This is my ghost gun. To quote the rifleman's creed, there are many like it, but this one is mine. It’s called a 'ghost gun'—a term popularized by gun control advocates but increasingly adopted by gun lovers too—because it's an untraceable semiautomatic rifle with no serial number, existing beyond law enforcement's knowledge and control. And if I feel a strangely personal connection to this lethal, libertarian weapon, it's because I made it myself, in a back room of WIRED’s downtown San Francisco office on a cloudy afternoon. I did this mostly alone.