Nuclear-Tipped Ion Cannons?

I know a little bit about rail guns and ion cannons, but there is something i have recently thought of.

would it be possible to have ion cannons that fire nuclear tipped rounds? i ask this because the material used (uranium, plutonium, whatever) may be too heavy. also the stress of travelling at velocities approaching the speed of light may cause a reaction from the material used

any ideas?

The rounds fired from railguns do not hold their shape. They start to melt. There could not be any explosives. The rail gun would perform like the DU rounds in the tank.

"Ion cannons" do not fire solid projectiles per se.

Ion Cannons refer to a charged particle weapon of some kind. This is where a stream of high energy charged particles are fired at very high velocity by a magnetic field of the opposite polarity. The relativisitc velocity of impact along with the often very high energy charge load is what does the damage from these weapons.

Charged particle weapons would have very limited use on the ground as they would dissipate thier charge as they are fired through the air, and would basically use up the energy load ionizing the surrounding air rather than on the target.

Rail Guns refer to an electromagnetic cannon, firing a solid projectile using electromagnetic propulsion. In this case, the cannon "barrel" is often 2 conductors charged to very high voltage, and the projectile acts to complete the circuit. When the circuit completes, it forms a very high electromagnetic field which fires the projectile at velocities approaching relativisitic (low end) velocities.

To date, there have been no attempts to use conventional high explosive warheads in rail guns because A, all such rail guns have been of such small diameter as to preclude the use of any useful amount of chemical explosive, and B, because the kinetic energy developed at the ultra high velocities is in excess of what can be delivered by a chemical explosive.

To my knowledge, the "melting" of the projectile in railguns is a function of the high voltage arc across the projectile, and not due to the high velocity. I would believe that a properly constructed projectile, with sufficient insulation between the conductor and the main projectile body, would allow the projectile to remain intact for the entire trip. In this case, assuming a projectile large enough to house the warhead, it would be feasible to fire a small tactical sized nuclear warhead.