While the statute calls these devices “silencers” or “mufflers”, the US NFA industry term is “sound suppressor”, as the word silencer has been given a negative connotation, and because it is inaccurate, as these devices do not eliminate all sound from firing a gun. However you can point the folks who get all high and mighty about the use of the word “silencer” to this definition; it is the legal term.

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The statute of limitations on violations of the NFA is three years, with the possibility of extension of that time to six years for some wilful violations. See 26 USC sec. 6531. The statute of limitations does not begin to run on possession offenses until the possession stops. As long as you possess the contraband item, you are in danger of being prosecuted.