The aircraft was designed by Ryszard Bartel in the Samolot factory in Poznań. It was a development of the Bartel BM.2, which did not advance beyond the prototype stage. Thanks to a lower weight than the BM.2, it could use lower-powered engines, so its performance was actually improved. Its performance was also superior to the Hanriot H.28, used by the Poles and licence-built by Samolot. The BM.4 prototype was flown on 20 December 1927 in Poznań. It had good handling and stability and was resistant to spinning. A distinguishing feature of all Bartels was an upper wing of a shorter span, because lower and upper wing halves were interchangeable (i.e. the lower wingspan included the width of the fuselage).