YouTube user "Xtamared" built a partly 3D-printed railgun that can fire aluminum or graphite projectiles at over 250 meters per second (560 mph). No, this isn't Quake, and it's no janky, all-plastic weapon, either. The "handheld" weapon houses six capacitors that weigh 20 pounds and deliver over 3,000 kilojoules of energy per shot. And it indeed works just like a full-sized railgun, using parallel electrodes to fire an "armature" bullet. The creator used an Arduino Uno R3 to monitor charging levels, temperature and other factors, and had to modify the rails after he noticed "plasma damage."
Source: Xtamared (Imgur)