someone who has done this could hopefully chime in here
what kind of paperwork do you receive?, can you track your shipment like a regular post item?
it is quite an expensive and dangerous item, so i would think they would make the process different
I've been in this trade for almost 20 years.
Shipping firearms across state lines 101:
1. An FFL (Federal Firearms Licensee) is required somewhere in the transaction.
-In this case, if you wish to ship your firearm to another state for whatever reason, service, repair, a sale, trade, etc, YOU are in violation of the law if you do not send it to an FFL in good standing. That can be a gun shop, gunsmith, whatever. They take custody of it and log it into what's called an "A/D" book. Acquisition and Disposition log.
If it were a shop putting a new sight on it for instance, they'd log it in, do the work, and send it back to you. No sweat.
If you sold/traded it, the person who you did business with, will come in, submit a 4473 NICs background check, state/local requirement, and then go about his/her business.
You cannot legally send the item directly to someone who does not possess the license outside of your state. Within the same state is a little different and it can vary from state to state so you must do your own research to ensure you're compliant.
If you own two homes, say one in S. Dakota and another in Nebraska and you wish to ship a gun back and forth you are still supposed to go through an FFL. I know this area of the law is often ignored. I don't propose you do this as you are taking measures into your own hands. Use your own good judgement.
As for couriers/services.
UPS will ship firearms, however the company policy is that it must go to an FFL if crossing state lines. YOU will be required to show a copy of the license when at the counter. Obtaining the copy is easy enough. Contact the dealer you are going to send it to and they'll either FAX or email it to you. The physical address listed on the license is where the item must be shipped to.
Additional requirements as to the type of service you retain by UPS/FED X/ETC is up to them. Most do require an overnight requirement with handguns because they are thought of as plutonium. They don't want them in their system any longer than absolutely necessary and the chain of custody between start/finish is minimized with overnight air bills. this makes it easier for them to keep track of it.
The spirit in all of this:
Anyone who spends more than 10 minutes on Social Media will likely run into some sort of posting about gun rights and pictures of Nazi Germany. Catch phrases like "gun registration is the first step" etc...
In America, the FFL is the "registration" so to speak. When a crime is committed with a firearm, the BATF and LE go on an easter egg hunt to find out where the gun came from. They pull a serial and go to the manufacturer, the manufacturer tells who the distributor was, then the retail outlet, etc...
That is a service provided as a byproduct of having the license. It is one of the reason why we must submit to compliance audits (up to one per year) by the BATF inspectors.
Anyways, hope this helps.