The key thing was that it could be built surreptitiously, making it so untraceable that it was the ultimate “ghost gun.” Many of its components are unregulated, unremarkable metal bits: springs, screws, nuts, washers. JStark1809 suggested places where they might be found, such as AliExpress, eBay or the hardware store McMaster-Carr. What couldn’t be bought could be printed—the grip, say, or the stock—or, like the barrel and bolt, could be machined at home out of purchased metal parts. The finished product looks, as one commentator described it, “like if a kid’s drawing of a pistol became a weapon.” It has a long stock and a short barrel, and it can be printed using any color of plastic filament; in Australia three years ago, police seized an FGC-9 with a bright blue barrel and an orange stock and trigger.