Apparently not.
Hassled would not happen. If you check a firing pin, magazine, or a short list of other parts without a firearms declaration, and happen to be discovered, you will receive a $4000 fine. "So sorry, I forgot that was in there." won't fly (forgive the pun). It is a zero tolerance policy.
Anyway, the entire point is to declare and secure your case with non-TSA locks and know it will not be opened without your presence.