I bet its someone from the military selling those. Risky business. Or they could have bought them in a DRMO lot.
When the AO's loaded up one of our helicopters with bullets they would tell the aircrew to dump whatever they did not use(in the ocean). That way the AO's would not have to inventory (count every sing bullet) anything when they returned. And also sometimes have to carry hundreds of pounds of bullets back down from the flight deck.