On microstamping gun cartridges

Apparently, many chiefs of police are eager to require new firearms to have a firing pin which will "micro-stamp" a unique ID onto spent cartridges, and cannot figure out why anyone would object.  Well, let's look at the evidence.

For starters, the method is useless if the crime gun is a revolver (a large portion of crime guns, #1 and #6 on the FBI list), where the cartridges stay in the firearm until removed by the owner.  Going further, as the article admits, the serial number is only visible half the time, and the best identification studied is "most of the time"--and that with new firing pins, not worn tool steel.  It's worth noting here that identifying a gun by the marks the firing chamber leaves on the outside of the cartridge tends to be just as effective.

It's also worth noting that firearms, unless heavily used, last a long time, so requiring new firearms to have this feature doesn't make a big difference quickly. I personally own a .22 rifle that is over 100 years old and still works wonderfully. 

Finally, tracking firearms by serial number only works if the firearm is traceable--and in a world where most criminals get their gun via theft or a private sale, one simply cannot do this.  So what we would have would be a very expensive way of tracking very few criminals--but a very inexpensive way of infringing on the rights of the law-abiding gun owner.