Most of the 5,053 civilian employes who work at the China Lake Naval Weapons Center, a military base the size of Delaware, have been on the front lines of civil service old and new. On the whole, they prefer the new.

They are Exhibit A in a Navy demonstration project that the Office of Personnel Management (OPM) considers to be the most significant and successful test of new civil service rules ever conducted. Administration officials are so pleased with what has happened here that President Reagan last week proposed to expand the experiment to the entire federal work force.

What the Navy did here was to revamp the rules to give managers more flexibility and workers more incentives. The changes helped China Lake recruit and keep more and better-educated workers, raised average salaries and improved morale.

In 1979, China Lake was losing its highly trained scientists. With 85 vacancies, the center recruited only 35 replacements. Attracting engineers and technicians was tough at traditional GS (general schedule) levels that started a graduate scientist as low as $11,200 a year. The college grade-point averages of starting engineers and professionals had fallen to 2.7 on a scale rising to 4.0.

Last year, the base had 171 vacancies and filled them all. Starting salaries for scientists and engineers went to $24,701. Grade-point averages of new recruits have risen from 2.7 to 3.2. The average salary of scientists and engineers has gone up to more than $40,946 a year, compared with about $38,000 in control labs using the traditional civil service system. Turnover is down. The experiment cost about 5 percent more than the system it replaced.

OPM Director Constance Horner came here last week and described the proposal to make the China Lake experiment the standard in government as "so radical it is breathtaking."

"I believe the system we've got in place is so retrograde, so out of keeping with the national spirit, so alienating to the national work force that it is my intention to fix it," Horner said.

"Under the system I grew up with, the first-line supervisor could pass the buck. Now he has to make hard choices," said Burrell Hays, the recently retired technical director who ran the demonstration. "Productivity moves up, the weak person moves back. We get more efficient and effective use of personnel."

Electronics technician William Fretz agrees with Hays that the changes have improved conditions at China Lake. "I have good feelings about the demo," he said. "I have direct communication with my supervisor. I know what to expect. We have a deal: If I meet my goals I get rewarded. They tell me exactly what I can improve. It allows financial growth. I got promotions."

China Lake sits deep in the Mojave Desert, about 50 miles from Death Valley. The 5,053 civilian workers here have helped to build 80 percent of the weapons used in Vietnam and more recently in Libya. A self-contained operation, it had run into trouble by the late 1970s.

"It took over a year to get a job classified," said Eva Bien, head of the personnel department. "Managers were venting their frustrations on the personnel department in a screaming match . . . .

"People were being moved and the PDs [position descriptions] weren't being updated," a violation of civil service rules that could cheat an employe out of either a higher salary or credit for experience.

But the Civil Service Reform Act signed by President Carter in 1978 offered an opportunity for something new, authorizing merit pay experiments. China Lake and the Naval Ocean Systems Center in San Diego proposed a joint experiment.

"The employes were involved here right from the start. We built the system from the ground up. That's important," said Bob Glen, demonstration project manager. "Each layer put its own stamp on it," said Dr. Ed Royce, head of the research department at China Lake, so that employes would feel they had a say in the system.

Similar occupations were grouped together and GS levels were consolidated into broad "pay bands" encompassing from two to four GS levels in each band.

The point was to allow the Navy flexibility to offer more competitive starting salaries to engineers, and to allow salaries to rise with ability and experience without having to reclassify workers from one GS level to another, according to OPM.

At China Lake, raises, called increments, were based solely on performance under the experimental plan. The better the worker, the higher the pay.

Comparability pay -- pay raises awarded across-the-board to federal workers to keep their salaries in step with private industry -- and all the money that normally would go into in-step, or longevity increases, went into the merit pay pool. The pool at China Lake was roughly 2 1/2 percent of workers' salaries, plus whatever all federal workers got for comparability.

First-line supervisors sat down with workers at the beginning of the year and wrote a "performance plan." At the end of the year the supervisor assessed the worker's performance against the plan and awarded one of five ratings, from "substantially below fully successful" to "demonstrably exceptional." All workers rated above fully successful got an annual raise of two or more increments, worth between $400 and $1,000 at China Lake. Spectacularly successful workers received up to four increments. Workers rated less than fully successful got nothing.

Last year, when Reagan did not grant comparability pay because of the federal deficit, the pay pool was far smaller than workers expected when the demonstration began. This has led to considerable grousing because there was not enough money last year to give raises to some workers who were "fully successful" and doing a good job.

Among supervisors, to whom the demonstration gives tremendous new responsibility and authority, "I have seen some cowardice," said Johnson M. Johnson Jr., head of systems engineering at China Lake. "A branch head wants to be a good guy and recommends everybody for a highly successful rating, when, of course, he can't give everybody that. I've seen it happen once here, but the guy transferred" out of Johnson's division soon after.

Royce said that within his department ratings of "less than fully successful" have proved to be "extremely salutary things. Three times out of four they are not in that category again."

Union officials have questioned the experiment, which is similar to a highly controversial proposal made by former OPM director Donald J. Devine in 1983. They worry that the system will penalize workers who are good, but not sensational, as managers "rob Peter to pay Paul." The American Federation of Government Employes, in a statement issued Thursday, opposed the president's pay proposal as a "quick fix . . . not necessarily the solution to this complex problem."

Rep. Mary Rose Oakar (D-Ohio), whose subcommittee on compensation and employe benefits will hold hearings on the president's proposal, questions whether the China Lake demonstration can be transferred outside a remote desert weapons laboratory where morale and community spirit are high.

The demonstration project cost about 5 percent more than the system it replaced. Horner said that elsewhere in the government, where scientists' and engineers' salaries would not be such a large factor, this would not be true. The Office of Management and Budget initially opposed the program's expansion, however, as a disguised way of raising federal pay. OPM is drafting legislation requiring that the new system be "cost neutral."

But Horner said OPM has "to give federal managers responsibility and make them accountable for delivering for the American people." What she hopes to launch, she said, "is a mission of faith."