“The current system is not operating correctly now,” Keene said. “The government has not funded it, and it needs to be fixed. . . . I do think we get to a point where you’re getting nothing as a result of it. While it sounds good, it doesn’t work.”

At least one governor, Louisiana’s Bobby Jindal, recently acknowledged that problem and asked state lawmakers to allow Louisiana to report severely mentally ill residents to the database.

The National Instant Criminal Background Check System was created in the 1990s after a mentally unstable man who was trying to assassinate President Ronald Reagan in 1981 shot and wounded the president and his press secretary, James Brady. Licensed dealers run checks by phoning a call center or submitting information on a website after the purchasers fill out a form.

Ten categories of people are barred from owning guns – from felons and illegal immigrants to drug abusers and those with mental illnesses. Some states have added additional restrictions, such as age.

During the 10 years that ended in 2009, about 100 million background checks were processed, with about 1.9 million applications rejected. In 2010, 150,000 applications were denied out of more than 10.7 million, according to the Department of Justice.

President Barack Obama acknowledged problems with the system in January when he unveiled a series of legislative recommendations and executive actions to curb gun violence.

He instructed federal agencies to submit information, write regulations to lift legal barriers that prevent states from reporting data and increase incentives for states to share information. Obama also directed the attorney general to review laws on who’s prohibited from owning a gun.

Congress already required the government to do many of those same things in the wake of Virginia Tech, and there have been improvements.

At the time of the Virginia Tech shooting, only four states had required agencies to send mental health records to the database, according to a November 2011 report from Bloomberg’s group. After the shooting, 18 states required it. And four states that hadn’t permitted the information to be sent began to allow it.

The number of mental health records submitted by states from August 2010 to October 2011 rose 35 percent. Five states – Texas, Washington, California, Missouri and Virginia – increased their submissions by more than 20,000 records, the study said.

That led to an increase in the number of denials. In 2004, only 365 gun sales were declined for mental health reasons. In 2011 that number increased to 2,124, according to the FBI.

But the reporting still lags.

Besides the lack of mental health data from states and the federal government, 44 states had sent fewer than 10 drug abuse records each as of October 2011, the mayors’ report said. That’s even though a single failed drug test, drug-related arrest or drug use admission might disqualify a person from buying a gun. Only three federal agencies have submitted drug use information.

Meanwhile, only a fraction – about $50 million – of $875 million in federal grants has been sent to the states since it was allocated in 2009 to help them develop better background checks, according to a report last year by the Government Accountability Office, which investigates government programs for Congress.

Since Newtown, the Bureau of Alcohol, Tobacco, Firearms and Explosives has sent letters to licensed gun dealers across the nation about conducting checks on behalf of private sellers.

Bob Irwin, the longtime owner of The Gun Store, which boasts the largest gun range in Las Vegas, said the request prompted a host of questions, including who’d pay the $25 fee to conduct the check and who’d pay the sales tax on the gun, which the state of Nevada requires for a transfer between private parties.

“No one wants criminals to get guns, but the system is fraught with logistical problems,” Irwin said.

Vice President Joe Biden, who leads the White House effort to reduce gun violence, joined Virginia officials in late January to promote changes in background check laws to prevent the wrong people from obtaining guns.

“There are certain things we know. . . will diminish the prospects of . . . what happened at Virginia Tech, what happened at these other mass shootings including Newtown,” Biden said.

On the five-year anniversary of the Virginia Tech shooting, Virginia Gov. Bob McDonnell, a Republican who supports gun rights, sent a letter to his fellow governors urging them to submit more records to the system.

“I would encourage you to evaluate your state’s reporting of mental health and other critical information to NICS,” McDonnell said, “and take any required action relating to that reporting to prevent tragedies such as the shooting at Virginia Tech from happening again.”