Another thing to consider is that if you decide to declare yourself a resident of PA (as in, PA driver's license, paying PA income taxes, etc.), you will have an easier time purchasing firearms than as a resident of NJ. When you are done with school, you can always move back to NJ (though I don't know why you'd want to), and, as long as the firearms are legal to possess in NJ (as I mentioned above with NJ's assault weapons ban), you may legally bring them into NJ, and you do not need to register them or anything.