https://oag.ca.gov/system/files/attachments/press-docs/consu...
when should you be required to serialize it?
if you serialize after it is worked to the point of being a firearm, then there is a period in time, however short, when the firearm is unserialized, thus illegal, thus serializing after creation could be obscuring a crime.
vs serializing before firearmhood, and you are now requireing a "hunk of metal" to be serialized because of what it MAY become in the future.
and just when does a hunk of metal start becoming a firearm, the so called 80% threshold
The rest of the stuff? You can buy and overnight ship it to yourself legally with almost no regulation (as of 2026 CA requires more gun-like treatment for those parts).