The ONLY Maryland law pertaining to long guns transport is an obscure hunting statute that just says the long guns must be unloaded when in or on a vehicle.....that is all. Ammunition does not have to be seperate and long guns do not have to be locked, they just cannot be loaded.
There is serious doubt and question of if this statute applies to just when hunting or poaching though.
So for future reference, generally speaking you can transport your long guns in MD, under state law alone, to any location for any purpose in any condition just as long as they are unloaded when in or on a vehicle (boats are apparently not included in the definition of vehicles for that statute by the way). But if they are not in the open or are concealed and not cased and are immediately accessible (arms reach), it would be prudent to keep the ammunition seperate so an officer cannot claim it violates the concealed weapons statute. However, like I said, if it is in the open it is not concealed that law would not apply at all anyway.
You can avoid any possible police conflicts though by carrying the long gun in the trunk because in MD there is no legal requirement to have to tell the officer there is a firearm in the car and they cannot search your trunk without probable cause.
I am not a lawyer.