You have to use someone, on both ends of the transaction, who holds a Federal Firearms License (FFL).
You should be fine on the Bethesda end:
https://www.google.com/search?q=ffl+in+bethesda&ie=utf-8&oe=utf-8
The FFL's on the shipping end will insist on seeing the weapons before they box and ship. It will be a bit of a pain for the folks in Dallas.
That is just the way it is
Anything cool from a family connection or just the gun itself?