Boatman- there are several different FFLs. For modern firearms, they need to be shipped TO an 01 FFL (Dealer or an 02 FFL (Pawn shop w. gun license) an 03 FFL is a collector's FFL- not valid for a modern gun.
Yes, bless your heart, you CAN sell of gunbroker or auctionarms. But when it is purchased, the buyer needs to send you the name, address, and license number of HIS FFL he wants you to ship the gun to.
Now, it is not required that you ship a gun FROM a FFL (except pistols going into NY State must come from a FFL to a FFL) HOWEVER- the cost of shipping a modern handgun will make you weep. You may want to find a dealer that you can pay to ship for you- THEY can use US Mail- you cannot. If you ship yourself, must be UPS or FedEx Next day Air- and will cost you about $75.
You can also check and see if there is a local dealer that will sell your gun on consignment for you.
What we have here is... failure- to communicate.