Assume you mean long guns. Every type of firearm manufactured after 1899 other than non-metallic muzzleloaders need to be registered. Some manufactured before 1963 don't have serial numbers but that's OK, the Attorney General just records them with no SN. I have an FFL type 03 license, C&R, used it a lot before coming to CA. CA does not recognize it at all. And here is a kicker. If you inherit firearms from your father, as my wife did, she needs to complete a gun safety exam before she can possess the firearms. In the meantime, she had to give the guns to an FFL, send the info in to the Attorney General, including death certificate, and then wait almost 1 year to hear back. Then go to the FFL, pass the fireams safety exam, go thru FBI background checks on each one, pay the FFL a transfer fee for the paperwork on each one, go home and wait 10 days, and then take possession of the guns.
If you do some research, you'll see that pellet rifles, all kinds, are going to be considered as firearms if they are a larger caliber than .22. There is also legislation being considered to put slingshots and pea shooters and darts into the same category as crossbows, that is, dangerous weapons that need to be regulated. Can't make this stuff up.