Unfortunately this is quite a derailment from a neat thread about a cool gun. Doubly unfortunately, yes, it certainly does sound like a violation of federal law. (Probably two -- counting the giver and receiver.) Unless your friend installed a gun safe at your house and locked his gun in it and took the keys with him, then possession (9/10s of the law as you stated) has indeed transferred from him to you. Since he's not a resident of your state, and you didn't (at least according to your description) do this transfer at a licensed dealer's shop on a 4473 form, that's not in accordance with the law. There is an exception for loans for sporting purposes, but those don't cover a "loan" that extends to the former possessor going back to his state and leaving the gun behind with the new possessor. Triply unfortunate, even removing this thread from public view wouldn't really make it undiscoverable. Please folks, try to understand the law (even though it's often complicated and non-intuitive) and be careful what you say online.