Common features of the two weapons included a wooden butt and forward pistol grip; the most noticeable difference was the magazine extending downwards in the Mors rather than to the left side of the ERMA.

The SMG was to be issued to some of the infantry units, as well as to tank crews and boarding parties of the Polish Navy and armoured trains.

The first trial series of 36 was ordered in March 1939 and additional purchases were planned.

However, until September 1939 the Fabryka Karabinów in Warsaw produced only 39, 3 of these being the prototypes (however some sources state that up to 52 were manufactured).

[2] After the start of hostilities, all were issued to the 3rd Rifle Battalion, which used them during the battle for Warsaw, and to the staff company of the 39th Infantry Division.