More than 175,000 military retiree-civil servants, ranging from former sergeants to generals and admirals, would take a $740 million pay cut if Congress buys budget proposals cleared Tuesday by the House Post Office and Civil Service Committee.

Metro Washington has the biggest chunk of military retirees who are now working as federal civilians. Many of them could lose several hundred dollars a month in compensation because of the pay-pension offset approved by the committee, as a compromise to give federal workers a bigger October pay raise, and save twice-yearly COL (cost of living) raises for government and military retirees.

There are 12,000 to 15,000 military retirees here who have taken second careers in government. Under present law, retired enlisted personnel and retired reserve officers are allowed to keep all of their military retirement pay and draw full salaries for their civil service jobs. Retired regular officers are subject to an offset formula which allows those who take federal civilian jobs to keep the first $5,999.44 of their military retirement pay, plus one half the remainder, when they join government as civilians.

Faced with an order from the House Budget Committee to trim $5.1 billion from federal pay-retirement programs, Democrats on the Post Office and Civil Service Committee voted various program changes, in military retirement and postal savings, rather than go along with Budget Committee recommendations that white collar workers get a 4.8 percent raise this October, and that retirees permanently give up one of the two COLs they get each year. The PO-CS Committee recommendations have gone back to the Budget Committee, which will present them, along with spending cuts in other areas, to the House later this month.

Democrats on the committee voted in favor of the compromise to save the COLs and give federal workers a 5.45 percent raise this October. The Senate Budget Committee and Senate Governmental Affairs Committee have agreed to the 4.8 percent pay raise figure, and to limit retirees to one inflation adjustment each year. The compromise has found favor with many feds and retirees, with the very vocal exception of military retirees who have taken second careers with Uncle Sam. All of them -- all but disabled retirees -- would lose a portion of their civilian federal salary if the House PO-CS plan is accepted by Senate-House conferees when they meet later to come up with a new lowered budget favored by the Reagan Administration.

Under the PO-CS Committee proposal, military retirees in government would be subject to the same offset that applies to retired federal workers rehired by government. The federal salary is reduced by the amount of their federal pension.

Most military retirees in government are with the Defense Department, the majority by the Air Force, Army and Navy, in that order. They range from the lowest-ranked enlisted retirees to a handful of generals and admirals now wearing civilian clothes. The majority are enlisted retirees who not draw both full pension and full federal salaries.

According to a 1975 survey of military retirees in government, the largest concentrations outside of the Defense Department were in the Veterans Administration, Department of Transportation, Treasury, General Services Administration, HEW (now split into the Departments of Education and of Health and Human Services), and the National Aeronautics and Space Administration. Washington was their favorite work site, but other large concentrations were in San Diego, with nearly 7,000 military retirees-turned civil servants, Norfolk, 4,233 and San Francisco.