A bump stock at a gun shop in Raleigh, N.C. (Allen Breed/AP)

For the first time in recent history, a Republican-controlled Washington did something to limit people’s use of guns. Two things, actually.

Or you could look at it another way: The gun-related legislation attached to a spending bill that President Trump signed into law Friday is so modest that it merely reinforces existing law.

“There is a simmering sense in this country that much more needs to be done,” said Lindsay Nichols, with the gun-control group Giffords, “and this is not it.”

Here's what will change on guns just a month after the Parkland, Fla., shooting and a day before what is expected to be one of the largest marches in history to demand more gun-control measures. And below that, we break down what gun-control measures Congress probably won't enact anytime soon.

What Congress just did on guns

1. They voted to strengthen existing background checks: The most recent change to background checks came in 1993, when Congress instituted a federal background check system. But gun-control advocates say that that system is understaffed and underfunded, and there are ways to get around it by buying a gun at largely unregulated gun shows or online.

Enter a bipartisan bill that doesn't expand background checks, but does require state and federal agencies to add people's criminal records into the system in a modest effort to make it more expansive.

2. They opened the door to federal funding for gun violence research: For 20 years, federal government research on gun violence has more or less been prohibited. As my colleagues William Wan and Sean Sullivan point out, there was never an explicit ban, but in 1996, Congress supported a gun-lobby priority to say that no funds from the Centers for Disease Control and Prevention “may be used to advocate or promote gun control.” That had a chilling effect on all federal funding related to guns.

Congress took its first step this week to reversing that. It passed a measure that indicates that the CDC can research gun violence but said nothing about gun control. Advocates for the latter said they appreciate the small step toward opening up federal research on guns but called this a largely symbolic step that won't change much.

“There's not all of a sudden going to be this booming research coming out of CDC,” said Andrew Zucker, a spokesman for Everytown for Gun Safety.

3. They are moving to ban bump stocks: Actually, this isn't Congress's doing. Even though there's bipartisan support to ban the device that can make a legal semiautomatic weapon fire more like an illegal machine gun, Congress has left the decision-making to the federal agency that regulates firearms. That agency is caught in red tape about what it can do without a new law from Congress. But on the eve of the March for our Lives, Trump tried to bust through that red tape and announced the Justice Department would propose banning bump stocks. But it's still a ways to go to actually ban them.

What Congress probably won’t do anytime soon on guns

A semiautomatic rifle at right that has been fitted with a bump stock at a police station in Seattle. (Ted S. Warren/AP)

1. Raise the age from 18 to 21 to buy assault weapons: Republicans in Florida did this after it was revealed that the Parkland shooting suspect legally bought his assault weapon at age 19. Some Republicans in Congress want to do this. But most GOP lawmakers don't see a reason to break with the powerful National Rifle Association on this. They argue that raising the age limit would unfairly limit the rights of young, law-abiding gun owners.

2. Reinstate a ban on assault weapons: This is the top demand from gun-control advocates in the Parkland community. Congress banned the guns for a decade in 1994 but never reinstated the ban. Today, even some Republican lawmakers who seem open to modest gun-control measures don't support the ban or even heavy regulation of the guns.

3. Expand background checks: People who buy guns at gun shows and online can get around having to go through a background check.

After Parkland, Trump vaguely said he supports “comprehensive background checks,” but he hasn't elaborated on what that means, suggesting he might not be willing to push hard for it. And it's very unlikely Congress does anything on this, the Holy Grail of the gun-control community, without a sea change from within their own ranks.