Thoughts on Microstamping

For many people ((Usually non-shooters.)), the idea of microstamping makes sense, at least at first: spent casings would be marked with some unique markings that would correspond to the precisely gun that fired the round, thus allowing the police to more effectively investigate crime.
Of course, such a plan as several flaws:

1. There are lots of non-microstamped guns out there. It’s likely that criminals would be able to avoid acquiring such guns.
2. There are plenty of guns being made in the world that would not bother microstamping. If a black market arises for non-stamped guns, I’m sure that someone will supply the market — they already smuggle illegal drugs and other contraband.
3. Criminals are not going to purchase their firearms through legal channels, and thus associate the stamped serial number with themselves. They’re probably going to just steal the guns, much as they do already.
4. Thoughtful criminals could acquire range brass and sprinkle it around a crime scene, thus confusing investigators. It would also open up some identity theft concerns for law-abiding shooters who don’t police all their own brass.
5. Revolvers do not eject spent brass when fired, and so it would be simple for a criminal to use a revolver in the commission of their crime.
6. Firearm microstamping equipment is currently produced by only a single company, is not inexpensive, would increase the workload for firearm manufacturers, and would add to the cost of new firearms.
7. Investigators would only be able to trace the gun to its first lawful owner; if the gun was subsequently lost, stolen, or otherwise not in the possession of the original owner, it is unlikely that identifying the first owner would be of any use. (Indeed, if the gun was stolen, the lawful owner is likely to have reported that information to the police, and thus the gun would be listed in the NCIC stolen gun database — this is accessible by any police department in the country.)
8. Parts wear out normally from ordinary use. Tiny markings are almost certainly prone to wearing out sooner.
9. It is trivially easy to defeat firing pin microstamping: firing pins are replaceable, and thus can be removed from the gun. A few passes with an inexpensive diamond file can remove markings from even the hardest steel. One could also buy a replacement firing pin (such as this one for my Glock 19), or even make one’s own pin with only basic machine tools.

Many guns don’t require any sort of tools to disassemble, and it’s rare to require anything more than the most basic hand tools to replace the firing pin. For example, I was able to get the firing pin out of my Glock 19 using only a Bic pen in about 14 seconds:

Taking the spring cups and spacer sleeve off the firing pin takes about 5 seconds, and putting them back on takes maybe 20 seconds (stupid spring cups are tiny). Reassembly takes about as long as disassembly, but requires the blunt end of the pen in addition to the pointy end.
It should be obvious to a reasonable person that, when confronted with reality, microstamping is a non-starter. Of course, that didn’t stop California from passing a microstamping law into effect.
Additionally, California’s microstamping law specifically exempts the police, the one group for whom microstamping would be useful — microstamping departmental guns would be useful in situations where the police shoot at someone. Having police duty weapons leave unique markings on brass would probably help investigators piece together crime scenes better. Due to the small number of weapons involved in a shooting incident, it should be rather easy to figure out which brass corresponds to which gun, even if the stamp is a bit worn or certain characters are unreadable. Departmental armorers could regularly inspect and replace stamping firing pins as needed — something that would be impossible to enforce for the general public.