Six manufacturers were solicited for prototype designs : Gustloff-Werke , Mauser , Johannes Großfuß Metall - und Lackierwarenfabrik , C.G. Hänel , Rheinmetall-Borsig and Heinrich Krieghoff Waffenfabrik .
Six companies were asked to design prototypes . These were : Gustloff-Werke , Mauser , Johannes Großfuß Metall - und Lackierwarenfabrik , C.G. Hänel , Rheinmetall-Borsig and Heinrich Krieghoff Waffenfabrik .