Rules on shipping

My great grandfather bought a Sears Long Tom shotgun in 1927. My grandfather somehow tracked it down and got it in his hands. When he died it ended up with my aunt in California and that is where it's at today.
This evening my mother was here for dinner. She got a phone call and it was my aunt. They've been scheming on getting that shotgun to me and both of them are clueless and can't be taught. Little squabble going on the legality of shipping the firearm here to Illinois.
I told my aunt to find a gun dealer with FFL and pay them to ship it because that is how it is done properly. My mom, who has never even fired a firearm steps in and tells aunt to just ship it in pieces. I'm not so sure that is the proper thing to do.
So...
Can anyone validate that what I said about using an FFL is right. I think that there is one part that's not legal to ship without an FFL. The receiver that has the serial number on it. Am I right?
This evening my mother was here for dinner. She got a phone call and it was my aunt. They've been scheming on getting that shotgun to me and both of them are clueless and can't be taught. Little squabble going on the legality of shipping the firearm here to Illinois.
I told my aunt to find a gun dealer with FFL and pay them to ship it because that is how it is done properly. My mom, who has never even fired a firearm steps in and tells aunt to just ship it in pieces. I'm not so sure that is the proper thing to do.
So...
Can anyone validate that what I said about using an FFL is right. I think that there is one part that's not legal to ship without an FFL. The receiver that has the serial number on it. Am I right?