In September of 1939, German High Command ordered Krupp to design a heavy panzerjager armed with 105 or 128mm gun that would be able to destroy enemy tanks and heavily fortified positions (such as pillboxes).
In early/mid 1941, Krupp-Gruson produced two prototypes of such a vehicle and on March 31st of 1941, first was presented to Adolf Hitler. The Fuhrer ordered further development of heavy panzerjagers armed with either 105mm or 128mm guns. He also ordered that the production of Selbstfahrlafette 10.5cm must start in the Spring of 1942, but it was later on cancelled in favour of other vehicles.
Selbstfahrlafette 10.5cm was armed with Krupp's 105mm K 18 L/52 gun with limited traverse of 8 degrees (left and right) and based on modified Panzer IV Ausf A's chassis. The gun itself was developed by Krupp and Rheinmetall from 105mm sK 18 L/52 heavy field gun and was mounted with a muzzle break.
The gun was capable of penetrating 111mm of 30 degrees sloped armor plate at 2000 meters.
It was mounted in lightly armored (armor protection ranged from 10mm to 50mm),
open at rear superstructure and for local defense machine gun (7.92mm MG34) was carried inside as well.
Vehicle was powered by Maybach HL 120 TRM engine with total power of 300 horsepower (same as Panzer IV) allowing it to travel at the speed of 40km/h.
Originally, two prototypes
were assigned to Panzerjager Abteilung 521
in preparations for upcoming attack on Gibraltar. At the beginning of Operation Barbarossa, both were assigned
to 3rd Panzer Division and were troop tested. One of them was lost when its ammunition exploded
(as reported it was then captured the Soviets) and the second one was brought back to the factory in October of 1941.
The further fate of the surviving vehicle is unknown.
Both prototypes proved to be very effective against Soviet KV-I, KV-II and T-34 tanks. Serial production did not take place, while even limited numbers would prove to be very useful to the front line troops faced with superior Soviet armor in 1941/42.
Specifications
Weight:
25000kg
Crew:
5 men
Engine:
Maybach HL 120 TRM / 12-cylinder / 300hp
Speed:
40km/h
Range:
Road: 200km
Lenght:
7.52m
Width:
2.84m
Height:
3.25m
Armament:
105mm K 18 L/52 & 7.92mm MG34 (1 x MG34 - carried inside)
Ammo:
105mm - 20-25 rounds 7.92mm - 600 rounds
Armor (mm/angle):
Front Hull: 50/12
Front Superstructure: 50/10
Front Turret: 30/14
Gun Mantlet: 50/10
Side Hull: 20/0
Side Superstructure: 20/0
Side Turret: 20/14
Rear Hull: 20/10
Rear Superstructure: 20/10
Rear Turret: 20/20
Hull Top / Bottom: 10/90
Superstructure Top / Bottom: 12/90
Turret Top: open
In early May of 1942, a new design of Sturmpanzer, the Bär (Bear) was proposed.
On March 4th of 1943, Krupp proposed development of new Sturmgeschütz armed with 305mm L/16 mortar and first drawings were ready in May.
It was to be armed with a 305mm gun mounted in the superstructure, based on the modified chassis of the then new Panzerkampfwagen VI Tiger (Tiger I) heavy tank utilized some Panther components with new suspension developed by Krupp.
The new vehicle was to weight 120 tons.
This new Sturmpanzer was to be powered by a 12-cylinder Maybach HL 230 P 30 engine producing 700hp. This would have al-lowed the vehicle to travel at a maximum speed of approximately 20km/h [12 mph]. Bär was to be armed with a rigidly-mounted 305mm KwK L/16 gun installed in an armored superstructure in the back of the hull. The main gun could only be elevated from 0 to 70 degrees and had a range of 10,500 meters [11,400 yards]. Each 305mm round weighed 350kg [770 pounds] and carried a 50kg [110 pound] charge. The interior storage space allowed for only 10 rounds.
Bär was to be 8.2 meters [26.7 feet] long, 4.1 meters [13.65 feet] wide and 3.5 meters [11.4 feet] high. Armor was sloped and protection ranged from 80mm on the sides to 130mm at the front. Sturmpanzer Bär was to be operated by a crew of six - commander, gunner, two loaders, driver and radio-operator. The project never left the drawing board, but was a step in the development of the Sturmtiger.
In late 1943, Zahnradfabrik Augsburg equipped normal (turretless) Panzerkampfwagen IV Ausf G/H
with newly developed hydraulic steering system. Thoma (non-liquid) oil drive transmission was installed
and drive sprocket was replaced with the new one.
The power train consisted of twin oil pumps driven by Maybach HL 120 TRM engine. In order
to accommodate all the changes, entire engine deck and rear was modified. In mid 1944, this
prototype was fitted with modified hydraulically operated turret. Tests were carried on
but were never concluded and for testing
purposes the only prototype was send to Russia and served with the Waffen SS unit.
At the end of the war, this vehicle was captured by the US Army and was sent to United States for further examination. Tests were never concluded and
this vehicle is still at Aberdeen U.S Army Proving Grounds in Maryland.
Panzerkampfwagen IV mit hydrostatischen Antrieb at Aberdeen. Photo provided by Alec Corapinski.
