Comment by chipsa

The armor and projectile are solid the entire time. It’s just the pressures involved are enough to make the material flow despite that. Actual experiment: cut the rod into quarters long ways, glue it back together, then shoot it. Out the other end of the armor, the rod is in quarters still. Or at least, what’s left.

Also, most materials will burn at a high enough temperature. DU dust is pyrophoric: it will spontaneously catch on fire at room temperature.