Note: I am a biologist by training. But I know this last sentence is ridiculous: 塑胶 can not be a projectile of a railgun. See railgun
("The railgun uses a pair of parallel conductors, or rails, along which a sliding armature is accelerated by the electromagnetic effects of a current")
Click "armature" and one will learn, "The armature must carry current, so it is always a conductor."