You do, however, fall in a different situation if you are a dealer in Class III weapons. I never heard my BIL talk about unannounced checks, usually they were pre-arranged and cordial. But that was in the 70's and 80's.

Interesting thing is that where I live, supposedly the head of local law enforcement has to approve purchase (or possesion) of Class III weapons and suppressors. Our police chief has stated in public forums in our community that he wouldn't approve one.