MD Resident & Gun Owner
NEVER carry any guns in your car in MD. NEVER. NEVER. NEVER. NEVER. MD laws permit the carry of UNLOADED guns in the car but the guns & ammo MUST be separated physically. This means guns in the trunk, ammo in the glove box or console or in a bag on the seat or some other arrangement where the 2 can't be combined IN THE VEHICLE. Since I drive a regular cab pickup this presents major problems. There is no law I know of regarding magazines but you'll be arrested for having loaded magazines for sure. So DON'T have any. The law says unloaded handguns can be transpored in an automobile either in a closed container or a holster, but you'll be arrested for transporting an unloaded handgun in a holster for sure. If the long guns are visible you'll be arrested for them even if they are UNLOADED. The charges for any or all of the above are "possession of a deadly weapon on a public thoroughfare". You will also most likely be charged with possession of a concealed weapon (simply because it is in your car MD law claims it is concealed). MD law permits open carry of long guns in theory, but in practice you'll be arrested. Again "possession of a deadly weapon in public" will be the charge.
As to transporting guns to/from the range or sanctioned shooting event: DON'T. You will be arrested for it. As was noted MD laws REQUIRES you to travel DIRECTLY to/from your home to the range/etc without any stops. No gas, no phone calls, no groceries or bank/atm, no breakdowns, no accidents, no excuses. It is a ridiculous law, but that's what's enforced. If you go to the range you are better off to rent a gun than to transport your own. Trust me.
I'm not sure what the standards are for transporting weapons through/among the several states post-McDonald. The right to "keep arms" has not been clarified (yet?) so I wouldn't try it. I believe the Supreme Court ruled in McDonald that the RIGHT to keep & bear is a personal right enforceable against all states & their subdivisions. This means I can take my guns with me if I want. But this nonesense about any weapon in an automobile being "concealed" by royal decree means that there are more Supreme Court challenges before this issue gets resolved - if ever. Currently there is no Federal "Concealed Carry Permit" to apply for that allows citizens their 2nd Amendment RIGHT throughout the land, only Federal Law Enforcement and the US Military have this "permission". I don't think this will ever happen for the average citizen, at least not in my lifetime.