Given the history of Postal Workers, and their anti-gun policy, regarding shipping of firearms, I'll stick to UPS, tracking numbers, and a more "realistic" approach.
Received my Kel-Tec, couple of years ago via UPS, dealt with my Walther PPK/S recall, the same way, and my Sig 556 after a squib rd. All trips required service at the "mother ship", and had no issues.
Considering the financial status of the USPS, one would think, they would be more "open" to shipping whatever they can.