About 1,700 convicted U.S. felons and others barred from owning firearms have been able to buy guns since November because of problems with the FBI's new system of "instant" background checks, according to federal law enforcement records.

Federal authorities said the illegal purchases were the result of flaws in the FBI's National Instant Criminal Background Check System, which, as mandated by Congress, went into effect Nov. 30. The FBI said the background checks didn't link the buyers with their criminal records until after they were sold guns.

Under the instant-check system, the FBI has three business days to run a required background check for gun purchases. Although most sales are approved or denied within hours, gun dealers are free to hand over firearms to buyers if the FBI does not complete the checks within three days.

The bungled federal background checks are similar to problems experienced recently in Maryland, where, from December to early March, 49 handguns were sold to convicted criminals and others who are prohibited from buying them, after Maryland State Police fell weeks behind in completing background checks.

The FBI said it issued 1,687 "gun retrieval notices" from Nov. 30 to June 15 after guns were sold to criminals and other ineligible buyers because checks were not completed within the three-day waiting period.

The retrieval notices were sent to the U.S. Bureau of Alcohol, Tobacco and Firearms, which is responsible for tracking down and confiscating guns that shouldn't have been sold. Officials said they could not provide a breakdown of states where the guns were sold.

ATF spokesman John D'Angelo said yesterday he didn't know how many of the firearms have actually been recovered, adding, "We give these cases top priority in terms of investigations." ATF officials also said they did not know of any instances in which the illegally obtained guns were used to commit crimes.

But ATF agents said that in some cases, they discovered that criminals who were able to buy guns because of botched background checks also had dozens of other firearms in their possession.

For instance, on June 9, ATF agents searched a home on Maryland's Eastern Shore to recover a shotgun that was sold to a Talbot County resident who had been convicted of battery in 1994. A search of the home turned up 33 other firearms that were being kept illegally in addition to the shotgun, according to the ATF.

Matthew W. Horace, resident agent in charge of the ATF's Hyattsville field office, said his agents have seized a total of 103 firearms from eight people whose criminal histories were not detected in a timely manner by federal background checks. The Hyattsville office covers only the Eastern Shore, Southern Maryland and Montgomery and Prince George's counties.

"The trail is leading to many more guns than even we thought," Horace said.

Other ATF agents in Maryland have executed four search warrants to recover four guns and found a total of 12 firearms.

Because of an interlocking quilt of federal and state gun laws, the FBI conducts background checks on slightly less than half of all firearms purchases in the country.

The FBI performs background checks for all gun sales in 24 states. Fifteen states, including Virginia, run their own checks on all firearm purchases. Eleven states, including Maryland, conduct their own checks for handgun purchases or permits but rely on the FBI to screen sales of rifles and shotguns. Firearms sales are essentially banned in the District.

FBI spokesman Paul Bresson said the 1,687 illegal purchases represent only a tiny fraction of the 2.2 million background checks conducted by the FBI since the instant-check system began. "It's a small number, but on its face value it sounds like a lot," he said.

Congress authorized the instant-check system when it passed the Brady Act in 1993, but it gave the Justice Department five years to assemble the comprehensive criminal databases needed for its operation. Since the instant-check system went into effect Nov. 30, the FBI has denied more than 47,000 gun applications, Bresson said.

Most of the criminals who were able to purchase guns slipped through the checking process because the three-day waiting period did not allow enough time to determine whether the buyer was eligible, Bresson said.

The instant-check system has computerized access to more than 36 million criminal records, the bulk of which are provided by state court systems. In some instances, however, the state records show only that a person was charged with a crime -- which does not necessarily bar someone from owning a gun -- and do not indicate whether there was a conviction.

In those cases, the FBI must contact individual states directly to sort things out, a process that can take several days. "We're only as good as the information the states provide to us," Bresson said.

ATF agents in Maryland have received 34 gun retrieval notices from the FBI since Nov. 30 to seize rifles and shotguns that were bought illegally in the state, said Mike Campbell, spokesman for the ATF's Baltimore division.

Upon further review, two purchasers turned out to be eligible to possess firearms. Most of the other buyers voluntarily gave up their weapons after they were contacted by law-enforcement agents, Campbell said. A total of 12 search warrants have been executed in the state, Campbell said.

On May 27, a search in Calvert County turned up 22 guns, including a Chinese-made SKS 7.62mm semiautomatic rifle, an Olympic .223-caliber rifle and 10 handguns, according to court documents. On May 19, agents searched a home in Forestville for a $65 rifle that had been sold to a Prince George's County man who had been convicted of drug possession; they also found 26 other weapons, including shotguns and handguns.

ATF officials declined to name the gun buyers targeted in the raids or to give other details, saying that the cases are still under investigation. They said they are trying to trace the additional firearms that were seized to determine whether they had been used in any crimes.

The people who obtained the guns illegally face charges that they lied on their background-check forms by stating that they were not prohibited from owning firearms. So far, federal prosecutors in Maryland have indicted at least two people on such charges.

One of those indicted, Mark Holt, 37, of the 1500 block of Madison Street in Hyattsville, pleaded guilty June 1 in U.S. District Court in Greenbelt to being a felon in possession of a firearm and making a false statement in connection with acquisition of a firearm. He is scheduled to be sentenced Aug. 17.

According to an affidavit filed by an ATF agent, Holt bought a Mossberg Model 500A 12-gauge shotgun from a College Park pawnshop in early February. Before the three-day waiting period expired, an FBI background check failed to discover that Holt was the subject of a protective order signed by a Prince George's County judge after his live-in girlfriend complained that he had physically abused her.

The protective order stated that Holt was barred from possessing a firearm while it was in effect. Federal court records also show that Holt is a twice-convicted felon who served nine years in prison for attempted rape and robbery, and that he was diagnosed with schizophrenia in 1989.

Some people who were able to buy long guns in Maryland because of the incomplete background checks said they didn't realize their criminal pasts disqualified them from owning firearms.

Paul I. Brawner, 37, of Upper Hill, Md., said he paid $50 for a .22-caliber semiautomatic rifle at a Princess Anne pawnshop in January and filled out the background check forms. He said he didn't think his conviction in the mid-1980s, for second-degree assault for slapping his girlfriend, made him ineligible. When the three-day waiting period passed without a response from the FBI, he said, he figured there were no problems, so he picked up the gun.

ATF agents searched Brawner's home May 10 to recover the rifle. They also found shotgun ammunition and cocaine. He was charged in state court with possession of cocaine and drug paraphernalia.

"It's a bummer," said Brawner, an ex-Marine who blamed his nephew for bringing the cocaine and the paraphernalia into his home. "It's not like I'm a drug dealer or anything. I was just minding my own business in my own home. If the feds had just done their job to begin with, none of this would have happened."

Staff writer Lyndsey Layton and researcher Bobbye Pratt contributed to this report.

CAPTION: ATF agent Matthew W. Horace displays guns seized in Maryland.