I have traveled to CA numerous times with non-CA compliant magazines.
UNLESS there is intent to leave, sell or trade them to someone in CA who is not in law enforcement, there is no law being broken.
Also having again taken long guns to CA that are not CA approved, f/hider, no bullet button, merely for my own shooting with friends, family other gun board members, there is no law being broken. I have done the same with guns going to NY.
If you have ANY QUESTIONS regarding what you can or cannot bring with you AND coming home with the same. Contact the CA DOJ.
OR go sign up, if not a member already on ARFCOM. Visit the CA hometown forum and ask them what you can or cannot bring with you.
THEY LIVE THERE and have a better understanding what is verbotten.
This is what i did after 2000 when driving to CA AND bring a few long guns with me.
This only applies to SEMI AUTO, LEVER BOLT OR SINGLE SHOT LONG GUNS & Shot guns.
NOT ANY NFA ITEMS Those, not even a blip on my radar to take them anywhere that NFA items are not permitted.