New Army tests show that its main battle tank is wonderful, especially in its ability to shoot while on the move -- when it works. The problem is that the tests also show M1 tank stopping for "unscheduled maintenance" -- sometimes caused by breakdowns in major components -- as often as every 30 miles.

The General Accounting Office reported its analysis of the test yesterday at a hearing at which Sen. William Proxmire (D-Wis.) added to the bad news about the the Army's readiness for tank warfare in Europe and about problems created by complex technology. Testimony indicated that expensive new M1s might be less reliable than tanks already deployed.

Proxmire disclosed that the Army has recalled from Europe 543 tanks that "turned out to be useless." He identified the tanks -- which had turret, maintenance, logistical support, and other problems, and cost about $675 million in 1981 dollars -- as the A2 version of the M60. Earlier and later versions, the A1 and the A3, are still in use.

Eventually, M1s will replace the A3s. Do the M1s break down so often that they could be inferior to the A3s under battlefield conditions? Proxmire asked Donald J. Horan, director of the GAO's Procurement, Logistics and Readiness Division. "Yes, sir," Horan replied.

Walton H. Sheley Jr., chief of the congressional watchdog agency's Mission Analysis and Systems Division, expressed hope that the M1's problems can be remedied. "If not, we've got a lemon," he told Proxmire's Joint Economic subcommittee.

Proxmire said he expects the cost of each tank to run as high as $3 million, raising the program cost to $19 billion -- a $5 billion overrun of the 1974 estimate after adjustment for increased quantities.

The Army plans to buy 7,058 M1s and estimated the cost at $2.5 million each. In 1974 the estimated unit cost was $900,000 and the Army planned to purchase 3,323.

These current figures, subcommittee counsel Richard F. Kaufman said, also include neither an $800 million "product improvement" program nor the costs of ammunition, replacement of the 105-mm gun with a 120-mm version, fuel (burned at the rate of four gallons to the mile), logistical support such as fuel trucks, and maintenance.

Republican Sens. Roger W. Jepsen (Iowa) and Steve Symms (Idaho) contended that after allowing for inflation, the price of an M1 computed in 1972 dollars has risen only slightly. Sheley said that "a good part" of the blame could be attributed to inflation, which he said is much higher in defense industries than in the overall economy.

The new operational tests of the M1 ran from September, 1980, to June, 1981, and were made with four tanks at Ft. Knox, Ky., and 41 at Ft. Hood, Tex.

The "tentative results" generally showed that "the M1 was falling short of achieving its reliability, durability, and maintenance goals," Sheley testified.

He found it "conceivable" that final analysis of the test scores will show that the "combat mission reliability" goal -- a mean of 320 miles between failures -- are being met or exceeded. But, he said, it is "virtually certain" that the goals for durability of the drive train (4,000 miles without replacement of the troublesome turbine engine, transmission or the "final drive") and for maintenance (1.25 man-hours of maintenance for each hour of operation) "will not be achieved."

Proxmire suggested it would be a "blunder" to send M1s to Europe before major bugs are ironed out and before support facilities are in adequate supply. He said the M1 is an example of "this marvelous new technology" that has created staggering reliability, maintenance and support problems.