Of the top 10 or so, some have high rates of gun crime and others don’t, so it’s obvious that their ratings don’t mean very much.
That's not really true. At least in the case of Kalifornia, the score is indicative of the additional hassle and expense of keeping and bearing arms, above and beyond actual prohibitions.
I have spent thousands to counter the unacceptable aspects of Kalifornia's so-called "Assault Weapons" laws. Only recently have I regained use of a two thousand dollar target rifle which had been outlawed by name and by irrelevant features some ten years ago.
Since some FFLs are intimidated by having to interpret unacceptably vague gun laws, I have to drive 240 miles every time I purchase a firearm (two round-trips to his location 60 miles from my home, separated by a meaningless ten-day-wait).
I still carry the Basic Firearms Safety Certificate issued by Kalifornia that was supposed to be good for life. I also carry two copies of the replacement Handgun Safety Certificate because the first one expired. Each certificate costs about $25 not including my time.
I carry these documents so that I can explain to anyone who needs educating what an infringement it is to require an Army veteran to periodically prove that he hasn't forgotten how to handle firearms safely.
For the record, I recently lost all my firearms in an unfortunate boating accident.