The last time I flew out of DC (Washington Dulles) on a hunting trip, I was carrying a broken down auto and an O/U two-barrel set. When I was asked to open the case to have the guns inspected, the woman from TSA quickly called another younger man over. The two inspectors reminded me a a couple of dogs looking at a ringing phone as they puzzled over how many firearms I was traveling with and how they could determine if they were unloaded.
I agree with Nial that every time I have travelled with firearms that the inspection process has been a little different each time, even from the same airport. In the end there were no problems but it was a bit unnerving.
Ken