Handgun, X-ray. Hand holding a Walther P99 semi- automatic pistol. The index finger is coiled round the trigger, ready to fire. The rest of the hand is holding the grip of the gun. The barrel is seen above the hand, and is where the bullet is fired out of the gun. This gun does not use a hammer to fire the bullet. Instead, the action is a recoil- operated dropping-barrel design. The body of the gun is made of a lightweight polymer. The firing pin has been removed from this gun, because it has been adapted to fire 6mm BB pellets. X-ray images are used by security teams to detect weapons like this being illegally smuggled into a secure area.