By KEN GUGGENHEIM, Associated Press Writer

WASHINGTON (AP) - Four powerful machine guns the State Department reluctantly bought for drug-fighting helicopters in Colombia were pulled from service after they repeatedly malfunctioned and threw the aircraft off-balance. The U.S. embassy calls the weapons a "big disappointment." The Gau-19 Gatling guns, which the administration bought for a total of $2.1 million at the urging of key Republicans and Colombian police, are so expensive to operate they threaten to "eat up our budget ... faster than it could possibly chew up narco-terrorists," an embassy cable complained to the State Department last month. In addition, the weapons are "temperamental" and so heavy they "can tip the aircraft dangerously forward," said the cable that laid out problems with the weapons. The cable was obtained by The Associated Press.

Just months after being acquired from General Dynamics, the triple-barrel, .50-caliber guns were broken down and could not be used in the Black Hawk helicopters the United States provided to Colombia. The helicopters are used to transport Colombian antinarcotics police, who often face fire from heavily armed leftist guerrillas who protect cocaine laboratories and coca fields.

General Dynamics spokesman Kendell Pease said the guns would be fixed quickly, based on the findings of a team the company sent to Colombia this week.

The staffs of two key House Republican chairmen suggested the difficulties with the Gau-19 likely stem from faulty installation and misuse. The chairmen, Reps. Benjamin Gilman, R-N.Y., and Dan Burton, R-Ind., have been the leading advocates of the weapons and are urging that more be bought in the next fiscal year. Their aides say the Gau-19's rapid fire and large rounds are needed to penetrate Colombia's dense jungle.

"The other weapons tend to be just noisemakers that scare the crows away," said John Mackey, an aide to Gilman, chairman of the House International Relations Committee. Gilman and Burton, chairman of the House Government Reform Committee, have repeatedly criticized Clinton administration efforts in Colombia, accusing the State Department of trying to foist unsafe, outdated equipment on the Colombian National Police.

The questions about the Gau 19s come as the Clinton administration is considering what weapons to buy for 60 helicopters - Black Hawks and Hueys - included in a new $1.3 billion U.S. aid package to Colombia. State Department officials said the Gau-19 problems haven't been a major setback to counternarcotics efforts because the helicopters have been using other weapons.

The U.S. embassy's Narcotics Affairs Section in Bogota originally opposed the purchase of the Gau-19s because it didn't want "to be the guinea pig" for what the cable described as an "unproven item." The State Department, however, acquiesced to the wishes of the Colombian police and congressional staffers, said a senior department official who spoke on condition of anonymity. The Black Hawks were altered to accommodate the Gau-19 at an added cost of $541,000. Those alterations were approved by the helicopters' manufacturer, Sikorsky Aircraft Corp. The embassy cable said the weight of the guns and ammunition leave the helicopters off balance and the guns' electric control boxes frequently burned out. In addition, their 2,000-round-per-minute fire rate made them "incredibly expensive" given that the .50-caliber ammunition can cost up to $4 a round, the cable said.

Mackey said the expense is justified given the value of the helicopters they protect. "How would you ever explain it if a $15 million piece of equipment is shot down and a Colombian crew is killed because you don't have the right weapons system?" he said. He said the electrical problems may stem from the pairing of two different machine guns on helicopters: the Gau-19, using AC current, on one side and the smaller-caliber MK-44, using DC, on the other. He said that may also explain the balance problems.

A Sikorsky spokesman, William Tuttle, said the Black Hawks should be able to accommodate the Gau-19s. Pease of General Dynamics said the Colombian air force has bought 34 Gau-19s in recent years and hasn't had major problems. The air force guns were installed by General Dynamics; the police guns were installed by contractors not supervised by the company, he said.

The cable said that after the guns were acquired, General Dynamics "belatedly" informed the embassy that only ammunition manufactured after 1983 could be used. By then, State Department had already sent Colombia 7 million rounds of .50-caliber Korean War-era ammunition that the cable described as "quite serviceable." Pease said the restriction was stated in manuals provided before the weapons were purchased.

With the Gau-19s out of service, Colombian police have tried using older, single-barrel Gau-16 .50-caliber machine guns in addition to the MK-44s. The Gau-16s are more accurate, can use the old ammunition, and are small enough that a spare can be carried in the helicopter, the cable said.