You can send a long gun straight to a gunsmith, and he can send it straight back to you.
This would be different with any transfer of ownership.
For instance, if your buying a long gun from an individual or gun maker or gunsmith, they must send the gun to your chosen dealer -for transfer.
The 'gun' bound by this example, is the action. It is serialized and tracked with each transfer. No other part of the gun matters at all. They are just parts.
Few in shipping understand this, and I have had best luck shipping with the good ole US Post Office. But not until teaching the Post Master how to do her job.
This is something that varies from town to town, and you might want to breeze over the requirements available at their website before walking in there with a firearm in hand.