-Microstamping does not work if shell casings aren’t automatically ejected from the crime gun. Revolvers, derringers, double-barrel shotguns, pump shotguns and rifles, and semi-automatic firearms that can be equipped with inexpensive brass catchers (common among some shooters) would leave no cartridges at the scene of a shooting.
-Microstamping does not work because firing pins are inexpensive and easy to replace. The firing pin for most weapons are easily replaced by someone with a minimum of ability to read and follow the basic cleaning directions for his firearm. The expense of millions of dollars in retooling is thwarted by the purchase of a $12 part.
-Microstamping does not work because the stamping is easily defaced. It would take a matter of a half-dozen passes of a standard diamond file, and less than a minute, to eradicate the microstamping.
-Microstamping is incredibly fragile. The stamping would wear out over time through simple use of the firearm, or be thwarted by the normal powder residue that builds up on small parts.
-Microstamping could easily be spoofed and waste police time — or worse, send the wrong people to jail. Most shooters do not reload their own ammunition, and leave their shell casings at the range. All it would take to turn microstamping to a criminal’s advantage would be for a criminal or one of his associates to pick up brass from a firing range in the same caliber as the weapon he carries. After he uses a microstamping-free weapon in a crime, he would merely drop the brass he recovered from Joe Citizen at the range at the crime scene. Joe will wake up with a SWAT team crashing through his door at 5:00 a.m., and if he’s lucky, innocent Joe won’t be gunned down along with his family pets.