18 to possess, 21 to buy from a dealer.
18 for long gun, 21 for hand gun
18
The only way to do it legally is to have the Georgia resident send it to an FFL dealer in California, then take possession of it through that dealer. Georgia's definition of gun rights and California's do not go hand-in-hand, at all.
If you are not a felon, then the legal age is 21.
Hand gun - 21; long gun - 18
21 for hand gun 18 for long gun
21
21
21
21.
See the related link at the bottom of the page
With the approval of your parents, at any age. On your own, 18 for rifle/shotgun, 21 for handgun.