A loophole in federal law may let as many as hundreds of thousands of people obtain a firearm without completing a background check, according to a new report by Joshua Eaton at ThinkProgress.

Under current federal law, people who buy a gun from a licensed dealer have to go through a background check. The FBI has up to three days to complete this check. But if it doesn’t, gun dealers are allowed to sell the firearm anyway. Many sellers choose not to, but some do proceed with the sale even if a background check wasn’t completed.

ThinkProgress, which obtained data from the FBI, found the FBI in 2018 failed to complete 276,000 background checks within the three-day window. That’s around 3 percent of background checks, out of the more than 8.2 million in 2018 — which is typical, based on data going back to 2014.

The loophole allowed a self-described white supremacist to obtain the gun he used to kill nine people at a predominantly black church in Charleston, South Carolina, in 2015. He had admitted to drug possession prior to the gun purchase, which should have prohibited him from buying a gun — but the FBI couldn’t complete his background check in time, and the seller allowed him to buy a gun anyway.

The Democratic-controlled House of Representatives passed a bill last week that would close this gap in the law — known as the Charleston loophole — by extending the time allowed for a background check to 10 days, among other changes. The bill is not expected to get through the Senate, which is controlled by Republicans who are largely opposed to stricter gun laws.

The National Rifle Association opposed the bill, claiming “it would put law-abiding citizens who need a firearm for self-defense at risk by trapping them in an endless loop of delays.”

Democrats also passed a universal background checks bill, which would close a separate loophole that allows private sellers — someone who’s unlicensed to sell guns for a living — to sell a gun without running a background check. This loophole has let unlicensed people sell or give guns to family members, friends, and people they met over the internet or at a gun show without verifying that the person getting the gun doesn’t have a criminal record, mental health history, or some other factor that legally bars him from obtaining a firearm.

The universal background check bill is also not expected to make it through the Senate.

America has the weakest gun laws in the developed world, and the highest levels of gun ownership out of any country in the world. At the same time, a study published in JAMA last year found that the US’s civilian gun death rate is nearly four times that of Switzerland, five times that of Canada, 35 times that of the United Kingdom, and 53 times that of Japan. The research indicates these issues are linked: Where there are more guns, and where gun laws are weaker, there are more gun deaths, including homicides and suicides, after controlling for other variables that contribute to crime and violence.

The House bills could start to strengthen these gun laws and address the US’s high levels of gun violence. But so far, they seem unlikely to get anywhere.

For more on America’s gun problem, read Vox’s explainer.