No, Hembrug did a large part but not everything. For example, most large caliber navy/coastal cases (5 cm up to 24 cm) up to about 1920 are made by Patronenfabrik Karlsruhe. Later Hembrug started producing these up to 15 cm, never seen a Hembrug made 24 cm so I think they where limited in size. But "we" also imported a lot of cases interwar, for example from ENZ (4,7 cm Bohler), Raufoss (3,7 cm M38 AT and 8,8 cm submarine deck gun, some KNIL mountian guns), Rheinmetall (20x105B and 20x138B). Probably more, as I am doing this from my head.