Washington — As Congress wrestles with a nearly $300 billion defense budget for 1985, the major issues are not so much weapons systems and how American forces are structured - or even dollars and cents - but arms control and Pentagon management.
The House has passed a number of important budget amendments that would limit several Reagan initiatives in conventional, nuclear, and space-based military assets. These include sea-launched cruise missiles, chemical weapons, antisatellite weapons, ballistic missile defenses, and that most obvious symbol of administration efforts to rearm America, the controversial MX missile.
All of these have much to do with critical arms control questions overshadowing cost considerations of lesser significance. Lawmakers also are considering changes in Defense Department cost estimating and restrictions on spare-parts purchases.
Administration officials say $436 hammers and other recent ''horror stories'' are the result of their own probing, and they insist that internal reforms already begun will solve the problem. But findings of internal audits and congressional investigators indicate that, after more than three years in office , the Reagan administration has only begun to sweep the Pentagon of wasteful practices.
Most of the pressure is coming from the Democratically-controlled House, which last week passed its defense authorization bill for the coming fiscal year. But in the Republican-dominated Senate (which takes up its version of the bill this week) there also are trends the Reagan administration does not find pleasing.
The General Accounting Office recently reported on Defense Department weapons cost estimates, and Sen. William V. Roth Jr. (R) of Delaware pronounced himself ''truly concerned and outraged'' by the GAO findings.
''The historic pattern of substantially underestimating weapons costs appears to be continuing, and cost growth is as far from being under control as it has ever been,'' charged Senator Roth, chairman of the Senate Governmental Affairs Committee.
Pentagon officials assert that weapons-acquisition reforms undertaken by the Reagan administration will help alleviate cost overruns. And they say another prime target of Pentagon critics - high-priced spare parts - should eventually be a thing of the past because of changes recently instituted.
Defense officials last week released what the Pentagon termed the largest audit in its history. The department's inspector-general found that 53 percent of those parts audited were overpriced or at least had the potential for costing too much because of lack of competition. But the independent watchdog (and another study by White House budget officials) also declared that management reforms outlined 18 months ago by Defense Secretary Caspar W. Weinberger will ''properly correct the causes of unreasonable prices.''
Lawmakers are not so sure. As part of its defense spending bill, the House is demanding more competition in spare-parts buying and would limit overhead costs charged to the government by defense contractors. Roth and other cost-conscious Republicans in the Senate are pushing for such changes as well.
On arms control, there is less unanimity between House and Senate. But at least some restrictive measures are likely to emerge as the two chambers work out their differences.
The administration had wanted 40 new MX missiles for 1985. The Senate Armed Services Committee cut this to 21. The House further reduced the number to 15 and added a provision delaying production until next April. House members also retained the authority to decide whether to proceed with MX production based on progress in arms control.
The House also prohibited testing the new Air Force antisatellite rocket against a target in space as long as the Soviet Union refrains from doing so. Representatives required the administration to report on whether new strategic nuclear weapons - the small single-warhead ''midgetman'' missile, the more accurate Trident II submarine-launched ballistic missile, and the MX - would give the United States a first-strike capability. And they voted to halt deployment of sea-launched nuclear cruise missiles until a way is found to distinguish such missiles from their nonnuclear version.
The Navy plans to begin deploying nuclear-tipped cruise missiles this month. Arms controllers say such weapons - small, hard to verify, and easily placed on hundreds of submarines and surface ships - could be extremely destabilizing, particularly since both the US and the USSR already have deployed many conventional cruise missiles at sea.
In all, the House added at least a dozen amendments having to do with arms control to its defense authorization bill. Included is a provision mandating compliance with earlier strategic arms limitation treaties (SALTs I and II), another ordering the Pentagon to report on how it will make the submarine force more survivable, and a third seeking ways to reduce the likelihood that theater nuclear weapons would be used in the early moments of war in Europe.
''This has been an amazing session for arms control,'' said Rep. Les Aspin (D) of Wisconsin, a member of the House Armed Services Committee and chief negotiator between Congress and the administration over the fate of the MX.
Like the House, the Senate Armed Services Committee has voted to trim the Reagan administration's request for advanced strategic defenses against ballistic missile attack, but by a lesser amount.
This, along with the MX, nerve gas, and antisatellite weapons, will be the most contentious items when House and Senate work toward compromise on defense spending.