California law specified that the gun must be unloaded and in a locked container. I'm not sure the law explicitly speaks to ammunition or loaded magazines but it is my recollection that case law holds that ammunition is allowed in the same container, but loaded magazines are not. My recollection is also that it is ok to have loaded magazines elsewhere in the vehicle, just not in the same locked container that contains the firearm. Disclaimer, I'm not a lawyer, I just live in California. When I transport handguns to the range they are in a locked metal box that contains no ammunition and I don't carry loaded magazines in the vehicle.
Here is some light reading for your consideration.
from
http://ag.ca.gov/firearms/travel.php
HANDGUNS
California Penal Code section 12025 does not prevent a citizen of the United States over 18 years of age who is not lawfully prohibited from firearm possession, and who resides or is temporarily in California, from transporting by motor vehicle any pistol, revolver, or other firearm capable of being concealed upon the person provided the firearm is unloaded and stored in a locked container.
The term "locked container" means a secure container which is fully enclosed and locked by a padlock, key lock, combination lock, or similar locking device. This includes the trunk of a motor vehicle, but does not include the utility or glove compartment. For more information, refer to California Penal Code Section 12026.1.
And here you can find the section 12026.1
http://caselaw.lp.findlaw.com/cacodes/p ... 12040.html
12026.1. (a) Section 12025 shall not be construed to prohibit any
citizen of the United States over the age of 18 years who resides or
is temporarily within this state, and who is not within the excepted
classes prescribed by Section 12021 or 12021.1 of this code or
Section 8100 or 8103 of the Welfare and Institutions Code, from
transporting or carrying any pistol, revolver, or other firearm
capable of being concealed upon the person, provided that the
following applies to the firearm:
(1) The firearm is within a motor vehicle and it is locked in the
vehicle's trunk or in a locked container in the vehicle other than
the utility or glove compartment.
(2) The firearm is carried by the person directly to or from any
motor vehicle for any lawful purpose and, while carrying the firearm,
the firearm is contained within a locked container.
(b) The provisions of this section do not prohibit or limit the
otherwise lawful carrying or transportation of any pistol, revolver,
or other firearm capable of being concealed upon the person in
accordance with this chapter.
(c) As used in this section, "locked container" means a secure
container which is fully enclosed and locked by a padlock, key lock,
combination lock, or similar locking device.