I've never had a problem selling a gun for the price I want, using forums like this or word of mouth, and armslist, all face to face sales. I wouldn't pay gunbroker, unless maybe the shotgun is really expensive and you want a larger bidding audience.

Excluding pistols, the US postal service will ship from you to someone directly in the same state, or to an FFL if crossing state lines.

If you wanted to ship a pistol, in state or out, I think you will end up shipping from an FFL to an FFL, as I don't think a carrier will take a pistol from a private person.

I could be wrong.

What ya selling?