What is a gun supressor? Is it a silencer? Is it legal in the USA?
Yes, a gun suppressor is a silencer.
They are legal in I believe 35/50 states in the US, so it entirely depends on your firearm and your state.
Machine guns/Silencers are serial numbered and registered with ATF. Maryland residents(me) can own and use these firearms and silencers as we would any other firearm. You must meet the following criteria:
* Be a US citizen
* Be at least 21
* Have never been convicted of a felony offense.
There is a procedure called a Transfer. You are require by law to pay a $200 transfer tax per silencer. This is a one time tax. You are NOT required to pay $200 annually. First, after purchasing the item, the gun shop fills out the necessary forms. They give you a packet with the Form 4 and Finger Print Cards. You then will make a trip to your State Police or other municipality.
There they will walk you through the procedure. After the authorities return it to you, you need to bring it back to the gun store. They then submit the application, finger print cards, passport photos, and a check from you for the $200 transfer tax. This process takes 30-90 days.