WASHINGTON (AP) _ Slowly, deliberately, Richard Davis loads his .44-caliber Magnum handgun. He grasps the pistol with both hands, points it at his abdomen and stares ahead grimly. He fires; his body jerks with the impact.

A grin spreads across his ruddy, weather-beaten face. ''Nothing to it, folks,'' he says with the satisfaction of a man who has shot himself more than 130 times as a sales pitch for the bulletproof vests his company manufactures.

But despite Davis' confidence in his product, the federal government is pushing national standards for body armor that he and other producers consider unreasonable. The feud has become so bitter that some law enforcement groups, for whom vest quality is a life-or-death matter, are asking Congress to intervene.

Sen. Dennis DeConcini, D-Ariz., said he expects to introduce a bill to establish mandatory standards this month. Sen. Carl Levin, D-Mich., has written Attorney General Dick Thornburgh urging him to mediate a compromise. ''The increasing uncertainty can only hurt law enforcement officers,'' Levin wrote.

The highly technical debate boils down to four issues: how the vests should be designed, particularly the amount of stuffing needed to stop bullets; how they should be tested for effectiveness; who should set the standards; and whether they should be voluntary or mandatory.

The National Institute of Justice, a branch of the Justice Department, has set voluntary standards for vests and tested them for quality since the early 1970s.

During testing, vests are mounted on clay blocks and bullets are fired into them from varying distances and angles. To meet NIJ standards, a vest must not only stop bullets; it must also prevent them from making an excessively large dent in the clay. That's because a bullet can strike with enough force to damage internal organs even if it doesn't penetrate the vest.

The government toughened its standards in 1987 to keep pace with changes in weapons and ammunition, said Lester Shubin, science and technology director for the NIJ.

Suddenly, more than 50 percent of the vests were flunking the tests.

Manufacturers - including Davis' Second Chance Body Armor of Central Lake, Mich. - cried foul, saying the only way to ensure that their vests consistently passed was to make them so thick and bulky that police wouldn't wear them.

''Police officers don't really want to wear the stuff, anyway. Give them any excuse to take it off and they will,'' said Ed Bachner, ballistics manager for E.I. Du Pont de Nemours & Co. His company manufactures Kevlar, the synthetic fiber used in most bulletproof armor the past 20 years.

''Police are dying because they aren't wearing vests, not because the vests are bad,'' Bachner said.

Surveys show that only about 30 percent of police wear vests, even though many law enforcement agencies require it, said George Austin Jr., national executive officer of the Fraternal Order of Police. Manufacturers say the number may be lower.

Du Pont has documented more than 1,000 ''saves,'' or incidents in which wearing Kevlar body armor prevented death or serious injury, Bachner said. Most are shootings, but many have involved stabbings, auto accidents and even a couple of bull gorings.

A single vest retails for about $350, Davis says, although he recently sold 4,000 to the Detroit Police Department for $175 apiece.

Larry Gates, executive director of the Personal Protective Armor Association, an industry group, says no vest has ever failed to protect a wearer from bullets it was designed to stop.

''They've performed flawlessly in the field, where it counts,'' he said. ''But in the laboratory tests under the NIJ standards, over half the vests fail. The test is flawed ... but the NIJ won't budge.''

Shubin counters that vests have a good field record because his agency's tests have kept duds off the market.

''We believe a lot of their armor is marginal,'' he said. ''But we believe if it passes our standard it's going to work 100 percent on the street, and it has. We're being faulted for being successful.''

Last year, Du Pont and the Personal Protective Armor Association established their own standards, which they say produce more consistent test results while meeting wearers' comfort requirements.

Shubin and many police leaders aren't convinced.

''I could put up with a little discomfort in exchange for extra protection,'' said Austin, the FOP officer and a Poquoson, Va., beat cop. ''And I'm the one out there on the street getting shot at.''

Police generally have sided with the government in the dispute, although not unanimously.

New York City Police Commissioner Lee Brown, who favors the NIJ standards, calls the debate over vest design and testing procedures a ''smoke screen.''

''The issue is who's going to develop the standards,'' Brown said. ''I want them developed by someone who has no vested interest in selling a product.''

The Fraternal Order of Police wants Congress to designate a non-industry body such as the NIJ to set national standards, and the International Association of Chiefs of Police has taken a similar position.

But the State Association of Chiefs of Police, a division of IACP, voted last month to oppose congressional intervention and to ask the manufacturers and the NIJ to accept binding arbitration.

One vest manufacturer that supports the government standards is Point Blank Body Armor of Amityville, N.Y. Company president Richard Stone says the industry's primary motive is to protect Kevlar's dominance of the bulletproof vest market.

''This is basically a commercial situation,'' Stone said. ''Du Pont's had a virtual monopoly on body armor for 20 years and they want to keep it that way.''

Du Pont's Bachner disagrees, saying the controversy arose before the recent emergence of competing synthetic fibers. ''I tell police if they can find a better product they ought to buy it,'' he said.