Something not yet mentioned in discussion about CA gun owners & voting...
It isn't only the numbers of gun owners voting that matters it is the geographical distribution of the voters that matters too.
I understand the concept of "gerrymandering" is alive and well in CA (CA residents, if I'm wrong on this, please speak up).
SO, even if you could get that entire 21.3% (1 in 5, essentially) to vote as a solid block, every time, it would only have an effect on issues where the entire state wide public gets a vote.
This situation of the CA gun laws comes from the people being put in the CA legislature, and those are elected not by the state as a whole, but by the residents of each district. SO, no matter what you do, you are going to get anti-gun politicians, and just as bad, politicians who don't care one way or the other, and see gun control as a useful prop for their personal agendas.
I think it possible that some CA politicians support these laws primarily because the worst thing that can happen to them, personally is that they upset the 1 in 5 voter who wasn't going to vote for them anyway...and in return for passing yet another "reasonable, common sense law" they get some concession or support from the hard line anti gunners on something that matter to them, personally...