21 or Older for Handguns
Both Federal law and California law prohibit transfer of handguns to those under 21 years of age.
Federal Law restricts FFLs from delivery to under-21: US CODE 18 USC 922 (b)
(b) It shall be unlawful for any licensed importer, licensed manufacturer, licensed dealer, or licensed collector to sell or deliver— (1) any firearm or ammunition to any individual who the licensee knows or has reasonable cause to believe is less than eighteen years of age, and, if the firearm, or ammunition is other than a shotgun or rifle, or ammunition for a shotgun or rifle, to any individual who the licensee knows or has reasonable cause to believe is less than twenty-one years of age;
California Law restricts everyone: Penal Code 12072(a)(3)
(3)(A)No person, corporation, or firm shall sell, loan, or transfer a firearm to a minor, nor sell a handgun to an individual under 21 years of age. (B)Subparagraph (A) shall not apply to or affect those circumstances set forth in subdivision (p) of Section 12078.
Penal Code 12078(p) exempts
- (p)(2): loans from a non-parent, with conditions
- (p)(3): loans from a parent, with fewer conditions
- (p)(6): purchases of antiques
In this context, 'antiques' are defined and Federal law and referred to by California law: 18 USC 921(a)(16)
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.
And, 12078(c)(2) allows Intra-Family transfer to 18,19 and 20 year olds.