The Brady Bunch has a link to this video about "microstamping" on their website. They ignore obvious and important points of their critics such as:

• Shell casings found at a gun range can be deliberately scattered at a crime scene
• Revolvers don't leave shell casings at the crime scene unless the shooter reloads
• Replacement firing pins and breech faces would have to be registered and tracked as well as the firearm itself
• Gun parts are easily modified or manufactured
  • Firing pins can be manufactured from scrap metal with simple hand tools--they may not last more than a few dozen shots but they should be more than adequate for most crimes
  • Breech faces markings can be ground off and/or filled in with metal filled epoxy
• There are many millions of guns already in circulation
• Stolen guns aren't going to be associated/registered with the criminal who used it in a crime
• A black market will likely develop in unmarked gun components or components that have phony numbers (such as fake SSN cards that have valid numbers but belong to someone else)

One must assume they believe in some sort of supernatural capabilities for this technology that defies the laws of physics and human nature as we know it. But regardless of all the reasons why this scheme could never work the big thing that I noticed while watching this video was the background music--the theme from The X-Files.