oberkommando,
I'm pretty sure that ATF regulations require that you inform a shipper when a package contains a firearm. Here is a quote from the regs that covers that:
>>>>
Sec. 178.31 Delivery by common or contract carrier.
(a) No person shall knowingly deliver or cause to be delivered to a common or contract carrier for transportation or shipment in
interstate or foreign commerce to any person other than a licensed importer,licensed manufacturer,licensed dealer,or licensed collector,any package or other container in which there is any firearm or ammunition without written notice to the carrier that such firearm or ammunition is being transported or shipped...<<<