The drums are beating on Capitol Hill again as they did during much of the spring -- for a multibillion-dollar mortgage subsidy program to help home buyers and builders.

Legislation that would provide cut-rate loans of 8 1/2 and 9 percent to 140,000 new home buyers has been drafted by key House Democrats. This bill is similar to the bipartisan housing-assistance legislation passed by Congress in June, but was vetoed by President Reagan.

Since the new bill's price tag is $1 billion less than the earlier $3 billion version and its deep subsidies are all repayable to the Treasury, sponsors are hopeful about its future.

They plan to persuade majorities in both the House and Senate to pass it during the lame-duck session of Congress beginning Nov. 29 -- and to get thousands of buyers into houses with subsidized mortgages by the late spring.

They could succeed.

But if you're a potential home buyer, don't hold your breath for those tantalizing, single-digit subsidy mortgages, this year or next. And if you're an unemployed construction worker, pinning your hopes on a "jobs stimulus" housing bill such as this, don't wait for Congress this Christmas. Here's why:

The economic conditions that produced passage of the so-called Lugar housing assistance bill in June -- which would have subsidized 400,000 loans and created 700,000 jobs -- no longer exist. When the Lugar bill, named for sponsor Sen. Richard Lugar (R-Ind.), went to the president's desk, mortgage rates were stuck between 16 and 17 percent. Today they're nearly four percentage points lower. The 12 1/2 percent Federal Housing Administration (FHA) and Veterans Administration (VA) rate is triggering a boom in mortgage applications and sales -- without any congressional subsidies.

The strong political and industry coalition behind the earlier stimulus bill -- which came close to overriding Reagan's veto -- has weakened considerably.

Home builders, for example, who would be among the prime beneficiaries of any assistance to buyers, haven't asked Congress for any new help.

Lobbyists for the National Association of Home Builders virtually wrote the Lugar bill word-for-word early in the spring. In contrast,, the majority of the building association's members would probably oppose creation of a subsidy program during the lame-duck session, according to the association's leaders.

Michael Sumichrast, chief economist for the association, says his surveys of home builders this fall reveal a definite swing to a "free market" approach and away from federal subsidies of any kind.

Peter D. Herder, the association's first vice president for 1983 and a major Tucson home builder, puts it this way: "We don't want handouts from the government anymore to do what we should be able to achieve by simply using the proper tools in the private marketplace. We want to put private initiative back to work, not expand the federal deficit."

Herder, who supported the Lugar approach in the spring, thinks that in the wake of the Reagan veto "we've learned more than ever as an industry how to be self-reliant and how to be innovative about financing."

He cites the $50 million bond issue that he and other Arizona builders are floating this month as a prime example. The taxable-bond concept allows builders to band together and tap the capital markets on their own, often at lower rates and better terms than they'd obtain from local banks. The bonds cost the federal tax system nothing, yet allow builders greater flexibility in structuring loans for buyers.

"This is do-it-yourself financing at a large and fairly sophisticated level," says Herder. Six months ago he wasn't using such a tool. Today, he and dozens of other builders are planning to use it regularly.

Economist Sumichrast, who says he'd "personally" support a low-cost program of subsidies for first-time buyers, sees mortgage rates heading one to two percentage points lower next year than they are now.

With FHA-VA rates heading for 11 percent or less,, "It's going to be very hard to get builders behind any federal subsidy program," Sumichrast concedes.

And what chance does a home builder bailout program have in Congress if the builders themselves don't want to be bailed out? About the same chance as the proverbial snowball in you-know-where.