Current law strictly limits the sale of gun silencers, devices attached to or that are part of the barrel of a gun to reduce the amount of noise and visible muzzle flash. While it is legal to buy silencers in most states, a purchase requires a nine-month waiting time and a special $200 tax. The gun industry and the NRA have long complained about these restrictions under the National Firearms Act, the law that regulates machine guns, and are lobbying for legislation to make it easier to purchase them.