But in the month since, Congress has taken no action on bump stocks or any other gun-related matter. The committees with jurisdiction have held no public hearings. Following the NRA’s lead, Republicans called on the Department of Alcohol, Tobacco, Firearms, and Explosives to look into bump stocks rather than tackle the issue themselves.

In short, nothing much has happened, and the feedback that Charlie Dent received helps explain why.

Polls have consistently shown broad public backing for additional regulations on guns, including more than 90 percent support for universal background checks. But, as Dent told me, “one side has historically been more energized.” And while advocates for gun control often focus on the millions of dollars that the NRA spends on campaign contributions and TV ads as the biggest obstacle to congressional action, the group’s success may owe just as much to the army of grassroots activists that amplify its message to lawmakers.

“There’s a certain very vocal constituency of individuals who are convinced that at any moment, their gun is going to be ripped away from their hands by the federal government,” said Kris Brown, the co-president of the Brady Campaign to Prevent Gun Violence. “They will call, and they’ll call about just about anything that the NRA gets them worked up about.”

Though the NRA called for regulating (not banning) bump stocks after the Las Vegas shooting, it opposed action by Congress. Instead, it put the onus on the ATF to revisit a ruling it made during the Obama administration that the devices were not covered by either the Gun Control Act or the National Firearms Act. In turn, House Speaker Paul Ryan and other Republican leaders in Congress asked the ATF to look into the issue, effectively shelving the legislation Dent supported, which was introduced by Representative Carlos Curbelo, a Florida Republican, and Seth Moulton, a Massachusetts Democrat. The agency has yet to reply, Moulton told me.

“When they do is the time for [Ryan] to take up the legislation,” Moulton said.

It’s unlikely that Congress will move that quickly, if at all. In the House Judiciary Committee, Democrats have complained that Chairman Bob Goodlatte of Virginia, a conservative Republican, has denied their requests to hold hearings on gun violence. The same is true in the Senate. In a statement, Goodlatte said he has been in contact with ATF about bump stocks and that the bureau will be briefing members of the Judiciary Committee on the issue this week. “While there is still much to learn about what happened in Las Vegas, the use of bump stocks in that horrific tragedy is extremely concerning,” he said. “As chairman of the House Judiciary Committee, I am committed to looking at the regulations dealing with bump stocks to see if they need improving.”