Silencers- aka suppressors- are regulated as firearms under thae 1934 National Firearms Act, much like a ful auto or a short barreled shotgun. We have already answered 3 threads today on Class III stuff- same things apply to suppressors. You must be 21, in a state that does not prohibit, and transfer must be through a dealer with a special license to handle those. Transfer must be approved by the BATFE. $200 tax, prints, paperwork.
See the dealer, who can explain the paperwork. If you are planning to CARRY a handgun with an installed suppressor, you might want to check the dimensions- it ain't what you see in the movies....
What we have heah is.... failure to communicate.