You can pay the $200 to register it as an AOW I thought. Once it is registered, you can transfer it for $5 like every other AOW. Might be cheaper to just buy one new and pay the $5 stamp and wait the extra months to get the papers back.
I'd think that with the desk this wouldn't fall under the NFA law because the desk is a pretty fixed object. For example, you can make a silencer without getting a stamp if it is secured in one spot. An example would be if you made a large box and bolted it to the floor to test shooting different guns through it or something. Think of a kind of permanent shooting bench or something. I don't know the details of this though, so please no one go out and do either without checking first.
