[SWAMPSNIPER]

The stamping is so fine that a piece of sandpaper placed on a fired case will obliterate it.

[FlyVet]

Yes, and what are they going to do, require periodical microstamping checks of all firearms? What's the penalty if your weapon doesn't microstamp properly?

If you lose a few pieces of brass, what are they worth on the black market? A criminal could deposit your brass at a crime scene, to throw off the scent.

None of that matters to a bunch of politicians, though. Not their problem.