Maryland does not recognize any other state handgun carry permit.
There are restrictions on sale and import of "assault rifles" and a ban on "assault pistols" (like the TEC-9) but there will be no problem with an ordinary shotgun or sporting rifle, even a semi-auto (e.g., Remington 7400).
You can bring a handgun into MD under FOPA and keep it in your residence with no permit or registration required, but transporting or carrying it in the state without a permit is restricted - to/from a range or informal shoot, to/from a place of sale/repair, etc.
MD has no "castle doctrine" or "stand your ground" laws as such, but there is a widely accepted body of law which is basically common law. You can defend yourself in your home against a threat of death or GBH; any illegal intruder can be assumed to be a threat because he is in your house. (As always, anywhere, make sure the "intruder" is not your girlfriend or the meter reader.) Outside the home is problematical, since a handgun carry permit is almost impossible to obtain.
Jim