A customer of ours recently had Remington send him a replacement rifle--it had to come thru our shop. I think what others have said is correct--individuals can ship via FedEx or UPS to an FFL, but only FFL holders can mail guns thru USPS.If you own them, can't you ship them to yourself and forgo the FFL? In the same manner if a gun had been sent off to repair, you own it.... so it can be shipped directly to you.
https://www.atf.gov/file/61721/download
#6