You are from Virginia going to Pennsylvania -- I should point out you are going THROUGH the State of Maryland -- you should talk to Dreamer more about this, but for the love of all things good and holy -- BE CAREFUL IN MARYLAND.
OR you should NOT talk to Dreamer if you don't want to be made completely paranoid of and disdainful for MD...
The MD AG has stated officially and FOR THE RECORD that MD does not recognize a RKBA. That alone should be "nuff sed" for anyone thinking about transporting firearms through the PRM...
But if you MUST drive through MD with a firearm, here is the deal...
Unloaded, locked up and inaccessible by ANYONE in the vehicle is the only legal way to do it. The ammo should be stored in a separate container, but it doesn't have to be locked. Also, magazines or speed-loaders CAN be loaded, but NOT stored in the same container as the firearm.
If you DO get pulled over for some traffic infraction (real or imaginary) and you are in one of the "4 Urban Counties", you will almost ALWAYS be asked if you have any firearms in the vehicle--especially if you have VA, WV, PA or NC plates. You have TWO choices here:
1) simply don't answer. You can NEVER say anything that will help you with a cop in MD--even if it is the truth. Don't lie--that is BAD. But not answering such a question is not illegal and does not constitute any offense, and is in fact protected under the 4th and 5th Amendments. However, be aware that ignoring such a question and not answering MAY be interpreted as "contempt of cop" and could very well get you detained, arrested, beaten and charged with any number of ridiculously fabricated violations, or
2) tell him the truth, and be prepared to be sitting there on the side of the road for at least an hour, while they search your vehicle, and maybe even bring in a K-9 unit. This will probably result in your paint job and interior being damaged, and perhaps even the confiscation of your firearm. If you can afford that sort of abuse, theft and vandalism, (and find it preferable to the sort of "street justice" that MD LEOs routinely hand out for "contempt of cop") then just tell them "yeah, I've got firearms".
I have been pulled over once while living here. I had a "Guns Save Lives" sticker and a VCDL sticker on my vehicle. It was a MoCo officer that pulled me over (expired NC tags) and he did NOT ask me if I had firearms. I think he was so excited about writing a $70 ticket for the tags that he didn't even see my stickers, because the MD AG and MSP have issued official policies in the last year that the presence of ANY pro-2A stickers on a vehicle constitute "elevated threat levels" and are grounds for "exercising extreme caution for officer safety", especially if they are on a vehicle with out-of-state tags.
I was fully expecting to get the "full monty" because of my stickers, but for some reason, I didn't. Perhaps it was because of my iPhone sitting on the dashboard, with an audio-recording app clearly running on the screen--I don't know. Heck, for all I know, my name comes up n the MD database as being some sort of "well-versed 1A/2A Activist" an there is a "do not provoke" tag on me.
Anyway, the bottom line is if you can avoid MD, DO IT. If you can't avoid, then gas up and eat before you "cross the moat" out of VA. There are plenty of places to eat and get gas in VA on the MD border. Stopping presents the risk of being spotted and harassed by LE.
AND if you engage in commerce in MD you are giving tax money to the MD State Treasury, which goes to further their restrictive regime here "inside the moat". Every penny spent in MD goes toward further 1A, 2A, 4A and 5A restrictions of MD citizens and any wayward travelers who may have the misfortune to cross the border into this god-forsaken serfdom.
One more thing--
if you travel through MD with firearms, the BEST thing to remember is to simply NOT give any LEO the excuse to pull you over in the first place. Have your tags up to date. Make sure your lights are all working properly. Drive safely and follow the speed limits and obey traffic laws. And don't stop unless you ABSOLUTELY have to.
Good luck with your trip....