Checking reciprocity for your carry permit is one thing, but often states will have a traveler's exception for carry inside a vehicle. It usually applies only if you are a specified distance from home. Once again, you have to check state by state. Also some states, like Louisiana, allow anyone who can legally possess a handgun to carry it loaded in the glove compartment of the car as it is considered an extension of the home (never really understood the rationale, but it is good for CCW'ers.)