"1.4 Legal Opinions on Mailing Firearms
Postmasters are not authorized to give opinions on the legality of any shipment of rifles or shotguns. Contact the nearest office of the Bureau of Alcohol, Tobacco and Firearms for further advice. "

You left off the rest of that regulation about the ATF
Of course they aren't allowed to give opinions on ATF regulations! But they are certainly able to give postal regulations. The above regulation posted is talking about whether it is legal under ATF regulations, which of course they can't comment on.
I'm definitely NOT taking up for the P.O. I have an inquiry in now for an official ruling, which I will definetly print and keep with me.
Melvin