I saw this today on Wikipedia:
The United States military is funding railgun experiments. At the University of Texas’ Center for Electromechanics, military railguns capable of delivering tungsten armor piercing bullets with kinetic energies of nine million joules have been developed (http://www.iat.utexas.edu/electrodyn.html). Nine million joules is enough energy to deliver 1 kg of projectile at 3 km/s – which will tear a tank to pieces in a single shot.
Railgun – Wikipedia, the free encyclopedia