Should be good to go then. A good friend of mine who is still stuck there has amassed quite a collection through the antique firearm exemption.
I knew I could find something more concrete than "Should be good to go" if I looked a little harder.
Check out this (older) link from calguns.net: http://www.calguns.net/calgunforum/archive/index.php/t-372142.html
The CA penal codes were renumbered about 5 years ago (allegedly without affecting the content) so the actual PC references in that link are out of date. I attempted to match it up with the current version but after a few minutes of this my head was about ready to explode.
I was able to find this to help make sense of the calguns reference:
https://www.atf.gov/firearms/firear...arms-ammunition-gun-control-act-definitions-0
In Title 18 US Code 921(a)(16), ATF says that an Antique Firearm is:
Any firearm (including any firearm with a matchlock, flintlock, percussion cap, or similar type of ignition system) manufactured in or before 1898
(plus some other stuff about modern reproductions which isn't relevant here)
So a breech-loading cartridge shotgun is covered, as long as it was made prior to 1899 and doesn't otherwise fall into the realm of the NFA (full auto, than 18" barrel on a shotgun, etc).
Also see http://www.calguns.net/calgunforum/showthread.php?t=1379130.
This very recent thread (9/17/2017) covers some of the same ground and includes (but doesn't expand upon) the new PC numbering scheme. It was originally about modern reproduction muzzle loaders, but they are considered antique firearms just like those manufactured prior to 1899.
So... an unloaded firearm that meets the federal definition of an antique firearm is not required to be transferred through an FFL.
Understand that I am absolutely positively NOT a lawyer. I simply pay attention to things like this because I have a lot of friends and family living there who seem to rely on me to interpret the lunacy that oozes out of their capitol.
I really appreciate the effort. 
