Firearm Purchases:
In order to purchase a firearm, you will need a valid California Drivers License or Identification Card; or a Military DOD card/orders. You will also need an FSC card, or a valid exemption, as well as a separate form of proof of residency.
Please see the DOJs website for a list of acceptable ‘proofs of residency.’
https://oag.ca.gov/firearms/dlrfaqs#13G