In Florida, a firearm can be carried in a vehicle in any compartment or container that requires a lid or cover be opened or removed to gain access. The law also itemizes a snapped holster as meeting the requirement. A closed pizza box on an unoccupied passenger seat would even meet the standard.
However, the container holding the firearm can not be on one's person without a valid carry license or permit honored by the State.
A long gun may be stored and transported in any location, visible or otherwise, in a vehicle, provided it is not carried on one's person, or so close to one's person as to be as readily-available as if it were on the person; this would violate the State's ban on open-carry (or concealed carry if the firearm is not visible to the ordinary sight of another person.)
Unlicensed carry of a firearm (openly or concealed) is permitted in the following circumstances:
While engaged in, or traveling directly to or from, a lawful hunting, fishing, camping, or shooting activity.
While at one's home or place of business.
Florida does not differentiate between "loaded" or "unloaded" firearms in these sections of the statutes. Any firearm in the contexts of this post may be loaded or unloaded.
Keep in mind that Federal law still prohibits driving through a school zone with a firearm, or otherwise being in a school zone with a firearm, without a carry license or permit issued by the state in which the school zone is located. This is a law that is practically impossible to follow while traveling with a firearm, but I know of no prosecutions of violators who did not otherwise break other laws that drew attention to themselves.
