Defense Department brass -- generals, admirals, and senior civil servants -- are hoping to persuade Secretary Caspar Weinberger to become the point man in the battle to upgrade salaries of government executives and military personnel.

They want Weinberger to make the case, to President Reagan, Congress and the public, that sophisticated military weapons and programs are only as good as the officers and bureaucrats who operate them -- and that those experts are leaving government at an alarming rate.

Rank-and-file federal workers got a 4.8 percent raise last month, boosting the average white collar government worker here to $26,000 a year. Most military personnel got even larger increases. Top military and civilian bosses, who have been frozen at the $50,000 level for several years, were left out.

Language that limits federal-military career pay at the $50,112.50 level is attached to the continuing resolution financing operations of agencies without approved budgets. The resolution expires Nov. 20. A new one will be needed to keep agencies operating, and pay raise backers hope it is approved with a new, higher pay ceiling for U.S. officials.

The problem is partly fiscal, but mostly political. The average member of Congress would rather have skunk replace bean soup on the Capitol Hill dining room menu than have to deal with top federal pay raises.

House leaders -- Democrats and Republicans -- generally favor pay raises for frozen federal and military leaders, provided members of Congress (who make around $60,000 a year) get a raise of around 4.8 percent themselves. But the Senate, which recently raised outside income limits for itself, doesn't want any part of a federal-military pay raise that includes members of Congress. Sen. Ted Stevens (R-Alaska) is pushing a bill that would give military-civilian brass graduated pay raises lifting some to around $57,500, but without any increases for members of Congress.

Pay raise backers believe that Weinberger, perhaps Reagan's favorite cabinet member, is the man to sell the raises based on national security needs. Pentagon brass have worked up this set of statistics they hope will impress Weinberger, and the president:

* Because of the pay freeze, which also has an impact on retirement benefits, the Navy last year lost 20 percent of its senior executive corps.

* Four of every 10 top Navy civilian executives are eligible to retire now.

* The retirement rate of Navy civilian executives, which was 17 percent in 1978, is skyrocketing. Last year 95 percent of Navy's executives (many in key research and development programs) retired when they became eligible.

* Seven of every 10 top Defense Department civilian executives are in the highly technical R&D fields, which command big bucks in the private sector, especially now that Defense spending is increasing.

* Half of the Navy and Marine Corps general officers are now "capped" at $50,112.50 per year and by next year nearly all will be earning the same salary as junior officers and bureaucrats down to the Grade 15 level.

* If the freeze continues, every long-service (22 years) colonel and captain -- the backbone of the military establishment -- will be at the pay ceiling by 1984 and more than 4,000 of them will be eligible to retire.

Senior Executive Association president Jerry Shaw says he has been assured by House Speaker Thomas P. O'Neill (D-Mass.) that the leadership supports pay raises, but it needs bipartisan support and, most of all, words of encouragement from 1600 Pennsylvania Ave.