And just for good measure, from the office of the California Attorney General:
Nonconcealable firearms (rifles and shotguns) are not generally covered within the provisions of California Penal Code section 12025 and therefore are not required to be transported in a locked container. However, as with any firearm, nonconcealable firearms must be unloaded while they are being transported. A rifle or shotgun that is defined as an assault weapon pursuant to Penal Code 12276 or 12276.1 must be transported in accordance with Penal Code section 12026.1.
http://www.ag.ca.gov/firearms/travel.php