Re: Question on selling long gun.
unless you are in the business of selling, there should be no problem. However, if investigated, a BATF agent would make lots of mileage on why buy a gun if you already have one, UNLESS you intended to peddle it off or it was a straw purchase. Even though there is no requirement to go through a dealer, you may want to consider that. Solves the straw purchase potential and keeps you out of trouble if the buyer turns out to have a problem having a gun. Just talked with a guy this week who pled guilty to stalking and of course he says his lawyer never told him that such a conviction would prevent him from possessing firearms.
Don't know how well you know the buyer. Could he have been committed without your knowledge? Might he have a domestic assault conviction lurking in his past? You could be drawn in if you do not at least run a check on him yourself.