StuG III Ausf. F (Sd.Kfz 142/1) was the first real up-gunning of the StuG, this version uses the longer 7.5 cm StuK 40 L/43 gun. Firing armour-piercing Panzergranat-Patrone 39, StuK 40 L/43 could penetrate 91 mm of armour inclined 30 degrees from vertical at 500 m, 82 mm at 1,000 m, 72 mm at 1,500 m, 63 mm at 2,000 m, allowing Ausf. F to engage most Soviet armoured vehicles at normal combat ranges. This change marked the StuG as being more of a tank destroyer than an infantry support vehicle.
An exhaust fan was added to the rooftop to excavate fumes from spent shells, to enable the firing of continuous shots. Additional 30 mm armour plates were welded to the 50 mm frontal armour from June 1942, making the frontal armour 80 mm thick. From June 1942, Ausf. F were mounted with approximately 13 inch (334 mm to be exact) longer 7.5 cm StuK 40 L/48 gun. Firing above mentioned ammunition, longer L/48 could penetrate 96 mm, 85 mm, 74 mm, 64 mm respectively (30 degrees from vertical).
It was produced between March–September 1942. They were built 366 units.