WASHINGTON — The families of the 17 people killed at Marjory Stoneman Douglas High School are among the most powerful lobbyists in Washington right now.

Lawmakers from both parties are willing to rearrange their schedules for an in-person meeting with a group of people who have already successfully shepherded a gun bill through the Republican-controlled Florida Legislature that was opposed by the National Rifle Association.

But the Florida Legislature is a part-time body, bound by time constraints to pass bills within a few weeks. Congress is under no such pressure, so many bills that have strong support from both parties can still languish for years.

"We don't move as fast as Florida legislatures do," Florida Republican Sen. Marco Rubio said. "This Congress, with 500-something members, represents a vast and diverse country and as a result there are people in different parts of the country that have different views on these issues."

The families of the Parkland victims have varying beliefs about access to firearms. Some, like Fred Guttenberg, want to ban all assault-style weapons. Others, like Ryan Petty, are concerned that a debate about banning assault weapons will shift the conversation into a partisan fight where nothing gets accomplished.

Read more: Some Parkland survivors are underwhelmed by Florida's new gun bill

But the victims' families are united behind three bills in Washington, and they're pushing to get two of them passed before the March for Our Lives on Saturday. The families are discussing legislation through Slack, an instant messaging application that allows users to break different topics into channels of discussion.

"We're probably one-upping the kids on that," Petty said of the parents' use of technology. "We put a proposal in one of the channels and then discuss it. I've been the liaison this past week, so as I was speaking with [Sen. Orrin] Hatch, Rubio, [Sen. Mitch] McConnell's office, I posted the messages into our group."

Petty said the parents come together and read the various bills and proposals in Slack, then one of them will write a statement either in favor or against the proposal before a final vote. The families don't come out in favor or against something unless there's a consensus.

But he acknowledges lobbying for legislation in Washington is "absolutely tougher" than trying to pass bills in Tallahassee. The families are trying to pass the STOP School Violence Act, which provides funds for school safety and coordination between school districts and law enforcement, and the Fix NICS Act, which aims to improve the background check system for guns by penalizing federal agencies that fail to report records, and increases federal funding for reporting domestic violence records.

Read more: With help of Parkland survivor, Rubio and Nelson push school safety bill

They want both bills passed by the end of this week, when Congress is expected to finalize a broad spending bill that will include many pieces of legislation.

Congressman Ted Deutch was able to get the STOP School Violence Act through the House procedurally very quickly, Petty said, "but the Senate doesn't work that way. These bills can be brought to the Senate and debated indefinitely. The concern we've always had as families, we understand how the story goes and over time something else will capture the attention of the media. If we haven't gotten legislation passed, people move on, the conversation changes, the media attention changes, and families of the victims are left without much progress legislatively and we move on to the next mass shooting or the next school shooting."

Even though all of the parents haven't collectively associated with the March for Our Lives movement, the continued attention brought by liberal and conservative Parkland students to the gun debate has forced lawmakers to continue paying attention.

And while the National Rifle Association isn't opposed to either the STOP School Violence Act or the Fix NICS Act, there is at least one gun ownership interest group, the Gun Owners of America, that is urging its members to support the 18 remaining Republicans who haven't signed on to the Fix NICS Act.

"There are still almost 20 Republican senators who have not bowed their knees to the graven image of Fix NICS," the group said on its website. "All of the pro-gun Senators need to be encouraged." Both Florida senators, Rubio and Democrat Bill Nelson, have signed onto the bill.

If the parents are successful in getting Fix NICS signed into law they will have already helped move the bill much faster than it was originally going. Texas Sen. John Cornyn introduced the Fix NICS Act in November 2017, one week after the Sutherland Springs, Texas, church shooting. In that case, the man who killed 26 people should not have been able to legally purchase a gun because he had been convicted of domestic violence by an Air Force court-martial.

But Cornyn's bill wasn't brought up quickly for a vote because Utah Republican Sen. Mike Lee objected.

"I can't remember a time when parents who just put their kid in the ground had to become lobbyists," said Democratic state Rep. Jared Moskovitz, who represents Parkland in Tallahassee and who fiercely advocated for Democrats and Republicans in the state Legislature to put aside differences to pass a compromise gun bill. "While we are partisan, it is not as bad as we see in Washington, D.C. We have one lunchroom [in Tallahassee] so there is more of a personal bond. In Washington it's more of a team sport."

One component of the Florida gun bill that isn't being fast-tracked in Washington is a proposal that would raise the age to purchase all rifles from 18 to 21. Many Republicans are opposed, arguing that it takes away the Second Amendment rights of young people who want to hunt and protect themselves. Rubio has argued that there should be exceptions where young adults can buy bolt-action rifles and shotguns when they turn 18.

"The moving to 21 in Florida, politically, is an easier step," Nelson said.

Petty also said the parents are supporting a recently introduced bill by Iowa Republican Sen. Chuck Grassley that provides additional funding to National Threat Assessment Center for research that aims to prevent school violence, though that bill will not likely be part of the upcoming spending bill.

"Our approach has been to be less ideological and more pragmatic," Petty said. "We recognize the clock is ticking. It's got to get through the Senate and get it through the president's desk."

Read more: Families of Parkland victims write legislators: Vote 'Yes' on gun legislation