The first prototype was designated BM.4b and was fitted with 67 kW (90 hp) Walter Vega radial engine.

The second prototype, flown on 2 April 1928, was designated BM.4d and fitted with the Polish experimental 63 kW (85 hp) WZ-7 radial engine, then refitted with 60 kW (80 hp) Le Rhône 9C rotary engine and redesignated BM.4a.

The BM.4a became a production variant, because the Polish Air Force had a store of Le Rhône 9C engines.

Three BM.4a's were converted to BM.4e of 1930 with the Polish experimental 63 kW (85 hp) Peterlot radial engine, the BM.4f of 1931 with the Polish experimental 89 kW (120 hp) Skoda G-594 Czarny Piotruś radial engine, and the BM.4g of 1931 with a 75 kW (100 hp) de Havilland Gipsy I inline engine, which competed against the RWD-8 in a search for a standard trainer aircraft, but was not selected.

Due to the Samolot factory's closure in 1930, the BM.4h was developed at the PWS (Podlaska Wytwórnia Samolotów) and built there in 1932 in a series of about 50 aircraft.

In 1936 the Polish Air Force handed over their remaining 23 BM.4h's to civilian aviation - most to regional aero clubs, some to the Ministry of Communication.