Barbara Boxer can read the polls, and she knows that even within California her extreme anti-gun positions gain her nothing (since she's already got the liberal vote locked up) and just energize her opponents. So she's found an issue on which she can agree with the pro-gun folks and she's running with it.
It's a smart political move. And she deserves our applause on this narrow issue. After all, that's how we have to shift the political calculus for politicians. We have to make it politically undesirable for them to oppose the Right to Keep and Bear Arms, and politically rewarding for them to support RKBA.
Given the right carrot-and-stick combination, we may be able to keep moving Boxer in our direction. She won't do so out of principles or conviction, but out of political expediency. That's still better than nothing. And she's going to be in the U.S. Senate for at least another six years, since Bill Jones has approximately zero chance of upsetting her.
I even remember Feinstein being one of the key speakers on the floor of the Senate vigorously arguing for passage. I thought something was wrong with my TV. This legislation was presented a short time after 9/11 when sentiment was strong. That's the only reason I can figure they got on board.