Senate opponents of building any more than four B-1 bombers adopted a legislative straegy yesterday designed to shoot down the effort of the House Appropriations Committee to keep the airplane program flying.

In a frontal assault on President Carter's defense program, the House Appropriations Committee voted 34 to 21 on Wednesday to force the Air Force to build six rather than four B-1 prototypes.

Carter told Congress that four B-1 bombers would be enough for research and asked Congress to let him change the fiscal 1977 budget accordinly, saving $426 million. If either the House of the Senate fails to give its approval by Oct. 4, Carter is required to release the B-1 money appropriated earlier.

Specifically, the 1974 budget control act requires the President to make "available for obligation" the money he sought to save if Congress does not approve his budget changes within 45 days of their submission. The changes are rescissions.

Although the 45 days for approving the B-1 changes is up on Oct. 4, Chairman George H. Mahon (D-Tex.) of the House Appropriations Committee said yesterday that Pentagon executives probably can find a way to make the money technically available without actually obligating it or spending it.

House leaders decided yesterday that the budget control act would not allow Carter to make another rescission request regarding the B-1. "It's out of my hands," Mahon said in an interview yesterday.

Senate strategists decided to use the fiscal 1978 supplemental defense appropriation bill as the vehicle to end-run the House Appropriations Committee. The full House is scheduled to vote on that measure this Tuesday.

After the House passes it, the plan is for the Senate Appropriation Committee to add language to the measure "de-appropriating" the fiscal 1977 money that would pay for the fifth and sixth B-1 bombers which Carter considers a waste of money. Either Sen John C. Stennis (D-Miss.) or Sen. William Proxmire (D-Wis.) on the Senate Appropriations Committee is expected to sponsor the amendment during the markup of the bill late next

The Senate has been more supportive of Carter's efforts to change the B-1 program, voting to cut out money for production by comfortable margins in both the Senate Appropriations Committee and on the floor. If the Senate passes the supplemental bill with the rider denying B-1 money for the fifth and sixth prototypes, the House and Senate will hold a conference to work out difference in the two bills.

The resulting compromise version of the supplemental money bill will be voted on by the full membership of the House and Senate, meaning the B-1 rider could not be blocked by the House Appropriations Committee. Thus, if this legislative strategy works, the full House will have a chance to decide the immediate future of the B-1 bomber.

Another rider is expected to be attached to the same bill to enable Carter to save $105 million earmarked for building 50 additional Minuteman III missiles which the Pentagon has said it does not need.