What impact? You'd have to police ALL your brass at any range, or Mistah Gangsta could scoop up your brass and toss it out the window of a drive-by, while they have a brasscatcher on their own gun. Then you get the no-knock raid.
Secondly, CA will suffer the same sort of "machinegun price effect" that MA is currently experiencing on used guns. New guns not on the "OK list" can't be sold anymore, so old models that were in the state previous to the law command a premium price. It's not uncommon for people to literally pay twice bluebook rates for an old, used, shot-out Glock (they have to be at least pre-1998) because there aren't anymore. The supply of those is dwindling due to attrition, wear and hoarding of the last few pristine examples. The same will happen with any gun from a maker that refuses to make special models for CA, and I suspect that will be most makers, since it's not profitable for them to make all those changes to their tooling for one highly restricted region of sales. Would you?
And finally, it's only a short hop to further restrictions. After all, they can't have those old C&R guns like 1911s, lacking stamps, coming into the state anymore, can they? I'd expect bans on C&R semiautos next.