Under the 1934 National Firearms Act, silencers are treated similarly to machine guns and explosives. The waiting time to purchase one is far longer than for handguns or other weapons — as much as nine months or more — and buyers have to submit fingerprints and a photograph. Federal law enforcement agencies keep a record of silencer purchases. There is also a $200 transfer tax on silencers. Duncan’s proposal would eliminate those requirements, as well as refund the transfer tax to anyone who has purchased a silencer since October 2015.