Story highlights Clinton praises Sanders for his "flip-flop" on gun control legislation

The FBI has not interviewed her yet about her private email server, Clinton tells Jake Tapper

(CNN) Hillary Clinton on Sunday sharpened her attacks on Bernie Sanders over the Vermont senator's record on gun control, just hours ahead of their fourth debate as both vie for the Democratic presidential nomination.

"I am very pleased that he flip-flopped on the immunity legislation," Clinton told CNN's Jake Tapper on "State of the Union," a day after Sanders, who had been hammered by her campaign for his past position, announced he would change course and back legislation to reverse a 2005 law granting firearm manufacturers legal immunity.

Gun loophole

She then called on her rival to do the same with the so-called "Charleston loophole," which allows licensed dealers, once they have initiated a federal background check, to complete the gun sale in question if they haven't hears back from authorities after three days.

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