Hi,
We never shipped any guns by USPS out of our shop--always UPS back then, long guns and handguns. And it's been even longer since I did either of my two stints with the PO, but when I was with them the last time, we got a few DCM/CMP M1 Garands thru our office. They could be shipped directly to the customer and I think that's still true. But don't quote me... Whether any handgun shipments came in I dunno.
Anyway, these long gun shipments always came Registered Mail. As I recall, that was a requirement. Even if it wasn't, that's the most secure way to move items thru the US mail--the item was signed for each time it changed hands from original shipper to final recipient, and kept under lock and key most of the time. For example, when our delivery truck showed up on the dock, and the driver had a padlocked sack with "registereds" in it, he'd signed for it when he picked it up at the processing center. Then a clerk would sign his log book that he/she had accepted it, relieving the driver of responsibility, then it was logged into our office book and headed to the safe until someone else--normally the carrier--took it, when they'd sign and log it out. This process continued until the item was finally delivered. If it was not delivered the first day out, it came back, went back into the office book and into the safe for the next day's deliveries. Lather, rinse, repeat? Whoever signed last was responsible for the item... and heaven help the person who lost one.
Might be worth talking to your PO about using this service. It's a bit more pricey than others they have, but their most secure. And don't confuse it for the less secure "Certified" mail. I, for one, would be quite hesitant to put a Python in a regular flat rate Priority box and send it off like that!
Rick C