[LoneRangerMassachusetts]

The firing pin that stamps the cartridge will either have to be so soft that it could be easily erased, or so brittle that it could break, he said.

Explain this please.

[amchugh]

Brass is hard, to stamp an imprint into brass would in theory require a very hard metal or alloy, which is typically more brittle. If the alloy or metal which stamps the brass is made softer, it will leave a poor impression, and with repeated firing will wear away until it leaves no impression at all.

Anyway, this sounds pretty stupid to me, if your objective is to "fingerprint" ammunition wouldn't you want to stamp the bullet instead of the casing, or just require the manufacturer to test fire one round and send it to the CA authorities to have the rifling pattern logged into a database.