From the 120th model F onwards the longer 7.5 cm StuK 40 L/48 was fitted and this was retained until StuG III production ceased in the spring of 1945. Vehicles thus armed were officially designated "7.5 cm Sturmgeschütz 40, Ausf G (Sd Kfz 142/1)". The combat weight of the StuG III had now been raised to 23.9 tons and the price per vehicle was RM 82,500. From 1943 onwards, in common with the basic Pz Kw III series, armoured side aprons were fitted and the MG 34 or 42 was installed for local defence. Total StuG production was: 3041 in 1943; 4850 in 1944 and 123 in 1945.
The final variants of the StuG 40 had partially cast superstructures and cast Topfblende (pot mantlet) ["Saukopf" (pig's head)] mantlets. From the end of 1943 and the beginning of 1944 the armour was improved, without increasing the thickness, by interlocking the bow plates, and by this means a greater degree of resistance was achieved. It was planned to tum out 220 assault guns per month by June 1943. Of these 24 were to have been equipped with a light howitzer. These vehicles which had already been produced during 1942 with the description "10.5 cm Feldhaubitze 42" (Sd Kfz 142/2), were similar in construction to the StuG 40 and had the 10.5 cm Sturmhaubitze (assault howitzer) 42 L/28 as their main armament. Thirty-six rounds of 10.5 cm ammunition were carried. This weapon had originally been fitted with a muzzle brake (as a field piece) so that the gun could fire supercharge. Army Instruction Leaflet 1944 No 635 however ordered the removal of the muzzle brake on future production. Where the brake was fitted to the 10.5 cm StuH 42 this was retained until it became unserviceable. If no other StuH 42 brake was available for replacement, then a brake from the leFH 18 M or the leFH 18/40 was sometimes fitted as a substitute. The gun could then no longer fire supercharge. Some vehicles of the assault gun series were not fitted with guns but were used as ammunition carriers, designated "Munitionspanzer III".