Google USPS.gov, select the Offcical web site for the US Postal Service, select "All products and Services, select DMM, (Index)firearms, it will be under DMM 601.11.1, you will find everything you need to know there. I am a retired postmaster. If I send a firearm, it will only be sent registered. It is slower because each person handling it has to sign for it. It is the most secure method. The Hope diamond was sent via registered mail. All seams have to be sealed with water soluable tape, so the clerk can stamp the tape with thier red postmark stamp,( so they can prove the package has not been tampered with).
The Post Office should have the form you should be required to sign regarding the acknowledgement that gun is unloaded. It is the PS 1508. I think you can print one from the forms section of the web site.
If it is damaged you will have to prove value. But I think the USPS is just as fair as anyone out there. Sentimental value will not be considered.
