There are a lot of reasons to gig President Obama about gun control, but saying he broke a promise about it isn't one of them. Like the "broken promises" stories about immigration reform and his failure to close the detention camp at Guantanamo, it's a distortion.
The truth is, he never promised to push for more gun restrictions. He took the namby-pamby politician's approach of saying more should be done, but he never really promised to do it himself.
It's understandable.
Gun control is an anaconda no one wants to wrestle. And, despite tragedies like the Aurora shooting, Virginia Tech and Columbine, the people of the United States generally resist the idea of gun control.
Still, the president has waded into this one a few times.