[nonDosearrany]

DanS -- the wiki page for firearm microstamping discusses the technology pretty extensively. Sounds like it is (arguably) pretty effective and relatively cheap

But here's something I hadn't thought of...

It would also be possible for someone planning a criminal act to obtain fired casings with markings from a shooting range, for planting at the scene of a planned crime, erroneously linking unrelated gun owners to the crime scene to introduce doubt in any subsequent jury trial. Likewise, range brass, acquired at a range and reloaded, would still be marked with confusing markings on the head of the cartridge case, even after reloading. As not all bullets recovered from crime scenes are intact, which can prevent matching striations, these twists would introduce considerable confusion in processing and prosecuting criminal edit: xpost