The bad thing about shipping firearms, is that they have a tendency to disappear.
I have a friend here who has a local gun shop. He is active Army, and they had several pistols customized with their 101st Airborne info & unit motto on them. He had shipped them out to his guys, and 2 of them disappeared in the Atlanta airport. All they found were the empty pistol cases, with the paperwork, lock, etc... in them. Guns & mags were gone, taken by an airport employee. He had shipped them FedEx, and they were insured. Insurance company was giving him a hard time about replacing them, though.
Since it has to be listed what is in the box, everyone who handles it knows what is inside. Just the chance you take, I guess. Good luck.