There are two kinds of legal issues with a "straw purchase."
1-- you lie on a federal tax document, the Form 4473. You said you were the gun's actual buyer when really you were just a bagman for the real behind-the-scenes purchaser who sent you on this mission to buy a gun for him.
2-- you helped a prohibited person obtain a firearm, and that's the reason the real behind-the-scenes buyer didn't buy it himself directly.
Issue #1 can't happen in a private party sale. It only comes up when buying from an FFL dealer.
Issue #2, however COULD come up in a private party sale, and it's actually a violation of the law for a felon or other prohibited person to sell a gun (even though it's equally illegal to keep it and NOT sell it!). So, don't be the selling agent for a prohibited person disposing of a gun, unless you get a court's order directing you to do so (which sometimes happens-- lawyers whose clients get convicted and become prohibited persons sometimes get tasked to sell the guy's guns for him (but not to buyers that he finds or sends to the lawyer).
1-- you lie on a federal tax document, the Form 4473. You said you were the gun's actual buyer when really you were just a bagman for the real behind-the-scenes purchaser who sent you on this mission to buy a gun for him.
2-- you helped a prohibited person obtain a firearm, and that's the reason the real behind-the-scenes buyer didn't buy it himself directly.
Issue #1 can't happen in a private party sale. It only comes up when buying from an FFL dealer.
Issue #2, however COULD come up in a private party sale, and it's actually a violation of the law for a felon or other prohibited person to sell a gun (even though it's equally illegal to keep it and NOT sell it!). So, don't be the selling agent for a prohibited person disposing of a gun, unless you get a court's order directing you to do so (which sometimes happens-- lawyers whose clients get convicted and become prohibited persons sometimes get tasked to sell the guy's guns for him (but not to buyers that he finds or sends to the lawyer).