It depends, on others have said, on the state one is in.
In California, for example, despite having a concealed carry permit, all my firearms have to be unloaded, in a locked box, and locked in the trunk in order to be "legally transported."
That said, I can and do carry in Albuquerque and the rest of New Mexico. In Albuquerque, though, where car-jackings are pretty frequent, especially for pickup trucks, what I do is secure a holster to the hose clamp I've got wrapped around the steering column.
EDIT: It appears, though, that you're interested in stashing or
secreting firearms in a vehicle. If it has a trunk, a locked carrying case or box should be enough-Prius hatchback notwithstanding.
As it is, I don't see how I can install and conceal a secure safe that is large enough to hold a rifle in my Toyota Prius but I do know some places where I could possibly put in a hidden locked compartment that could hold handguns although it might have to be custom made.
.
Gotta be the funniest thing I've ever seen you post....:lfao:
Seriously, though-if you can lay down
a set of golf clubs back there, and you can, you can make a way to secure a rifle or shotgun.