In a rather popular (probably because of the progressively hypnotic music) viral video, often just called 'the bullet video' we see debris of fragmentation bullets (starting at 1:00 minute) seeming (if you take an informal eyeball-integration of the collective velocities) to go much (much) faster than the incident projectile. [The early bullets are hard-jacketed, and those are not important.] What gives? I'm pretty sure most of the debris of some of those bullets is going much faster than the incoming slug itself. I would expect kinetic energy loss into deformation, noise, and heat would actually make the debris move rather much slower, even leisurely.