That's interesting that even in the US there must be a FFL-dealer to send or receive the gun. I always wonder how long we will have the less bureaucratic way to sell or buy licenced firearms without a dealer intermediary.
It is absolut legal in Germany to buy or sell a gun directly to a private person. Seller and buyer have to report the deal to their officials, normally the county police, in order to have the gun registered for the buyer and having the registration deleted for the seller. The buyer has to name the seller and vice versa. Even if someone in northern Germany buys a gun from a guy in Bavaria - no problem at all. No FFL-dealer required.
