Stug III Variants
- StuG III prototypes (1937, 5 produced on Panzer III Ausf. B chassis): by December 1937, two vehicles were in service with Panzer Regiment 1 in Erfurt. Vehicles had eight road wheels per side with 360-millimetre (14 in) wide tracks, 14.5 mm thick soft steel superstructure and the 7.5 cm StuK 37 L/24gun. Although not suitable for combat, they were used for training purposes as late as 1941.
- StuG III Ausf. A (Sd.Kfz. 142; January–May 1940, 30+6 produced by Daimler-Benz): first used in the Battle of France, the StuG III Ausf. A used a modified 5./ZW chassis (Panzer III Ausf. F) with front armour strengthened to 50 mm. The last six vehicles were built on chassis diverted from Panzer III Ausf. G production.
- StuG III Ausf. B: (Sd.Kfz 142; June 1940–May 1941, 300 produced by Alkett) Modified 7./ZW chassis (Panzer III Ausf. H), widened tracks (380 mm). Two Rubber tires on each roadwheel were accordingly widened from 520 × 79 mm to 520 × 95 mm each. Both types of roadwheel were interchangeable. The troublesome 10-speed transmission was changed to a 6-speed one. The forwardmost return rollers were re-positioned further forward, reducing the vertical movements of the tracks before they were fed to the forward drive sprocket, and so reduced the chance of tracks being thrown. In the middle of production of the Ausf. B model, the original drive sprocket with eight round holes was changed to a new cast drive sprocket with six pie slice-shaped slots. This new drive wheel could take either 380 mm tracks or 400 mm wide tracks. 380 mm tracks were not exclusive to new drive wheels. Vehicle number 90111 shows the older drive wheel with wider 380 mm tracks.
- StuG III Ausf. C: (Sd.Kfz 142; April 1941, 50 produced) Gunner's forward view port above driver's visor was a shot trap and thus eliminated; instead, superstructure top was given an opening for gunner's periscope. Idler wheel was redesigned.
- StuG III Ausf. D: (Sd.Kfz 142; May–September 1941, 150 produced) Simply a contract extension on Ausf. C. On-board intercom installed, otherwise identical to Ausf. C.
- StuG III Ausf. E: (Sd.Kfz 142; September 1941 – February 1942, 284 produced) Superstructure sides added extended rectangular armoured boxes for radio equipment. Increased space allowed room for six additional rounds of ammunition for the main gun (giving a maximum of 50) plus a machine gun. One MG 34 and seven drum-type magazines were carried in the right rear side of the fighting compartment to protect the vehicle from enemy infantry. Vehicle commanders were officially provided with SF14Z stereoscopic scissor periscopes. Stereoscopic scissor type periscopes for artillery spotters may have been used by vehicle commanders from the start.
- StuG III Ausf. F: (Sd.Kfz 142/1; March–September 1942, 366 produced) 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, the 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 the 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 evacuate 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).
- StuG III Ausf. F/8: (Sd.Kfz 142/1; September–December 1942, 250 produced) Introduction of an improved hull design similar to that used for the Panzer III Ausf. J / L with increased rear armour. This was 8th version of the Panzer III hull, thus the designation "F/8". This hull has towing hook holes extending from side walls. From October 1942, 30 mm thick plates of additional armour were bolted on to speed up the production line. From F/8, the 7.5 cm StuK 40 L/48 gun was standard until the very last of the Ausf. G. Due to the lack of double baffle muzzle brakes, a few L/48 guns mounted on F/8s were fitted with the single baffle ball type muzzle brake used on the Panzer IV Ausf. F2/G.
- StuG III Ausf. G (Sd.Kfz. 142/1; December 1942 – April 1945, ~8,423 produced, 142 built on Panzer III Ausf. M chassis, 173 converted from Panzer III): The final and by far the most common of the StuG series. Upper superstructure was widened: welded boxes on either sides were abandoned. This new superstructure design increased its height to 2160 mm. The back wall of the fighting compartment got straightened, and the ventilation fan on top of the superstructure was relocated to the back of the fighting compartment. From March 1943, the driver's periscope was abandoned. In February 1943, Alkett was joined by MIAG as a second manufacturer. From May 1943, side hull spaced armour plates (Schürzen) were fitted to G models; these were primarily intended for protection against Russian anti-tank rifles, but were also useful against hollow-charge ammunition. Side plates were retro-fitted to some Ausf. F/8 models, as they were to be fitted to all front line StuGs and other tanks by June 1943 in preparation for the battle of Kursk. Mountings for the Schürzen proved to be inadequate, as many were lost in the field. From March 1944, an improved mounting was introduced; as a result, side skirts are seen more often with late model Ausf G. From May 1943, 80 mm thick plates were used for frontal armour instead of two plates of 50 mm + 30 mm. However, a backlog of StuGs with completed 50 mm armour existed. For those, a 30 mm additional armour plate still had to be welded or bolted on until October 1943.
From December 1942, a square machine gun shield for the loader was installed, allowing an MG34 to be factory installed on a StuG for the first time. F/8 models had machine gun shields retro-fitted from early 1943. The loader's machine gun shield was later replaced by rotating machine gun mount that could be operated by the loader inside the vehicle sighting through a periscope. In April 1944, 27 of them were being field tested on the Eastern front. Favourable reports led to installation of these "remote" machine gun mounts from the summer of 1944.
From November 1943, G versions were fitted with the Topfblende pot mantlet (often called Saukopf "Pig's head") gun mantlet without a coaxial mount. This cast mantlet, which had a sloped and rounded shape, was more effective at deflecting shots than the original boxy mantlet that had armour varying in thickness from 45 mm to 50 mm. The lack of large castings meant that the trapezoid-shape mantlet was also produced until the very end. A coaxial machine gun was first added to boxy mantlets, from June 1944, and then to cast Topfblende, from October 1944, in the middle of "Topfblende" mantlet production. With the addition of this coaxial machine gun, all StuGs carried two MG 34 machine guns from fall of 1944. Some previously completed StuGs with a boxy mantlet had a coaxial machine gun hole drilled to retrofit a coaxial machine gun; however, Topfblende produced from November 1943 to October 1944 without a machine gun opening could not be tampered with. Also from November 1943 onwards, all-metal return rollers of a few different types were used due to lack of rubber supply. Zimmerit anti-magnetic coating to protect vehicles from magnetic mines was applied only from September 1943 to September 1944.
In 1942, a variant of the StuG Ausf. F was designed with a 105 mm (4.1 in) true howitzer instead of the 7.5 cm StuK 40 L/43 cannon. These new vehicles, designated StuH 42 (Sturmhaubitze 42, Sd.Kfz 142/2), were designed to provide infantry support with the increased number of StuG III Ausf. F/8 and Ausf. Gs being used in the anti-tank role. The StuH 42 mounted a variant of the 10.5 cm leFH 18 howitzer, modified to be electrically fired and fitted with a muzzle brake. Production models were built on StuG III Ausf. G chassis. The muzzle brake was often omitted due to the scarcity of resources later in the war. Alkett produced 1,299 StuH 42 from March 1943 to 1945, the initial 12 vehicles were built on repaired StuG III Ausf. F and F/8 from the autumn of 1942 to January 1943.
StuG III (Flamm)
In 1943, 10 StuG IIIs were converted to the StuG III (Flamm) configuration by replacing the main gun with a Schwade flamethrower. These chassis were all refurbished at the depot level and were a variety of pre-Ausf. F models. There are no reports to indicate that any of these were used in combat and all were returned to Ausf. G standard at depot level by 1944.
In late 1941, the StuG chassis was selected to carry the 15 cm sIG 33 heavy infantry gun. These vehicles were known as Sturm-Infanteriegeschütz 33B. Twenty-four were rebuilt on older StuG III chassis of which twelve vehicles saw combat in the Battle of Stalingrad, where they were destroyed or captured. The remaining 12 vehicles were assigned to 23rd Panzer Division.
Due to the dwindling supply of rubber, rubber-saving road wheels were tested during 8–14 November 1942, but did not see production.
StuG III G Panzer Brigade 150
Modifications to disguise the Stug for operations in the Ardennes
Bombing raids on the Alkett factory resulted in significant drops in StuG III production in November 1943. To make up for this loss of production, Krupp displayed a substitution StuG on a Panzer IV chassis to Hitler on 16–17 December 1943. From January 1944 onwards, the StuG IV, based on the Panzer IV chassis and with a slightly modified StuG III superstructure, entered production.
Cement Armoured Stug IIIs
Field modifications were made to increase the vehicle's survivability, resulting in diversity to already numerous variants; cement plastered on front superstructure, older Ausf.C/D retrofitted with a KwK 40 L/48 gun, Ausf.G mounting Panzer IV cupola, a coaxial MG34 through a hole drilled on a boxy mantlet, et cetera.
The Soviet SU-76i self-propelled gun was based on captured StuG III and Panzer III vehicles. In total, Factory #37 in Sverdlovskmanufactured 181 SU-76i plus 20 commander SU-76i for Red Army service by adding an enclosed superstructure and the 76.2 mm S-1 tank gun.