Federal law does not include 'antique firearms' as firearms for purposes of 18 USC 922.
California law is less forgiving; while transfer may be made without using an FFL, 'antique firearms' ARE firearms for purposes of transfer to and possession by felons, and for purposes of carry and possession by persons who are not disabled by law.
Generically a weapon made in or before 1898
CA Penal Code routinely defines Antique Firearm as those that are defined in USC 18, Sec 921(a)(16). In at least one place, CA Penal Code defines Antique Firearm as "made prior to January 1, 1899". In one area, dealing with "destructive devices", it defines it according to [Section 479.11 of Title 27 of the Code of Federal Regulations.] 
[USC 18, Sec. 921(a)(16)] reads:
The term "antique firearm" means -
(A) any firearm (including any firearm with a matchlock, flintlock, percussion cap, or similar type of ignition system) manufactured in or before 1898; or (B) any replica of any firearm described in subparagraph (A) if such replica - (i) is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition, or (ii) uses rimfire or conventional centerfire fixed ammunition which is no longer manufactured in the United States and which is not readily available in the ordinary channels of commercial trade; or (C) any muzzle loading rifle, muzzle loading shotgun, or muzzle loading pistol, which is designed to use black powder, or a black powder substitute, and which cannot use fixed ammunition. For purposes of this subparagraph, the term "antique firearm" shall not include any weapon which incorporates a firearm frame or receiver, any firearm which is converted into a muzzle loading weapon, or any muzzle loading weapon which can be readily converted to fire fixed ammunition by replacing the barrel, bolt, breechblock, or any combination thereof.
(a) As used in Sections 30515 and 30530, "antique firearm" means any firearm manufactured before January 1, 1899. (b) As used in Section 16520, Section 16650, subdivision (a) of Section 23630, paragraph (1) of subdivision (b) of Section 27505, and subdivision (a) of Section 31615, "antique firearm" has the same meaning as in Section 921(a)(16) of Title 18 of the United States Code. (c) As used in Section 17700, "antique firearm" means either of the following: (1) Any firearm not designed or redesigned for using rimfire or conventional center fire ignition with fixed ammunition and manufactured in or before 1898. This includes any matchlock, flintlock, percussion cap, or similar type of ignition system or replica thereof, whether actually manufactured before or after the year 1898. (2) Any firearm using fixed ammunition manufactured in or before 1898, for which ammunition is no longer manufactured in the United States and is not readily available in the ordinary channels of commercial trade.
Penal Code 16250 says
(a) As used in this part, "firearm" means any device, designed to be used as a weapon, from which is expelled through a barrel, a projectile by the force of any explosion or other form of combustion. (b) As used in the following provisions, "firearm" includes the frame or receiver of the weapon: ... (14) Sections 29800 to 29905, inclusive. ...
Penal Code 27500 is the prohibition on transfer to ineligibles:
(a) No person, corporation, or firm shall knowingly sell, supply, deliver, or give possession or control of a firearm to any person within any of the classes prohibited by Chapter 2 (commencing with Section 29800) or Chapter 3 (commencing with Section 29900) of Division 9.
Violation is punished according to Penal Code 27590
(b) If any of the following circumstances apply, a violation of this article is punishable by imprisonment in the state prison for two, three, or four years. (1) If the violation is of subdivision (a) of Section 27500.
Penal Code 29800 is the punishment for an ineligible in possession
(a) (1) Any person who has been convicted of a felony under the laws of the United States, the State of California, or any other state, government, or country, or of an offense enumerated in subdivision (a), (b), or (d) of Section 23515, or who is addicted to the use of any narcotic drug, and who owns, purchases, receives, or has in possession or under custody or control any firearm is guilty of a felony.
Unloaded open carry
For a very special circumstance, the ban on unloaded open carry at PC 26350 exempts unloaded 'antique firearms' through PC 16520(d)(5).