It’s clear she has no idea how a semiautomatic works, here she tries to tie them to “machine guns.”

Via RCP:

CHRIS WALLACE: All right. We have a couple of minutes left, and I want to ask you a question and Congressman King a question.

Senator, reaction to the Boston bombings has spilled into other issues, including gun control. There are some conservatives who say — some conservatives who say that, when a million people in Boston were forced to stay in their homes, that a lot of those people — particularly in Watertown where they were going door to door and there was a real concern that this fellow might be on the loose, might break into their house, might take hostages — would people like to have guns?
SEN. DIANNE FEINSTEIN: Oh, some may have, yes. But if where you’re going is do they need an assault weapon? I don’t think so. As the vice president said —

WALLACE: Shouldn’t they have the right to decide whatever weapon they feel they need to protect themselves?

FEINSTEIN: Well, how about a machine gun then? We did away with machine guns because of how they’re used. I think we should do away with assault weapons because of how they’re used.

WALLACE: Semiautomatics, that’s the most popular rifle in America.

FEINSTEIN: And you could use a 12-gauge shotgun and have a good defensive effect. And there’s the element of surprise.

Now, you’ve got police all over the place in Watertown, so I don’t really think that this is applicable. I think there are people that want to make this argument, but 12-gauge shotgun, there are many weapons, 2,000-plus weapons that are available to people for choice without an assault weapon.