I can't speak to MD or VA law, but under federal law it may be ok. FWIW, I don't think either MD or VA have any state law prohibitions that would prohibit such a sale, but I'm not 100% sure.
Under federal law, however, it would be permissible to buy the lower in VA if (and only if) at the time of sale it was logged out as a rifle and you didn't assemble it as a pistol. Under federal law an FFL in one state can sell long guns directly to the resident of another state if there are no state law prohibitions to the contrary and the sale complies with the law of both states. Neither an FFL nor a private individual in one state may sell a handgun directly to an individual in another. Thus, if you intend to assemble it as a pistol, have the seller send it to an FFL in your state to transfer it to you. If you only intend it to be used as a rifle, then you can probably buy it directly from the FFL in VA.
