 caliber and up).