The Sturmpanzer IV was a development of the Panzer IV tank designed to provide direct infantry fire support, especially in urban areas. The result was the Sturmpanzer IV, which used a Panzer IV chassis with the upper hull and turret replaced by a new casemate-style armored superstructure housing a new gun, the 15 centimetres (5.9 in) Sturmhaubitze (StuH) 43 L/12 developed by Skoda. It fired the same shells as the 15 cm sIG 33 heavy infantry gun. Thirty-eight rounds, with separate propellant cartridges, could be carried. It used the Sfl.Zf. 1a sight. A MG 34 machine gun was carried that could be fastened to the open gunner's hatch, much like the arrangement on the Sturmgeschütz III Ausf. G. Early vehicles carried a MP 40 sub-machine gun inside, which could be fired through firing ports in the side of the superstructure.
| Sturmpanzer IV | |
|---|---|
| Type | Heavy assault gun |
| Place of origin |  Nazi Germany |
| Production history | |
| Designer | Alkett |
| Designed | 1942—1943 |
| Manufacturer | Alkett |
| Produced | 1943—1945 |
| Number built | 306 |
| Specifications | |
| Weight | 28.2 tonnes (62,170 lbs) |
| Length | 5.93 metres (19 ft 5 in) |
| Width | 2.88 metres (9 ft 5 in) |
| Height | 2.52 metres (8 ft 3 in) |
| Crew | 5 (driver, commander, gunner, 2 loaders) |
| | |
| Armor | Front: 100 mm (3.93 in) |
| Main armament | 15 cm StuH 43 L/12 |
| Secondary armament | 1 or 2 x 7.92 mm (0.312 in) MG 34 |
| Engine | liquid-cooled V-12 Maybach HL120TRM 300 PS (296 hp, 220 kW) |
| Power/weight | 10.64 PS/tonne |
| Suspension | two-wheel leaf-spring bogies |
| Operational range | Road: 210 km (130 mi) |
| Speed | Road: 40 km/h (25 mph) Off-road: 24 km/h (15 mph) |
The driver's station projected forward from the casemate's sloped frontal armor plate and used the Tiger I's Fahrersehklappe 80 driver's sight. The fighting compartment was (badly) ventilated by natural convection, exiting out the rear of the superstructure through two armored covers. Sideskirts were fitted on all vehicles.
Early vehicles were too heavy for the chassis, which lead to frequent breakdowns of the suspension and transmission. Efforts were made to ameliorate this from the second series onwards, with some success.
In October 1943 it was decided that the StuH 43 gun needed to be redesigned to reduce its weight. A new version, some 800 kilograms (1,800 lb) lighter than the StuH 43, was built as the StuH 43/1. Some of the weight was saved by reducing the armor on the gun mount itself. This gun was used from the third production series onwards.
Zimmerit coating was applied to all vehicles until September 1944.
