I remember reading about this type of artillery round while in the Army. A depleted uranium 'slug' was buried inside an artillery round, and at some point in its trajectory a secondary round would fire, providing additive velocity to the 'slug', whose energy increased by final-velocity squared... delivering a powerful punch. When it hit the side of a tank, there was only a small puncture wound outside, but it broke off a huge chunk of metal inside, which then became a shrapnel factory. Nasty stuff.