As of 2010 California suffers 56% more gun murders than Texas. Similarly, of all ways to murder people, Californians murder people with guns 69% of the time, while Texans murder with guns only 65% of the time. This indicates that the average Californian is more likely to murder or be murdered with a gun than the average Texan.
No-one knows for sure how many guns exist, are owned, and who owns them, but I did find a 2001 survey that purportedly broke down likely gun ownership by state. According to these numbers, Texans as a whole own 45% more guns than Californians. That’s total guns, not guns per capita. So it would seem that even with fewer total guns spread among more people, more are still murdered with guns in California.
If you break down the number of gun murders per 100,000 people, we see the likelihood of gun murder relative to the size of the population. This is the actual likelihood that you will be murdered with a gun in that state. With this measure, we see that your chance of murder by gun is 1 in 29,674 in California, compared to the less likely 1 in 31,348 in Texas.
Interestingly, the most violent gun crime area in America by far is Washington DC. No state comes anywhere close. There is almost an order of magnitude more gun murders in Washington DC than any state. Your chance of being murdered with a gun in Washington DC is 1 in 6,250. Washington DC is infamous for its long standing ban on legal gun ownership by private citizens, in direct violation of the Second Amendment. This ban was partially lifted a couple years ago, but the restrictions on private gun ownership are still severely limited.
At the other end of the spectrum, the city of Kennesaw, Georgia has had a city ordinance since 1982 requiring all households to own at least one gun and ammunition for it, with the reasonable exceptions of the mentally handicapped, religiously convicted against guns, and known criminals. Their overall crime rate is half the US average.