I know FedEx Ground requires the signature add-on for any firearm shipment. cant speak to UPS.
You're assuming the contents were declared as a firearm. This only happens if shipping from a counter like mere mortals and if the shipper chooses to declare it. Commercial customers simply affix a shipping label and turn it over to the driver and don't go through the step of declaring it. UPS and Federal Express couldn't give a damn one way or another on a commercial account.
Makes sense ... my only experience is with declaring and shipping from the counter to an FFL.
