Face-to-face firearms transfers in Florida are legal when both parties are Florida residents. A Florida resident can sell a handgun to a resident of another state, but the handgun must be transferred through FFL locations, sent from one to another in the recipient's home state.
Federal law does not prohibit the transfer of an antique firearm across state lines. For the purposes of the law, an "antique firearm" is a firearm manufactured before 1899, or one manufactured after 1899, but replicates in appearance, operation, and ammunition, one manufactured before 1899, and uses only "rimfire or conventional centerfire fixed ammunition which is no longer manufactured in the United States and which is not readily available in the ordinary channels of commercial trade", (or uses a loose-powder loading system, such as a "blackpowder" gun.)