If it passes both houses and Jerry Brown signs it, it will be challenged in court and an injunction against it will be put in place immediately.
Another ammo law was overturned as unconstitutional a few years ago, thanks to CalGuns Foundation and SAF.
I no longer have any faith in the Supreme Court. Since we can now be taxed by our masters for not buying a product, I see no hope that they would overturn this kind of law. California isn’t saying a resident can’t buy ammunition, they just want you to pay for the privilege.