The micro stamp idea is about as impractical as gun bracelets that are supposed to ensure that only authorized owners of the weapons can fire it.
1. Gun manufacturers won't do it as customers could not afford it, and they certainly won't do it just for the CA market;
2. If it ever became law, the millions of existing guns in the state or nation as a whole would just become more valuable;
3. if the government outlawed those older guns, it still won't take them out of the hands of criminals, who don't mind breaking the law already; and
4. if by some means the government successfully confiscated the millions of guns already in CA or the US as a whole, it would just create an incredibly lucrative market for smuggling in illegal arms for criminals (remember how well prohibition worked). Given that we can't even keep illegals, out, we certainly can't keep guns from crossing our borders.
Any way you slice it, no matter how good these ideas sound to the non thinking, non gun public, criminals maintain access to firearms and honest laws biding citizens lose access to them.
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I've considered starting a rumor about a proposed bill in CA where they require a miniature digital camera in the base of each bullet aimed backwards so that it then takes a picture of the shooter so that police can recover the image file with the bullet. It could probably be done for maybe $200 per round, or just $1,600 for a fully loaded low capacity 7+1 self defense pistol.
Of course...I've never followed through with this as the PRK politicians might think it's a good idea.