thats not a rail gun though its a stun gun, a rail gun uses electric pulse to move a metal bar through a barrel, so far none have been made that are practical. But those stun guns are fun, you can also make one out of a battery powered bug zapper, these done actualy stun but hurt like hell.
Both are rail guns. One is a very accurate firearm w/o a stock and one is an electric pulse gun with EXTREMELY high velocity (11,000 fps or so). The UT research center (now called the J.J. Pickle Research Center, crooked former US congressman from Austin) is here in Austin. They have been at the forefront of the electric rail gun technology race. I know some guys that work there and the velocities they get are incredible. A piece of plastic weighing about a half pound going over 10K fps has incredible kinetic energy. The shortcoming is and will be the amount of power needed to drive it that fast. They have a nuclear reactor there so I guess power is not a big issue.