And make sure you don't have any bullets or even empty cartridges in the car. If for some freak reason they search your car and find anything.....ANYTHING gun related your goose is cooked. Play it safe and just don't take it and clean out the car.
I have a friend that took a gun into DC once. He left it in the car, in the hotel basement parking garage. And that's where it stayed for the duration of his trip until the day they left and continued on with his journey. Fortunately there were no traffic violations etc. so he wasn't stopped and checked over. It's Russian roulette.