South Carolina prohibits the possession, carrying or having readily accessible a loaded centerfire rifle, or shotgun loaded with a shot size “larger than number four” on a public road or railroad right-of-way if the person does not have permission to hunt the land immediately adjacent thereto.5 This prohibition does not apply, however, to a centerfire rifle or shotgun contained in a vehicle traveling on a public road, a closed compartment, or a closed vehicle trunk.6
And since I grew up there and continue to visit my parents there, I still see people on occasion, carrying rifles in racks behind the seat of their pickups.
If it were me I’d put the rifles where convenient and make sure it isn’t chambered.