We have at least 2 retired USPS employees that I know of that are active members of the Lugerforum (& you know who you are

). To them I pose this "theoretical" shipping question and ask them to opine on this shipping strategy--so please give me your legal opinion even though you are not a firearms lawyer and don't play one on TV. Are these assumptions valid?:
1. I believe that if you ship a "firearm" via USPS you must declare that fact at the mail origination point.
2. The declared firearm package must be shipped overnight
3. I ASSUME that the postal regulations do not define what constitutes a "firearm".
4. So if #3 is true, whose definition does USPS use? Or do we further assume the intent of the regulation applies to a "complete" firearm?
5. Does a stripped, serial numbered, pistol frame, or rifle receiver, constitute a "firearm" in the eyes of the USPS? If so, what published USPS document so states that?
6. If HALF of a pistol is shipped in one package and the other HALF is sent to the same address in a separate package, have we, as a C&R license holder complied with the law AND the USPS regulations?
I believe that this situation is a legal gray area and I am not sure that I would want it "officially" defined. But the experience and opinion of our former USPS members could prove enlightening.
What I know for sure is that in my own experience, priority mail with delivery confirmation has never failed to arrive at the intended destination. And they have never been molested in route.
Ladies & Gentlemen... I open the floor for your educated guesses and expert discussion!
Thanks in advance for your contributions to the collective knowledge of the forum.