Microstamping Bullets
The idea is that every bullet, case, and box of ammo has a unique serial number that is tracked in some kind of database.

1. There are millions (if not billions) of rounds out there already, without any serial numbers.

2. This is a non-trivial database task. A 32 bit hash can only store 4.3 billion numbers. Every manufacturer would have to be assigned a block of serial numbers to prevent duplicates. These numbers would have to fed into a central database at the point of sale.

3. This scheme is defeated by stealing ammunition.

Microstamping Firearms
This idea is that each firearm stamps any cases fired with a unique serial number. This has all of the same problems as the stamping of bullets only on a smaller scale.

1. There are millions of firearms already in private hands without this technology.

2. Modification of the firearms could distort or remove the stamping.

3. This scheme is defeated by stealing firearms.

4. This scheme is defeated by modifying the parts that stamp the cases.

5. Currently the projected cost of adding microstamping technology to a firing pin is about $250 per unit.

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