Federal workers and military personnel who have averaged annual pay raises of about 6 per cent a year during the 1970s will probably get less this October when the next catch-up-with-industry increase is due.

Locally, about 400,000 white-collar civil servants and members of the armed forces get those annual October increases.

This year, however, the Carter administration wants government, industry and labor to observe voluntary wage-price controls. Controlling the government payroll - where each 1 per cent increase costs an additional $500 million - will be an important part of the President's voluntary program.

Under the law, government workers are supposed to get raises each October to make their pay "comparable" with private industry. The law gives the President almost unlimited leeway in determining what amount is "comparable."

President Carter won't make a final determination on the amount of the federal-military pay raise until he has studied comparative private wage data now being gathered by the Bureau of Labor Statistics. The BLS data, which will reflect private industry wages as of March, 1978, will be out sometime in July.

The President, in his campaign, promised to support the principle of "comparability" between government and industry. And federal union leaders have been reassured recently that Carter plans to stick with comparability. The interesting point, of course, is that comparability is pretty much what the president decides it is. And this year, experts are guessing, it could mean a raise of less than 6 per cent for government workers.

President Carter's formula for wage-price restraints asks that labor, industry and government hold 1978 increases "below the average increases of the last two years."

White-collar federal workers (and the military) got a 7.05 per cent raise in October of 1977. In 1976 they got sliding scale increases that averaged 4.8 per cent. If the President applies his guidelines to government workers, it would mean the 1978 boost could not exceed the 1976-77 average of 5.9 per cent. And it could be less than that, but no more.

Insiders caution that it is too early to be putting an amount, or a price tag (a 5.9 per cent raise would cost almost $300 million) on the October, 1978 raise. Key White House aides say the plan is to "decelerate" or slow the growth of federal pay, beginning this year. They talk about other factors, like "inflation distoriton" that could cause the 2-year average guidelines to be bent for the bureaucracy.

An important factor in the amount of the 1978 federal-military pay raise is that members of Congress will get it, too. And 1978 is an election year and politicians don't like to face the voters after hitting them for a pay raise.

If the President wanted to strengthen his "voluntary" wage-price program, he could present Congress with a relatively low October federal-military pay increase. Congress, under the political gun, would be hardpressed to argue for a higher "comparability" figure since members are among the beneficiaries.

The President's budget which goes to Congress Monday may spell out his 1978 federal-military pay plans. It will carry proposals for financing the increases but they are normally just estimates, and don't necessarily reflect what the final amount will be.

It is safe to speculate, however, that federal-military people in 1978 will be very, very lucky to get 6 per cent. It is almost as good a bet they will get less than that, particularly if the President feels he needs to set an example for industry and labor by volunteering the government to take the first step.