Um, last I saw, possession of a stolen firearm was juast as bad as claiming ownership. If you are caught with it, you are caught with it. If the cops go to your uncle and ask where the firearm is and he says you have it (not that he is ratting you out, but because they really are going to insist he tell them what happened to it), then you are implicated, and the chain of custody ends with you. I would, in that case, expect to be charged with receiving a stolen firearm, or worse.