From what I understand (and I admit, I'm not an expert), MD has NO reciprocity with ANY states. MD is very gun un-friendly.
I live in VA and I can open carry (without a permit) or concealed carry (with a permit - "shall issue"). But, 10 miles up the road, across the border into MD, there's no permit I can get that will allow me to legally carry in that state.
When I bring guns into MD, they're always cased, locked, ammo separate, and don't stop for gas/food/whizzing on your way out of the state.
Just to give you an idea of how bad MD gun laws are, The Maryland State Police maintain a registry of "regulated firearms" that are allowed to be sold within the state. So, just because Glock comes out with a new handgun model...doesn't mean you can BUY one. No, you have to wait until the state police get around to deciding whether you can, or cannot, legally purchase one.