Just got an email from a friend that spent a day shooting with me and was covered with powder residue: So, with regard to the response of an airport hand swipe sniffer thing to having spent a couple of hours firing hand guns, the answer is: it did not register. I warned the two security people that I had been at a gun range and asked if it would matter, and they actually didn't know the answer and were as curious as I was at what would happen. I don't know if they were as surprised as I was at the result, but the machine didn't care. I don't know what that means, but it's curious. I wonder if it's just an empty plastic box with lights and buttons that doesn't actually do anything, and is just there to scare/re-assure people.