If you think the image above looks frightening, you’re right. The crazy contraption pictured in the image is the first portable railgun, a futuristic projectile launcher associated most commonly with the military or NASA. The man in the image above isn’t in the military, and he’s not a NASA engineer. Instead, he’s a civilian who used some engineering smarts, some widely available parts and a 3D printer to create a functioning weapon that can fire graphite, aluminum, tungsten and even plasma projectiles at speeds of more than 560 mph. And then there’s the best part: There are videos of this...