My comments are accurate as of a few months ago when I last read the regs. Recall that there were two competing propositions on the ballot, one by Newsom and another with the same general direction but differing provisions. Since both were passed, the courts tried to sort out which would prevail and I don't know if the actual implementation has yet been clarified. As an example, one proposition prohibited bringing any ammo from out of state, the other prohibited bringing more than 50 rounds from out of state. Which is the actual law? Who knows? There was rather extensive discussion of potential border enforcement on some of the CA outdoor boards before the fall hunting seasons, but there was no consensus about what was legal, how it would be enforced, or even if it would be enforced. I was never checked on multiple trips back from AZ, but my FFL told me that his sources said someone had been nailed for "importing" ammo and was in a world of hurt because of it. Don't know the details, but this FFL is pretty reliable.
Re giving shells to your friend, when I read the regs they said you cannot "transfer" shells without involving an FFL or licensed ammo dealer. Giving your friend some shells is a transfer, so is it legal? May depend on who catches you doing it.
Re loaning a gun to you friend in the field, this is from the CA.gov website:
AB 1511, Santiago. Firearms: lending.
Existing law generally requires the loan of a firearm to be conducted through a licensed firearms dealer. A violation of this provision is a crime. Existing law exempts from this requirement a loan of a firearm between persons who are personally known to each other, if the loan is infrequent and does not exceed 30 days in duration.
This bill would instead limit that exemption to the loan of a firearm to a spouse or registered domestic partner, or to a parent, child, sibling, grandparent, or grandchild, related as specified. The bill would require a handgun loaned pursuant to these provisions to be registered to the person loaning the handgun. By expanding the application of an existing crime, this bill would impose a state-mandated local program.
So, as I read this, you could loan your friend a gun for brief periods under the old law, but now you can loan a gun only to someone who is related to you.
THE PEOPLE OF THE STATE OF CALIFORNIA DO ENACT AS FOLLOWS:
SECTION 1. Section 27880 of the Penal Code is amended to read:
27880. Section 27545 does not apply to the loan of a firearm if all of the following requirements are satisfied:
(a) The loan is to a spouse, registered domestic partner, or any of the following relations, whether by consanguinity, adoption, or steprelation:
(1) Parent.
(2) Child.
(3) Sibling.
(4) Grandparent.
(5) Grandchild.
(b) The loan is infrequent, as defined in Section 16730.
(c) The loan is for any lawful purpose.
(d) The loan does not exceed 30 days in duration.
https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=201520160AB1511This link is as of right now. I have seen no indication that the law has been modified since Brown signed it.