"I decided that they were just tired of my business, and went to another store. Got the same rigmarole. I finally went to a pawnshop and the owner was thrilled to hand me a signed and dated copy of his FFL to send the seller. I asked whether he was inspected by the same ATF agents as the other two stores I had visited, and he said yes of course and that the other guys didn't know what they were talking about."
This is my understanding that anyone can send a firearm to a licensed FFL or C&R to the address that is stated on the license.
If that seller sends the gun to you at your address he is liable.
The reason some do not want to deal with a C&R licensee is because it takes them time to look up that C&R license whereas the FFL one is registered and they can look it up.