Belercous- the recieving FFL has to log the gun in. With a cc of my FFL, it is easier to do. Professional courtesy. I RARELY sell, but if I do sell a gun acquired under my FFL, I need to know who I sold to (since I have to log it out) and he (if licensed) needs to log it in. So I send a cc of my FFL marked FILE COPY ONLY.
What we have here is... failure- to communicate.