different strokes for different folks
I hold a 03 FFL, which is Curios & Relics so I can sell to out-of State buyers like everyone else, but I can only SHIP to full 01 FFL's or other holders of valid 03 FFL's.
OK...that's the way it is...the trouble arises when I actually go to Ship the firearm. Local Fed-Ex WILL TAKE IT as long as the wrapper is plain with no logos, or id of what's inside. However...Fed-EX is by far the most expensive, especially adding full insurance, and next day air...which is the only thing local Fed-Ex will do for me.
UPS is no good for me (and I have tried several UPS stations, not franchise kiosks either). I have to declare what's being shipped, the "ship to" is the buyers 01 FFL, and invariably, the buyers FFL is an address that starts with Joe Schmo Guns", Jack's Sporting Goods" or some other semi identifier that says "gun inside" so they reject me.
The LGS and other full 01 FFL's right around here have daily or weekly UPS route pickups so there is no question, the driver knows the firm and knows everything is packaged and off it goes.
Another problem like posted above is that even with my 03 C & R, the Buyers FFL sometimes (most of the time) won't accept inbound from anyone other than another full 01 FFL
We have only 1 local LGS that does outbound transfers and they are $75.00 before shipping costs and insurance so quite steep vs the $25 of days gone by when there were 4 competing LGS, but it is the only game in town, and still the safest, fully legal way with peace of mind for all parties involved.
I've sold and shipped rifles, shotguns, and handguns, but I like to take pride in shipping exactly what condition I would expect to receive if I were buying. I liked it when I could wipe down, package with proper bracing, protection and wrapping, stiff, new cardboard shipping boxes. Cost me very little, yet the firearm didn't arrive with fingerprints all over the bluing, rust from some LGS employee checking serial number with greasy pizza hands, etc.
Unfortunately, once you sign it over to the FFL for shipping it is now on his books, off of yours, and how and what materials he uses to ship, or care (or lack thereof) that his employees give it is out of your control, but it is still the only way for me anyway.
USPS? Forget it! Even the local postmaster won't take firearms no matter what, even if I try to point out written materials from USPS, and have the proper form filled out....they just say no.
Face-to-face where legal remains the best way in my opinion, but the OP just wants to sell and ship to wherever the buyer is so I'm saying 01 FFL to 01 FFL is probably the best bet.