I wouldn't worry about it, it's not like ammo is registered to your name. Ask for cash payment and make use of common sense, if the person looks suspicious you can just refuse to sell, if it's someone you know personally I don't see any problem.
Remember this when you support the labeling and tracking of people and the complete digital takeover of commerce:
"It causes all, both small and great, both rich and poor, both free and slave, to be marked on the right hand of the forehead so that no one can buy or sell unless he has the mark, that is, the name of the beast or the number of its name" Revelations
"So you say your prayers and you thank the lord, for that peace maker in the dresser drawer"