 It was available in two versions, the original (sometimes referred to as Haubits 77 A) with a 38 calibre barrel and sliding block mechanism, and the later FH77 B export version with a 39 calibre barrel and an interrupted screw breech.In the 1960s, Sweden started to look for a replacement for the French Haubits F (Obusier de 155 mm Modèle 50).The American M109 howitzer was offered and tested.