The time had come to modernize the BM 230 Victor. The BM 320 D Buster was the next stage in the development. It had a three-cylinder Perkins turbulence chamber engine, a Terra-Trol hydraulic system, and a five-speed gearbox with independent power take-off. A two-stage clutch is available as an alternative to a clutch-dependent power take-off. The demand for a small diesel tractor was high in the Nordic Countries, but not so high in other markets, where a Bolinder diesel engine in the tractor would have been preferred. But more of the Buster were made yearly than any other BM tractor. In the 1963, the record year, no less than 5 336 Busters were made. After a time, the Buster also became available with a Volvo gasoline engine as an alternative to the Perkins diesel, but this was not a success. The end of the era of carburettor tractors was past. Even so, 650 units of the BM 320 B were made in 1962–63.
Although the period of manufacture was short, many improvements were introduced. A proper instrument panel with tractormeter was introduced, the design of the pedals was improved, more effective protection for the brakes was fitted, better seat suspension was added, and so on. But the most significant improvement was the two-speed power take-off. The two-speed power take-off was primarily intended to compensate for shortcomings in the gearbox and gear ratios, but it became something of a sales success. The number of speeds available for machines powered from the power take-off was doubled. This made it possible to exploit the higher available power output for threshing machines, or alternatively to have a lower engine speed, quieter running and better fuel economy with machines with a low power requirement. The Buster had successors in the form of the T 400 and T 430.