In the early 1980s the manufacturing of the HK G3 and HK 21, under license from Heckler & Koch, by INDEP allowed for the import of German weapon manufacturing machinery and German technical know-how, which stimulated development of new firearms design in Portugal.

The Lusa shared the concept and design layout of the HK MP5 and Uzi submachine gun. As such, its trigger group is nearly identical to that of the MP5 and the barrel can be quickly changed, as in the Uzi. The bolt and carrier are one integrated unit.

The weapon never reached mass industrial production and work on it ground to a halt in 1992, at a cost of 2.5 million dollars. The MP5 soon replaced this weapon’s intended usage in the Portuguese police forces.