Jennifer Steinhauer

WASHINGTON: The universe of potential changes to federal gun laws seemed to shrink Wednesday during an occasionally fraught Senate hearing on gun violence as lawmakers and proponents of more gun rules tussled with gun-rights advocates over the availability of some types of weapons and ammunition. In the end, chances for a ban on assault weapons dimmed, and compromise seemed elusive.

The hearing, the first held by the Senate Judiciary Committee since the mass shooting last month in a Newtown, Conn., school, began on a poignant note as former Rep. Gabrielle Giffords, who was critically injured in a 2011 shooting, addressed the committee slowly but with passion, essentially begging them to come up with legislation to address gun violence.

“Too many children are dying,” she said to a packed, hushed hearing room. “Too many children.”

After Giffords’ brief testimony, the four-hour hearing quickly devolved into a litany of competing statistics and chilling anecdotes, laying bare the deep national divide between those who believe gun availability contributes to the nation’s most violent crimes and those who think it helps prevent them.

Wayne LaPierre, the chief executive of the National Rifle Association said he did not support the measure that appeared to be gaining the most support among both parties — enhanced background checks for gun buyers — raising the prospect that perhaps even modest changes to gun laws would be hard to accomplish.

“Universal background check, which sounds, whatever,” LaPierre said, “ends up being a universal federal nightmare imposed upon law-abiding people all over this country.”

LaPierre’s strong defense of existing guns laws, which he argued were poorly enforced, and his occasional pique were a contrast with Giffords’ husband, Mark Kelly, a gun-owning former Navy captain and a retired astronaut, who quietly pulled, bit by bit, at the arguments against stronger background checks, which he and Giffords seek.

“I’ve been shot at dozens of times,” Kelly said. “I would suspect that not many members of this panel, or even in this room, for that matter, have been in any kind of a firefight. It is — it is chaos. I think there are really some very effective things we can do. And one is, Senator, the background check. Let’s make it difficult for the criminals, the terrorists, and the mentally ill to get a gun.”

The greatest area of disagreement centered on the availability of so-called assault weapons, which some Democratic senators seek to ban, and restrictions of large-size magazines, which several Republican senators and their witnesses argued would endanger potential victims of crime and infringe on the rights of law-abiding Americans.

Giffords, who made her way through the hearing room slowly, sat next to her husband and slowly began her remarks.

“This is an important conversation for our children, for our communities,” Giffords said. “For Democrats and Republicans. Speaking is difficult, but I need to say something important. Violence is a big problem,” she continued.

“We must do something. It will be hard. But the time is now,” she said, emphasizing the last word. “You must act. Be bold. Be courageous. Americans are counting on you.”

With that, Giffords made her way quietly out of the room.