30.5 cm L/16 auf Sfl. Bär

German Reich (1943)
Assault Mortar – None Built

After the Battle of Stalingrad ended in February 1943, a great effort was made by Germany to develop heavily armored vehicles armed to be more effective at assaulting fortified positions and buildings, particularly in urban environments. The realization that such a vehicle was required came soon after fighting in Stalingrad began, and the straightforward solution to this problem was presented at Hitler’s conference on the 20th of September 1942.

“Fighting in Stalingrad has clearly resulted in the necessity of having a heavy gun in a heavily armored vehicle to fire high explosive shells capable of destroying entire houses with only a few rounds…“

The initial result of this calling was the SturmInfanterieGeschütz 33B (Eng: Assault Infantry Gun 33B), a variant of the StuG III assault gun with a heavily modified box-like casemate armed with a 15cm (5.9 in) sIG/33/1 howitzer. With 80 mm (3.15 in) of frontal armor, the StuIG 33B was capable of directly attacking fortified positions while still being adequately protected against return fire.

Twenty-four of these vehicles were completed by October 1942, with 12 of them being put into service by the end of the month and the other 12 in November. Despite being optimized for demolition work, however, it would be far from the most powerful assault vehicle designs to come out of Germany during WWII.

As though the StuIG 33B was totally inadequate for its role as a demolition vehicle, 1943 would see the manufacturing firm Krupp propose a quintessential German wonder weapon. At a total combat weight of 120 tonnes (264,555 lbs.), the 30.5 cm L/16 auf Sfl. Bär was nothing short of a behemoth. As a Sturmmörser (assault mortar) intended to reduce enemy defensive positions to rubble anywhere from several kilometers away to direct fire at point-blank range, the Bär (appropriately translated to ‘Bear’ in English) was to be matched in firepower only by towed siege artillery, railways guns, and the famous and slightly heavier Karl-Gerät siege mortar, all while having comparable armor protection to the Tiger II.

Krupp Takes The Initiative

Historian and author Michael Frölich states that the proposal for 30.5 cm L/16 auf Sfl. Bär was done on Krupp’s own initiative without any requirements being issued to firms for such a vehicle. This is a good example of Germany’s procurement system gradually breaking down as the war dragged on, as firms started to more frequently propose their own vehicle designs with homegrown requirements in the quest for more government contracts.

Sources differ on when the 30.5 cm L/16 auf Sfl. Bär was proposed. Historian and author Thomas Jentz states that Krupp proposed the concept on the 4th of May 1943, and had completed a drawing of the vehicle on the 10th. However, Frölich states that the design was presented by Dr. Erich Müller, who was head of artillery development at Krupp, to WaPrüf 4/II (Bureau for testing artillery for fortifications and fighting vehicles, of Artillery Section of Army Ordnance Office) on the 11th of March 1943 under the designation SKA 758, and given the appropriate name Bär.

Loaded For Bear

Bär was to be armed with a 30.5 cm (12 in) L/16 siege mortar in a casemate located at the rear of the vehicle. The mortar itself weighed 8 tonnes and was mounted on a carriage weighing a further 6 tonnes which was bolted onto the floor of the fighting compartment. Around the gun was a large curved mantlet weighing 2.5 tonnes. The mortar could be elevated up to 70 degrees but could not be depressed further than 0 degrees. When horizontal at 0 degrees, the gun rested on a travel lock which featured a hinged cap that swung up to cover the muzzle of the mortar and lock it in place.

The mortar could only traverse 2 degrees left or right, so when aiming, the entire vehicle would need to be turned to effectively get the mortar onto target. This issue was also faced by the French Char B1 heavy tank, which featured a hull-mounted 75 mm (2.95 in) gun that was fixed in traverse, so horizontal aiming was done purely by steering the tank. This issue was largely overcome with the development of a very sophisticated steering system which allowed very precise control of the tank during steering. Since the Bär used a transmission not designed for that sort of precision, it is possible that accurate aiming at close range would have been difficult to achieve.

However, it can be easily argued that, at close range with a 30.5 cm shell, aiming doesn’t need to be that precise.

At high elevation when firing at long range, accommodation had to be made for the massive breech of the mortar, which during recoil would travel 1 m (3.3 ft) rearward through a hole in the hull floor.

The mortar had a choice of two kinds of shell, a high explosive shell weighing 350 kg (772 lb), and an anti-concrete shell weighing 380 kg (838 lbs.). The high explosive shell had a propellant charge of 50 kg (110 lbs.) and was estimated to achieve a muzzle velocity of 355 m/s (1,165 fps) with a maximum range of 10.5 km (6.5 m). The anti-concrete shell had a 35 kg (77 lbs.) propellant charge and was estimated to achieve 345 m/s (1,132 fps) with a maximum range of 10 km (6.2 m).

Only 10 rounds were to be carried in the vehicle. However, this is not an unreasonably low number. As the shells each weighed hundreds of kilograms and a large winch mounted to the ceiling of the casemate was required to move and load them, the two loaders in the vehicle would have taken an exceptionally long time to load each shell, meaning the vehicle would not run out of ammo in any short amount of time. It also would not be unreasonable to expect very few targets to require more than one or two hits before they were no longer a threat.

According to historian and author Fritz Hahn, the 30.5 cm mortar was to be built by Škoda and would use ammunition that had already been manufactured as part of an old contract with Yugoslavia. No details about this contract are known, however.

Running Gear

To take advantage of parts commonality, the 30.5 cm L/16 auf Sfl. Bär was to be built on a chassis that made use of components from both the Panther II and Tiger II. It would be powered by the Maybach HL 230 found in the Panther, Tiger I, and Tiger II, providing 700 hp at 3000 rpm. It would also use the L 801 double differential steering system of the Tiger II, which was an upgraded version of the L 600 found in the Tiger I, and the ZF AK 7-200 7-speed gearbox of the Panther. This would have given the Bär an estimated top speed of only 20 km/h (12.4 mph).

The reason for choosing the Panther’s gearbox for the Bär is that, on 17th of February 1943, a proposal had been made recommending that Tiger II and Panther II should share a number of standardized components, including the engine (HL 230 P30), gearbox (ZF AK 7-200) and cooling system. During the time when Bär was being developed, this proposal was still in place, so considering Krupp’s involvement in the development of Tiger II, it is to be expected that they would have been well aware of the advantages of including these standardized components in the Bär. Like both Tigers and the Panther, the transmission of Bär was located at the front of the vehicle, and because the casemate and gun were located at the rear of the vehicle, the engine and cooling system were located in the center of the vehicle in front of the casemate in a layout similar to the Ferdinand tank destroyer.

As a very wide vehicle, the Bär’s tracks followed the same design process as those of Tiger I and Tiger II, in that a set of narrow transport tracks would be fitted to allow the vehicle to be transported by rail or trailer, and a set of full-width combat tracks would be fitted while the vehicle was traveling under its own power. The transport tracks were to be 500 mm (19.7 in) wide, and the combat tracks would double that at 1,000 mm (39.4 in) wide. In comparison, the Tiger II’s tracks were 660 mm (26 in) and 800 mm (31.5 in) respectively. With the transport tracks fitted, the vehicle had a width of 3.27 m (10.72 ft) and with the combat tracks this was increased to 4.1 m (13.45 ft). Despite the use of such wide tracks, at 120 tonnes, the Bär would have had very poor performance off-road, with a ground pressure estimated to be around 1.13 kg/cm2 (16.07 psi), compared to the Tiger II’s 0.76 kg/cm2 (10.8 psi).

The Bär featured overlapping 800 mm (31.5 in) road wheels but it is not confirmed if it was to use the same sprocket and wheels as on Tiger II. However, as the vehicle was intended to standardize on components with Tiger II, it is reasonable to expect that it would. Hilary Doyle, in his illustration of the Bär, presents it as having the sprocket, idler and steel-rimmed road wheels of Tiger II. This is supported by Thomas Jentz describing the road wheels as “rubber cushioned”, likely referring to the ring of rubber sandwiched under the wheel hub on either side of the wheel as a way to reduce wear without using rubber tires like those used on earlier Tiger I road wheels, which were prone to wear and contributed to rubber wastage.

While both Tigers and the Panther used torsion bar suspension which took up most of the space on their hull floors, Bär was instead, to use leaf springs. It is not known what these suspension units would have looked like but one of the main reasons for choosing leaf springs instead of torsion bars was to facilitate the inclusion of a baseplate built into the rear of the hull floor. This design feature would not be possible if the Bär used transverse torsion bars under a false floor like the Tiger and Panther. Prior to firing, possibly only for high elevation during low threat engagements, this base plate would be lowered onto the ground and locked in place. The purpose of this was to help absorb the massive amount of recoil generated by the gun during firing, which was estimated to reach around 160 tonnes of force. This design concept is present in some produced vehicles, such as the M55 and M110 Self-Propelled Howitzers, both of which feature a large dozer-like plate at the rear of the vehicles – known as a ‘recoil spade ‘ – which lower down onto the ground for the same purpose of absorbing recoil that could otherwise damage the vehicle, particularly the suspension.

Layout

The hull of Bär greatly resembled that of the Tiger II in both shape and protection. The reason for such a level of protection was that, as an assault mortar, the Bär had to be capable of resisting incoming fire from some of the most powerful AT weapons of the time. The floor armor was also intended to protect against mines, a sensible concern for an assault vehicle. To achieve this, it had the following armor values:

• Upper Hull Front: 130 mm (5.12 in) at 55 degrees from vertical, 222 mm (8.74 in) LoS (Line of Sight) thickness.
• Lower Hull Front: 100 mm (3.94 in) at 55 degrees from vertical, 173 mm (6.81 in) LoS thickness.
• Upper Sides: 80 mm (3.15 in) flat transitioning into 80 mm at 25 degrees from vertical, 88 mm (3.46 in) LoS thickness.
• Lower Sides: 80 mm flat.
• Rear Hull : 80 mm at 30 degrees from vertical, 93 mm (3.66 in) LoS thickness.
• Roof: 50 mm (1.96 in).
• Front Floor: 60 mm (2.36 in).
• Rear Floor: 30 mm (1.18 in).
• Mantlet: 80-130 mm (3.15-5.12 in), 130-300 mm (5.12-11.8 in) LoS thickness.
• Casemate Front: 130 mm, 130-170 mm (5.120-6.69 in) LoS thickness.

The driver was positioned in the front left of the vehicle and the radio operator was on the right. Each had a swing-out hatch like those found on the Panther and Tiger II and a single rotatable periscope. Despite the intended use of the vehicle, the radio operator did not have a ball-mounted machine gun for close protection against infantry. In fact, no other weapon is described as being present on the vehicle, although it can be reasonably assumed the crew’s personal weapons would be carried. Because of the placement of the engine, these two crewmen were physically separated from the rest of the crew who were in the rear fighting compartment. The commander and gunner were positioned on either side of the mortar and each had their own swing-out style cupola with 8 periscopes. It is notable that, because of the vehicle’s 3.55 m (11 ft) height, the cupola periscopes were angled downwards to reduce the massive blindspot that would otherwise be present all around the vehicle. The two loaders were positioned at the rear of the casemate, where they could operate the winch and load the mortar, and there was a hatch in the lower rear hull for them to enter or leave the vehicle.

It should also be noted that, in the drawing showing the interior layout of the Bär, what appears to be the elevation wheel for the mortar can be seen significantly below the positions of the gunner and commander on the gun carriage. This suggests two possible options. One option was that the gunner did not fight with his head up in his cupola, but he instead moved down next to the gun carriage and adjusted the mortar without actually seeing what he was aiming at himself, with the commander directing him using his own sight. A second possibility was that one or both or the loaders had a second duty in adjusting the mortar and it was the gunner who directed them using his own sight (no actual gunsight is shown in the drawings). With the placement of the elevation wheel, it was not possible to be up in the cupola while adjusting the mortar.

One other mysterious feature of the Bär shown in the drawing is the object protruding from the rear of the casemate. As it is shown with a shell inside it, it can be assumed to have been some kind of loading tray for loading shells into the vehicle and then stowed in their ready racks. What is not clear however is how it functioned. The rear of the object appears to be a wall the same thickness as the armor on the rear of the casemate, suggesting the object slid inwards into the vehicle much like a drawer, so that the rear was flush with the armor. If that was the case, it is not known if this drawer action was done specifically to move the shells into the vehicle where they were then moved by the internal winch, or if the tray stayed in place during loading and the shells were manually pushed in from the outside or were pulled in by some kind of mechanical rammer.

The loading process would have been time-consuming and undoubtedly would require the assistance of a Munitionsschlepper (ammunition tractor) with its own external crane, much like the Munitionsschleppers that accompanied the Karl-Gerät siege mortars. This is supported by Fritz Hahn who states the Bär would indeed be supported by specialist ammunition-carrying vehicles, however, no other descriptions of this vehicle are provided.

Hahn also states that a lighter version of the Bär had been designed, weighing significantly less at 95 tonnes. However, once again, no other details are provided. This is likely because Hahn wrote about the vehicle four decades after WWII ended while relying mostly on his recollections, and with his personal experience not being related to armored vehicles, without evidence, it is highly likely that this claim is not accurate.

Misconceptions

As a unique and imposing vehicle, the Bär has proved popular amongst scale modelers, with modeling companies such as Amusing Hobby and Trumpeter producing their own model kits of the vehicle. However, a number of inexplicable inaccuracies are present in the models of both the aforementioned modeling companies.

These include:

• The presence of a hull-mounted ball machine gun. While heavily inspired by the Tiger II, there is no evidence that the Bär possessed a hull machine gun.
• A single cupola. While it is a sensible change to an impractical design, the Bär did not feature one cupola on the casemate roof, but a pair. As well as this, the cupolas on these models are not correctly designed in that the periscopes are not angled downwards to increase visibility, unlike the periscopes of the original design.
• Fully sloped upper side armor. According to Doyle’s drawings for the Bär, the lower half of the sponson’s side armor was to be vertical, with the rest of the upper side armor all the way to the casemate roof being sloped at 25 degrees. There is no primary evidence that the Bär’s sponsons were fully sloped like that of Panther or Tiger II.
• A complex cast casemate face. One of the most glaring changes to the Bär’s design in models is the presence of a large complex cast piece as the casemate’s frontal armor. There is no evidence to support such a design. While the Bär’s actual casemate face is highly curved in the vertical plane, it is completely straight in the horizontal plane. A comparable existing design would be that of the Maus, whose turret face very much resembles the shape of the Bar’s casemate face. This was produced by bending a straight armor plate using a huge metal press.

Fate and Conclusion

On the 27th of May 1943, in a meeting between the manufacturing firm Alkett and the Waffenkommission, Alkett revealed plans for a competing design in the form of a self-propelled 38 cm (14.96 in) mortar. Development for the vehicle was approved and by October the first prototype, a 38 cm rocket launcher mounted in a casemate built on a Tiger I chassis, was built and presented to Hitler. This vehicle would see further development and entered production as the 38 cm RW61 auf Sturmmörser Tiger. It is more commonly known as Sturmtiger.

30.5 cm L/16 auf Sfl. Bär seemingly ceased development sometime after Alkett revealed their competing design, and it is not hard to understand why. At 120 tonnes, it was significantly underpowered and, despite its enormous tracks, it would have had poor mobility and would have been vulnerable to sinking on anything but hard ground. While it could have been technically capable of fulfilling its intended role, the Sturmtiger demonstrated that the role could be more effectively filled by a vehicle half the size and weight without requiring vast resources to function.

With the existence of a later blueprint showing a significantly altered design, it is very possible that development of the Bär actually continued even after the introduction of the Sturmtiger, until at least December 1944.

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Artists representation of the 30.5 cm L/16 auf Sfl. Bär in red-oxide primer with a 1.83 meter (6 ft) man for scale. Illustration produced by the author, Mr. C. Ryan, and funded by our Patreon Campaign.

Specifications
Dimensions (L-W-H)	8.2 x 3.27-4.1 x 3.55 meters (26.9 x 10.7-13.45 x 11.65 feet)
Total weight, battle-ready	120 tonnes (264,555 lbs.)
Crew	6 (Commander, Gunner, Driver, Radio Operator, 2 Loaders)
Propulsion	Maybach HL230 P30 700 hp 3000 rpm
Speed (road)	20 km/h (12.4 mph)
Armament	30.5 cm L/16 Mortar (10 rounds)
Armour	Hull 30-130 mm, Casemate 80-130 mm
For information about abbreviations check the Lexical Index

Sources

Thomas L. Jentz, Panzer Tracts No. 8: Sturmgeschuetz – s.Pak to Sturmmoerser
Thomas L. Jentz, Panzer Tracts No. 20-1 Paper Panzers – Panzerkampfwagen & Jagdpanzer
Michael Fröhlich, Überschwere Panzerprojekte Konzepte und Entwürfe der Wehrmacht
Fritz Hahn, Waffen und Geheimwaffen des deutschen Heeres 1933-1945
Michael Sowodny, German Armored Rarities 1935-1945

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