What's the CA definition of an "assault" weapon?
Any semiautomatic rifle or carbine with a removable magazine.
It took at least three different laws before the anti-gunners here in Kalifornia were able to satisfy their need to outlaw constitutionally-protected behavior.
The first outlawed a whole list of scary, militaristic guns by make and manufacturer. When it became obvious that this was not sufficient, they added a law which permitted the Kalifornia Attorney General to add weapons to the list as he saw fit.
When it was realized that new manufacturers could create new models faster than they could be listed, Kalifornia passed a law outlawing center-fire, magazine-fed, semi-automatic rifles with any ONE of various features, including pistol grips, collapsible stocks, forward pistol grips, or those really scary flash suppressors.
When it was realized that gun-owners could buy unlisted receivers HOPING that Kalifornia would add them to the list, permitting them to own an "assault weapon" after the grandfathered cut-off date, Kalifornia removed the Attorney General's authority to add rifles to the list.
When Kalifornia realized that .50 BMG rifles are powerful and scary-looking, they too were added to the list. This despite their never having been used in a crime.
When the law first appeared, I sensed trouble ahead and arranged to store five of my rifles out-of-state. One of these was a $2000 target rifle.