When he heard about Oklahoma City, Richard Riley knew that accusing eyes would scrutinize the National Rifle Association for evidence that it bore responsibility for fomenting the hatred and paranoia that fostered the attack. And he believed the gun group would have a hard time justifying some of its recent activities.

None of which would be peculiar if Riley weren't a past president of the 3.4 million-member group.

"It's scary," says the retired firearms dealer, NRA president from 1990 to 1992. "We were akin to the Boy Scouts of America . . . and now we're cast with the Nazis, the skinheads and the Ku Klux Klan." The worst part, he says, is that the organization must accept its share of the blame -- though he thinks most of it rests with two people.

The bomb that ripped apart the federal building in Oklahoma City April 19 has also blasted open a schism in the nation's most influential association of gun owners. Old-line members -- who see themselves as conservationists and standard-setters in shooting competitions -- have fought a losing battle to regain control from Second Amendment "fundamentalists" who are focusing exclusively on gun legislation.

Leading that charge is the tag team that insiders say wields the real power at the NRA: board member Neal Knox and Tanya Metaksa, the organization's top lobbyist. Both have fought their way to control after being ousted from the NRA in the early '80s because they were considered too aggressive.

For the NRA's critics from within, the tragedy in Oklahoma City only deepens their fears that under Knox and Metaksa, the organization has become too strident. They are alarmed by materials like an NRA ad that referred to federal agents as "armed terrorists . . . clad in ninja black," or the fund-raising letter that warned of government forces destroying the American economy and culture. "You can see it when jack-booted government thugs, wearing black, armed to the teeth, break down a door, open fire with an automatic weapon, and kill or maim law-abiding citizens," the letter said.

And then there are the computer bulletin boards that link all manner of gun aficionados: Gun-Talk, open only to NRA members, and Bullet'N Board, operated by Metaksa and available to the public. Members like Riley were appalled to hear that one Bullet'N Board posting gave detailed directions -- including a diagram -- on how to construct a bomb.

On March 23, the NRA put a posting on the members-only bulletin board calling attention to rumors of "pending raids by the federal government on citizen militia units." Also posted was the text of a letter from NRA public relations director Thomas Wyld to the federal Bureau of Alcohol, Tobacco and Firearms, expressing the hope that the rumored raids were "fiction" and urging the bureau to contact a radio talk show host in San Francisco to dispel those reports.

According to two sources close to the NRA, there have been internal discussions for some months over the embarrassment that could result if the organization were perceived to be linked even peripherally to the paramilitary "militia" movement. According to Riley, NRA President Thomas Washington sent a memo last summer to the 75-member board cautioning that the association must avoid entanglements with such groups. Washington, who did not return calls about the memo, lives in Michigan, home to some of the most active militias. To some NRA members, his warning was prescient -- but it was ignored. Wayne Is the Softy Now'

Nominally, at least, Executive Vice President Wayne LaPierre is the top-ranking executive at the NRA, and he is the designated spokesman on all queries related to the Oklahoma bombing. He did not make himself available for this story.

Josh Sugarmann, a gun control activist and avowed NRA enemy, says LaPierre has been eclipsed by Knox and Metaksa. "He's the Ringo Starr of the NRA -- right place, right time," Sugarmann says.

A longtime NRA insider, intimately familiar with its political activities, says the landscape has changed for LaPierre, who used to be considered the aggressive one. "Tanya and Neal are hard-asses," he says. "They believe and they're zealots. . . . Wayne is the softy now. He's trying to keep them in their cages. They might throw him out of there."

As the organization's top executive, LaPierre is considered by some, as one source said, "a much more astute observer of the political landscape than {Knox and Metaksa} are. . . . In the face of this overwhelming issue {of Oklahoma City}, he is trying to be more Wayne and less them."

In the wake of congressional and other criticism of the NRA following the bombing, LaPierre said last week that the organization's rhetoric has been "strong and overblown sometimes," though he added that alleged abuses by federal law enforcement officials must be investigated "if we're to get a handle on the paranoia that's sweeping the country, especially in the gun ranks." Knox's View

Knox, 59, says the NRA's rhetoric is no worse than attacks that have been leveled at it. "I could cite quotes from members of Congress, newspaper editorials, cartoonists like Herblock, continuously doing that kind of thing to us," he says.

And he bristles at the idea that the NRA has not done enough to distance itself from militia groups. "Unless those people have committed a violation of the law, I'm not going to say we can't have anything to do with those people," he says. He believes there has been an orchestrated effort to discredit militia groups by linking them unfairly to the bombing.

From his home in Silver Spring, Knox runs an advocacy group called the Firearms Coalition but declines to estimate its membership. He also publishes a newsletter called "Hard Corps" and writes columns for other publications. His language is not staid.

In the Dec. 1, 1994, issue of Shotgun News, for example, Knox wrote a column suggesting that the assassinations of John and Robert Kennedy and Martin Luther King Jr., the 1989 schoolyard shootings in Stockton, Calif., and a few other massacres could have been the products of an anti-gun conspiracy.

Relating each event to contemporaneous efforts to pass gun control legislation, Knox wrote: "Is it possible that some of those incidents could have been created for the purpose of disarming the people of the free world? With drugs and evil intent, it's possible. Rampant paranoia on my part? Maybe. But there have been far too many coincidences to ignore." Knox says he stands by the column.

Knox argues that the NRA's queries about a possible federal raid on the militias were justified in the wake of the government's conduct at the Branch Davidian compound at Waco, Tex., two years ago and its attack on white separatist Randy Weaver. "When you have that kind of thing going on, don't you think that we ought to be cautious?" he asks. "There were intelligence sources coming in . . . that it might be true."

The only point that Knox concedes to his adversaries concerns the NRA computer bulletin boards. Despite First Amendment concerns, Knox says greater efforts may be made to monitor postings. But he adds that similar information -- including bomb recipes -- is available on other computer services.

He also dismisses as "nonsense" the idea that he runs the NRA.

"When there is an effort to demonize an organization it helps to put a face on it and they chose me," he says. Metaksa's Power

NRA insiders describe Metaksa as Knox's alter ego. The 58-year-old Smith College graduate has devoted most of her working life to guns. In spelling her name for reporters, she has been known to explain, "It's AK,' as in AK-47,' and SA,' as in semiautomatic.' "

She cofounded the Connecticut Sportsmen's Alliance in 1969 before going to work for the NRA in 1976, eventually becoming its chief lobbyist. But Harlon Carter, then the top executive at the NRA, pushed her out in 1980. She denied reports that she had alienated Sen. Robert Dole (R-Kan.) by threatening him with defeat if he didn't side with her in opposing a judicial nomination.

After leaving the NRA, Metaksa became chairwoman of Sportsmen and Conservationists for Reagan-Bush and then worked on Al D'Amato's Senate campaign. She became legislative director to the New York Republican and subsequently started a computer firm called Bullet Communications.

Since her return to the NRA, she has stirred controversy again, and not just because of her style. Some members objected, for example, when her company was given a contract to develop the Gun-Talk bulletin board without competitive bidding. When the contract was awarded, Metaksa was a member of the organization's board, though she has subsequently resigned. "I don't think anyone would think it was a big deal unless they were scraping the bottom of the barrel," Knox says.

To her supporters, Metaksa is a heroine. "Tanya has brought the NRA from this time last year, when we were being laughed at as a joke . . . to where in about eight months, we had the president of the United States blasting the NRA for having caused the upheaval and the Republican takeover of Congress," Knox says. "She has moved the NRA to a major player, and anybody that can do that must be doing something right."

But Dave Edmondson, a retired engineer and NRA board member from 1986 to 1992, says Metaksa is "abrupt to the point of being rude" -- and destructively uncompromising. Even some friends on Capitol Hill are distancing themselves.

The group broke with Rep. John Dingell (D-Mich.) over the crime bill. And Rep. Bill Brewster (D-Okla.), who has been an NRA member since 1973, has decided not to seek reelection to the board. Brewster says he could not attend enough meetings, but a source who has discussed the matter with him says he is not comfortable with the NRA's direction. Brewster acknowledges that some of the language in NRA materials sounds as if it goes "a little too far." Money Matters The NRA has another problem that insiders hang on Knox and Metaksa: money. Edmondson says they've driven the organization to the verge of bankruptcy. A balance sheet from August 1994 shows that liabilities exceeded assets by more than $55 million. Knox concedes that the organization's finances have taken a hit but says expenditures were necessary to build membership and upgrade the NRA's office systems after neglect by previous officials.

In fact, membership has swelled by nearly 1 million members to 3.4 million in the past four years. But Edmondson says the cost has been devastating. He estimates that the organization has spent $162 to attract each new member, while members pay only $35 a year in dues. With the NRA retaining only 20 percent of new members after a year, he says, the organization is in the worst financial crisis of its 125-year history.

Knox says a growing membership gives the NRA its most valuable asset: political clout. From all appearances, Knox is about to seal his own clout within the organization. Despite Edmondson's best efforts at leading a dissident movement, Knox and his forces are poised to unseat Washington, the portly president and head of the Michigan United Conservation League, at the NRA's May 19 meeting in Phoenix.

They are pushing Marion Hammer, a diminutive 56-year-old gun activist from Florida. She created the NRA's Eddie Eagle, a program that uses a cartoon character to discourage grade school kids from playing with guns.

"Marion's a doer," says a source close to the organization. "She's a woman. And people may listen to a woman more than some overweight guy." According to Edmondson, a plan is also afoot to replace LaPierre with Metaksa at the meeting. Edmondson's effort to seat a bloc of his own directors appears to have failed. "I just have a feeling that it's over," he says. "Turn out the lights." Knox, he says, will reduce the NRA to "rubble."

But Knox says there is no cause for mourning. The NRA is a democratically run organization and his slate represents the views of its members, he contends. "The NRA is 3 1/2 million people who care deeply about this country," he says. "We aren't in total agreement about everything, but we are a responsible group." CAPTION: Lobbyist Tanya Metaksa and past president Richard Riley, on opposing sides in the National Rifle Association's internal war.