...send it overnight as "machine parts".
My point is that you don't have to "send it as" anything.
On domestic shipments there's no need for the carrier to know what's in the box. They may need to know what's *NOT* in the box. The folks at the post office often ask if there's anything breakable, hazardous, or a few other things. But they don't ask what's in the package. It's none of their business what you're shipping. I repeat:
IT'S NONE OF THEIR BUSINESS WHAT YOU'RE SHIPPING! PERIOD!
There is nowhere to declare the contents of your package, unless you're filling out a custom's form. And in that case, you wouldn't be shipping a firearm any way. Look at the FedEx Bill of Lading. Nowhere on the B.O.L. is there a space to record what the contents of the package are.
It may well be the policy of FED/UPS that you tell them, but that's not the same as a federal requirement. There is no federal requirement to ship a firearm via air. Why would there be? What difference could it possibly make to the Feds whether or not the pistol is carried on an Airplane?
If, for some reason you believe there is a federal requirement to ship via air, then go ahead and ship air, but YOU STILL DO NOT NEED TO TELL THE CARRIER THE BOX CONTAINS A FIREARM! Doing so is just asking for the clerk to cause problems, as has already been clearly attested to in this thread.
The only possible hitch I could ever see would be if you were sending a pistol-sized package to XYZ Firearms Co. Then, if the clerk were to overstep their bounds and ask what you're shipping, *THAT's* the time to tell them it's machine parts. Or for that matter, tell them it's an expensive, custom made hammer.
-Matt