Good one, amigo. Keep thinking good thoughts.
The purchase by gift card proves the receiver of the gift card was not in profit-making mode (hence no fed or state income taxation); and the giver of the gift card (and new possesser of the gun) is not subject to sales tax. IIRC
Remember, we're now talking of maybe a few hundred dollars of value -- and if no exchange, the gift cards can still be used to buy something else.