President's Reagan's plan to order several years' worth of weapons under one congressional authorization is in trouble in the Senate, with the Air Force's B1 bomber the leading case in point.

The Senate Armed Services subcommittee on strategic and theater nuclear forces not only rejected the administration's multi-year procurement plan for the B1 but also voted in closed session to reduce the production rate of the bomber.

Defense Secretary Caspar W. Weinberger is expected to contest this challenge to multi-year procurement, the centerpiece of the administration's plan to cut costs through volume production.

The Armed Services subcommittees are under pressure to limit after-inflation growth in the fiscal 1984 defense budget to 5 percent, half of what Reagan sought. And there is the political argument that the B1 is past its time and that the Air Force should concentrate its money on the "stealth" bomber instead.

Under the Senate subcommittee's recommendation, the Air Force would be limited to producing 36 B1s in fiscal 1985 and 1986 rather than jumping up to 48 in fiscal 1986. Some advocates of this limit said it was unrealistic to try to increase B1 production that sharply.

Others said the program was structured to keep it going until 200 bombers had been produced, rather than the advertised 100, and they argued that stretching out production would slow this drive.