How traceable are bullets?

[inSight-NEO]

All of this talk about "traceable' bullets....First off, I can think of a handful of ways to defeat this (most are already known). Regardless, if I were to commit any type of gun-related crime, I would simply destroy the weapon and any ammo associated with it. Not to mention, I would opt for using a revolver (no ejected casings). Keep in mind, this would probably be a stolen weapon as well.

But, Im not a criminal... nor am I CSI. So, Im only throwing out hypotheticals here. Frankly, I have never given this sort of stuff much thought.