None of the gun control legislation under discussion in Congress would have prevented the purchase of weapons by shooters in a recent spate of firearms violence, including last week's massacre at a Texas church, gun control supporters and opponents agree.

People at both ends of the spectrum in the gun control debate say the provisions before a House-Senate conference committee would have done nothing to save the scores of people who died in those attacks.

In that string of violence, all of the killers had either bought their guns legally or found an easy way to get around state and federal laws. The provisions now on the table, from child-safety locks to stricter regulation of gun shows, would not have stopped the sales.

"The whole gun control debate is on the fringe of the problem," said Kristen Rand, director of federal policy at the Violence Policy Center, a gun control advocacy group. "You can't pretend by plugging loopholes here and there that you're going to have an effect on the crux of American gun violence."

John Velleco, a spokesman for Gun Owners of America, voiced a similar conclusion for different reasons.

"Not only would the provisions being discussed do nothing to prevent those shootings, neither do the thousands of gun laws on the books today," he said.

The Senate version of the juvenile justice bill would impose new restrictions on weapons sales by unlicensed dealers at gun shows, requiring them to conduct criminal background checks on buyers. It also would outlaw the import of ammunition clips of more than 10 bullets, require child safety locks on all new handguns and prohibit juveniles from obtaining assault weapons.

The House defeated a weaker package of gun control measures and passed its juvenile justice bill without any gun provisions. The two sides remain far apart on a compromise, raising doubts that any legislation will be enacted this year.

The deadlock reflects Americans' enduring ambivalence on the issue of federal regulation of gun ownership. Congress is up against another eternal problem: It is impossible to prevent a mentally unstable person who has legal access to guns from using them.

Federally licensed firearms traders must have customers fill out a government form that asks a series of questions, including whether they have "ever been adjudicated mentally defective" or "ever been committed to a mental institution."

An affirmative answer blocks the sale. But although several of the recent shooters were seeking psychiatric help, none would have been required to answer "yes" on the form.

Determining the mental health of a would-be buyer is a thorny problem, said Adam Eisgrau, chief lobbyist for the Center to Prevent Handgun Violence and Handgun Control. Providing federal authorities or gun dealers with mental health records, he said, raises "substantial privacy issues."

"But that's the kind of discussion we have to begin, in order to protect ourselves from people who are just like us one day and then monsters the next," he said.

The current effort to reduce gun violence began in April, after the shooting deaths of 14 students and a teacher at Columbine High School in Littleton, Colo.

The two teenage killers, Eric Harris and Dylan Klebold, obtained three of their four guns -- two shotguns and a rifle -- from Klebold's girlfriend, Robyn Anderson. Because she was 18 and had no criminal record, her purchase of those guns was legal; though if she served as a "straw purchaser" for Klebold, she violated federal law.

It is not known whether Anderson purchased the guns from a licensed or an unlicensed dealer, but in either case she would not have been affected by the pending legislation because she would have passed a criminal background check.

Another provision of the Senate bill would ban the sale or possession of assault weapons by anyone under 18. But neither the rifle nor the two shotguns used in the Littleton slayings fall into that category, and Harris had recently turned 18.

It was illegal for Klebold and Harris to possess the fourth gun, a TEC-DC9 semiautomatic pistol, because federal and Colorado laws bar minors from owning handguns.

Mark Manes, a Columbine graduate, bought the pistol legally at a gun show and then sold it to Harris and Klebold for $500. Manes pleaded guilty in August to supplying a weapon to a minor and faces up to 18 years in prison at his sentencing next month.

Benjamin Nathaniel Smith, the 21-year-old white supremacist who went on a shooting rampage through Illinois and Indiana in early July, bought his two guns from an unlicensed private dealer who was not required to conduct a background check. Earlier, a federally licensed trader refused to sell guns to Smith because a check showed he was under a court order to stay away from his wife.

But even the stronger Senate bill would not have prevented Smith from purchasing the gun from the private dealer, because the bill's background checks would be required only at gun shows.

In the case of Mark Barton, a distraught day trader in Atlanta who killed nine people before shooting himself in late July, all four of his handguns had been purchased legally, federal agents say. And because Barton had no criminal record, he could have bought more weapons any time before the shootings.

Buford Furrow Jr., who went on a rampage at a day-care center outside Los Angeles in August, also legally bought the seven guns in his arsenal. Furrow did not become ineligible to purchase firearms until last fall, after he assaulted an administrator at a psychiatric hospital. He served five months in jail, making him a felon ineligible under federal law to own a firearm. But police had never taken away the arms he had already accumulated.

Last week, after Larry Gene Ashbrook went on a shooting rampage in a Fort Worth Baptist church, law enforcement officials said he had legally purchased the two semiautomatic pistols he carried that night.

"It's extremely doubtful any particular set of laws is going to stop people willing to die in order to kill other people," said James Baker, chief lobbyist for the National Rifle Association.

Baker and other opponents of expanded gun control laws argue that police could do more to reduce firearm violence by enforcing existing laws, including prosecuting would-be gun buyers who fail background checks. In Furrow's case, Baker said, authorities should have taken away the guns he had in his possession after he became a felon.

Gun control supporters on Capitol Hill argue that, although the provisions under consideration would not have prevented the recent gun violence, they nevertheless would solve at least one serious problem: the ability of felons to buy handguns, without background checks, from unlicensed dealers at gun shows.

"Criminals can walk into gun shows today and buy semiautomatic weapons and other firearms," Rep. John Conyers Jr. (Mich.), ranking Democrat on the House Judiciary Committee and a member of the conference committee, said in a statement last week. "This is the madness we are trying to stop."

After the Texas shooting, Sen. Orrin G. Hatch (R-Utah), who chairs the Senate Judiciary Committee and the conference committee, vowed to finish work on the juvenile justice bill.

"This event, and others like it in recent months, have energized a well-deserved and beneficial debate about the criminal use of firearms," he said in a statement.

But congressional staffers make it clear that the two sides are far from agreement and that, even in a season of shootings, the bill could go down in a partisan fight.

"We're about to sink this public investment in juvenile justice over the definition of a gun show," said a Republican staffer. "It's nuts."

Researcher Alice Crites contributed to this report.