This was one of a series of experimental rounds started in 1931 for the Karabinek KP-32 anti-tank rifle designed by Józef Maroszek as his academic thesis at the Faculty of Engineering at the Warsaw University of Technology. Trials were done around 1934-35 by the Commission for Trials on behalf of the Infantry School (Komisja Doswladczalna, C.W.D.) in Rembertow, just outside Warsaw with prototypes constructed by the Państwowa Fabryka Karabinów works in Warsaw. This was the forerunner of the wz 35 KB“UR” anti-tank rifle, commonly known as the 7,92 x107 Marozcek.