No doubt such transactions occur every day, but that doesn't make them legal in the eyes of the ATF. Unless both parties are residents of the same state, the transaction must go through an FFL in order to conform to the requirements of the law. Here is an excerpt from the ATF faq section:
"(B1) To whom may an unlicensed person transfer firearms under the GCA?
A person may sell a firearm to an unlicensed resident of his or her state, if the buyer is not prohibited by law from receiving or possessing a firearm, or to a licensee in any state.
(B2) From whom may an unlicensed person acquire a firearm under the GCA?
A person may only buy a firearm within the person's own state, except that he or she may buy a rifle or shotgun, in person, at a licensee's premises in any state, provided the sale complies with state laws applicable in the state of sale and the state where the purchaser resides."
I'm not saying I like it or agree with it, and I'm sure it is routinely ignored, just like the speed limit. And I have no idea what additional requirements NJ or MD may impose, if any. But you should know what's legally required and consider the consequences before you decide how you want to proceed. James Fawcett