I'm in Northern Virginia and often cross into Maryland, and seldom into D.C.
I have had my CCW in Virginia since they were first issued in 1997.
I never have a weapon when I cross into either locale. It is illegal to do so. Forget D.C. under any situation; and keep in mind, in D.C. ammo is considered a weapon! I usually have a couple of 20-round boxes of ammo in my console.
Once I forgot to remove them, and went to an event at the Verizon Center. The valet guys could have been nosey and discovered them.
I'd be in big trouble.
This is the most idiotic set of laws I know of, but it is what we deal with living next to to non-free states.
It sucks, but unless you want to risk losing your weapons, maybe even your job, if they want to make an example of you and search your home as well.