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15cm sIG33(Sf) auf Panzerkampfwagen I Ausf B

15cm sIG33(Sf) auf Panzerkampfwagen I Ausf B



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15cm sIG33(Sf) auf Panzerkampfwagen I Ausf B

The 15cm sIG33(Sf) auf Panzerkampfwagen I Ausf B was produced by fitting a 15cm infantry gun on the chassis of a Panzer I Ausf B, protected by a tall boxy superstructure. This example was captured by the Red Army early in 1942.

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SIG 33 auf Geschutzwagen

The sIG 33 auf Geschutzwagen became several combat tank-based mobile howitzer platforms for the German Army in World War 2. This collection of Self-Propelled Artillery (SPA) expedients evolved along with the availability of the various tank chassis used throughout the conflict. At their core, the vehicles fielded the sIG 33 infantry howitzer of 150mm (15cm) caliber and were used in the ranged fire support role. The line began with the chassis of the Panzer I Light Tank and were evolved with the Panzer II Light Tank and, lastly, the Panzer III Medium Tank. Another conversion included the Czech Panzer 38(t) series.

The original 15cm sIG 33 heavy infantry guns were short-barreled, towed artillery pieces utilizing a two-wheeled carriage that incorporated a small gun shield, hydropneumatic recoil mechanism, and a horizontal sliding breech block. The weapon entered service in 1927 and was in play with German forces through to the end of the war in 1945. Manufacture of the guns happened through the storied concern of Rheinmetall primarily with additional production encountered under other brands as well - total production became about 4,600 guns by war's end.

Early-war actions by the German Army showcased a need for speed due to the evolution of mechanized warfare - towed artillery systems simply did not keep pace well alongside mobile armored corps which limited fire support tactics during a given assault. This put the focus on making the howitzers more mobile and the decision was made to mate the gun equipment to the existing, outgoing chassis of the Panzer I Ausf. B Light Tank line. The conversion process gave rise to the 15cm sIG33(sf) auf Panzerkampfwagen I Ausf B which also became known under the name of Sturmpanzer I.

The end result was just that, a Panzer I hull and chassis (complete with its running gear) and the sIG 33 series gun (complete with wheeled carriage) fitted over the vehicle - the original tank's turret accordingly removed. To this was added an open-topped, open-rear fighting cabin which essentially was made up of front and side walls. Sloping was only found along the front panel for basic ballistics protection. Overall weight of the new vehicle was 9.4 tons (short) and dimensions included a length of 2.7 meters, a width of 2 meters, and a height of 2.8 meters. Armor protection reached 13mm along the most critical facings and power was provided through a Maybach NL38TR 6-cylinder, water-cooled engine of 100 horsepower. The engine was coupled to a transmission system yielding five forward and one reverse speeds. Operational range was under 90 miles with a road speed up to 25 miles per hour. The crew numbered four and included a driver, commander, and two loaders.

Production of the Ausf. B model totaled just 38 units under Alkett GmbH and examples were available as soon as 1940. Once in action, limitations proved plenty for the vehicle held a high center of gravity making it an awkward and cumbersome battlefield sight. The lack of armor coverage readily exposed the crew to all manner of battlefield dangers as well as inclement weather. Onboard storage space was also at a premium with only three ready-to-fire 150mm projectiles carried. This latter quality required a trailing SdKfz 10 half-track to serve as ammunition carrier and to ferry three of the four crew into battle.

On the whole, the vehicle was an overweight design in which both the frame and motor works were stressed to their limits leading to frequent mechanical breakdowns. However, the sIG33 150mm guns were as lethal as ever, capable of supplying a hefty ranged punch against soft target areas through indirect fire. Range of the weapon reached out to 3.5 miles and a rate-of-fire of four rounds-per-minute could be achieved. The gun carriers saw combat service during the Belgian campaign and then on to the Battle of France (May-June 1940). They then followed with service in the invasion of the Balkans/Greece (April 1941), and the attack on southern Russia (June-November 1942). By the middle of 1943, the vehicles held little battlefield value and were either given up for good or lost through general wartime attrition.

Despite the limitations of the early mark, authorities considered the sIG 33 gun carrier design more or less a success as a quick-to-produce and effective mobile support platform. The 15cm sIG 33 auf Geschutzenwagen II Ausf C (SdKfz 121) (Sturmpanzer "Bison II") followed by mating the howitzer component to the Panzer II light tank chassis and this vehicle first appeared in 1942. Some changes were instituted to help address the failings of the original design such as a lower center of gravity - the roof line now equal to that of the original Panzer II tank. The 15cm sIG 33 FGST Ausf. PzKpfW II (sf) "Verlanget" appeared in 1943 and featured a lengthened and widened hull for better weight displacement. Power to the Panzer II-based marks was through a Bussing Typ GS 8-cylinder, liquid-cooled engine of 155 horsepower.

The most promising sIG33-armed Geschutzwagen vehicle form was a Panzer III-based model - the 15cm sIG 33 Ausf PzKpfW III. The vehicle was under consideration as early as 1941 and, while the medium tank chassis proved more than a viable gun carrier, further work on the line eventually lost steam in that only and only twelve examples were manufactured and these saw service along the Eastern Front.

The most successful of the sIG 33 conversion vehicles was the one based on the Czech PzKpfW 38(t), a design which was taken over by the conquering Germans. The newly-realized model of 1942 became the 15cm sIG 33(sf) Ausf. PzKpfW 38(t) SdKfz 138 "Bison" and SdKfz 138/I "Grille" was its perfected form of 1943. The PzKpfW 38(t)-based systems became the standardized sIG 33 gun carriers of the war and used in the greatest number.


The Name – Not a Sturmpanzer II or Bison II

The correct German Army designation for this self-propelled artillery gun is 15 cm sIG 33 auf Fahrgestell Panzerkampfwagen II (Sf) Sd.Kfz.121/122 or 15cm s.l.G.33 auf Fahrgestell Pz.Kpfw.ll (Sf.).
While undergoing trials, it was sometimes referred to as the 15cm s.I.G.33 B (this was to show it was an upgrade from the prototype SPG, the 15cm s.I.G.33 A, that used the original five wheeled Panzer II tank chassis and had not yet been lengthened).
After World War II, a scale model kit company produced one of the first retail kits of this vehicle. They called it the ‘Bison II’, believing it to be the natural progression for the earlier Bison 1 self-propelled 15cm Artillery Gun based on a Panzer I tank chassis’.
This was wrong. It was never called the Bison II during the war but, after the war, the name Bison II stuck. Museums, historical books and other scale model kit companies continue to call this mobile artillery weapon the Bison II.
Some authors, museums and scale model kit companies also wrongly call it the Sturmpanzer II. A ‘Sturmpanzer’ is a heavily armored assault tank. It’s crew is protected in a fully armored box, that is enclosed on all four sides and has an armored roof. The front armor of this vehicle is thick to enable it to get close to enemy strong points before firing it’s weapon.
This description bears no resemblance to the function and appearance of the German 15 cm s.I.G. 33 auf Fahrgestell Panzerkampfwagen II (Sf) SPG. This vehicle was not designed to advance towards heavily fortified gun emplacements and blow them up whilst under heavy fire. It is only thinly armored and the crew have very little protection.
This vehicle was designed to keep up with the advancing infantry and tanks, but remain behind them, out of harm’s way, and fire shells over their heads at enemy targets.

Notice the spare road wheels strapped to the top of the right track guard on the 15cm s.l.G.33 auf Fahrgestell Pz.Kpfw.ll (Sf.) on the left. (photographer unknown)


SIG 33 auf Geschutzwagen

Authored By: Staff Writer | Last Edited: 04/06/2017 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

The sIG 33 auf Geschutzwagen became several combat tank-based mobile howitzer platforms for the German Army in World War 2. This collection of Self-Propelled Artillery (SPA) expedients evolved along with the availability of the various tank chassis used throughout the conflict. At their core, the vehicles fielded the sIG 33 infantry howitzer of 150mm (15cm) caliber and were used in the ranged fire support role. The line began with the chassis of the Panzer I Light Tank and were evolved with the Panzer II Light Tank and, lastly, the Panzer III Medium Tank. Another conversion included the Czech Panzer 38(t) series.

The original 15cm sIG 33 heavy infantry guns were short-barreled, towed artillery pieces utilizing a two-wheeled carriage that incorporated a small gun shield, hydropneumatic recoil mechanism, and a horizontal sliding breech block. The weapon entered service in 1927 and was in play with German forces through to the end of the war in 1945. Manufacture of the guns happened through the storied concern of Rheinmetall primarily with additional production encountered under other brands as well - total production became about 4,600 guns by war's end.

Early-war actions by the German Army showcased a need for speed due to the evolution of mechanized warfare - towed artillery systems simply did not keep pace well alongside mobile armored corps which limited fire support tactics during a given assault. This put the focus on making the howitzers more mobile and the decision was made to mate the gun equipment to the existing, outgoing chassis of the Panzer I Ausf. B Light Tank line. The conversion process gave rise to the 15cm sIG33(sf) auf Panzerkampfwagen I Ausf B which also became known under the name of Sturmpanzer I.

The end result was just that, a Panzer I hull and chassis (complete with its running gear) and the sIG 33 series gun (complete with wheeled carriage) fitted over the vehicle - the original tank's turret accordingly removed. To this was added an open-topped, open-rear fighting cabin which essentially was made up of front and side walls. Sloping was only found along the front panel for basic ballistics protection. Overall weight of the new vehicle was 9.4 tons (short) and dimensions included a length of 2.7 meters, a width of 2 meters, and a height of 2.8 meters. Armor protection reached 13mm along the most critical facings and power was provided through a Maybach NL38TR 6-cylinder, water-cooled engine of 100 horsepower. The engine was coupled to a transmission system yielding five forward and one reverse speeds. Operational range was under 90 miles with a road speed up to 25 miles per hour. The crew numbered four and included a driver, commander, and two loaders.

Production of the Ausf. B model totaled just 38 units under Alkett GmbH and examples were available as soon as 1940. Once in action, limitations proved plenty for the vehicle held a high center of gravity making it an awkward and cumbersome battlefield sight. The lack of armor coverage readily exposed the crew to all manner of battlefield dangers as well as inclement weather. Onboard storage space was also at a premium with only three ready-to-fire 150mm projectiles carried. This latter quality required a trailing SdKfz 10 half-track to serve as ammunition carrier and to ferry three of the four crew into battle.

On the whole, the vehicle was an overweight design in which both the frame and motor works were stressed to their limits leading to frequent mechanical breakdowns. However, the sIG33 150mm guns were as lethal as ever, capable of supplying a hefty ranged punch against soft target areas through indirect fire. Range of the weapon reached out to 3.5 miles and a rate-of-fire of four rounds-per-minute could be achieved. The gun carriers saw combat service during the Belgian campaign and then on to the Battle of France (May-June 1940). They then followed with service in the invasion of the Balkans/Greece (April 1941), and the attack on southern Russia (June-November 1942). By the middle of 1943, the vehicles held little battlefield value and were either given up for good or lost through general wartime attrition.

Despite the limitations of the early mark, authorities considered the sIG 33 gun carrier design more or less a success as a quick-to-produce and effective mobile support platform. The 15cm sIG 33 auf Geschutzenwagen II Ausf C (SdKfz 121) (Sturmpanzer "Bison II") followed by mating the howitzer component to the Panzer II light tank chassis and this vehicle first appeared in 1942. Some changes were instituted to help address the failings of the original design such as a lower center of gravity - the roof line now equal to that of the original Panzer II tank. The 15cm sIG 33 FGST Ausf. PzKpfW II (sf) "Verlanget" appeared in 1943 and featured a lengthened and widened hull for better weight displacement. Power to the Panzer II-based marks was through a Bussing Typ GS 8-cylinder, liquid-cooled engine of 155 horsepower.

The most promising sIG33-armed Geschutzwagen vehicle form was a Panzer III-based model - the 15cm sIG 33 Ausf PzKpfW III. The vehicle was under consideration as early as 1941 and, while the medium tank chassis proved more than a viable gun carrier, further work on the line eventually lost steam in that only and only twelve examples were manufactured and these saw service along the Eastern Front.

The most successful of the sIG 33 conversion vehicles was the one based on the Czech PzKpfW 38(t), a design which was taken over by the conquering Germans. The newly-realized model of 1942 became the 15cm sIG 33(sf) Ausf. PzKpfW 38(t) SdKfz 138 "Bison" and SdKfz 138/I "Grille" was its perfected form of 1943. The PzKpfW 38(t)-based systems became the standardized sIG 33 gun carriers of the war and used in the greatest number.


15 cm sIG 33 auf Fahrgestell Panzerkampfwagen II (Sf)

Sometimes referred to as the Sturmpanzer II Bison, the 15 cm sIG 33 auf Fahrgestell Panzerkampfwagen II (Sf) was a German self-propelled heavy infantry gun used during World War II. The 15 cm sIG 33 (Sf) auf Panzerkampfwagen I Ausf B built in time for the Invasion of France in 1940 had proven to be too heavy for their chassis as well as enormously tall. The same gun was mated to the Panzerkampfwagen II chassis in an attempt to drastically lower its height while using a stronger chassis. The prototype used a standard Panzer II Ausf. B chassis when it was built in February 1941, but this was too cramped for use. The chassis was lengthened by 60 centimetres (24 in), which required adding a sixth roadwheel, and widened by 32 centimetres (13 in) to better accommodate the gun while preserving its low silhouette. 15 millimetres (0.59 in) plates formed the front and sides of the open-topped fighting compartment, which was also open at the rear. Its sides were notably lower than the front which made the crew vulnerable to small arms fire and shell fragments. Large hatches were added to the rear deck to better cool the engine.

The 15-centimetre (5.9 in) sIG 33 gun, for which 30 rounds were carried, could traverse a total of 5° left and right and used a Rblf36 sight.


Armaments

Main armament

The Sturmpanzer II mounts a s.I.G.33 infantry support cannon, which can fire HEAT or HE rounds. The shell velocity is very slow (240 m/s), so slow that it can be awkward to target moving targets or those at long ranges, especially with HE rounds. The calibre of the gun is 15 cm (150 mm/5.9 in). The Sturmpanzer does not have any other weapons.

The J.Gr.38 HE shell penetrates 61 mm against all armour angles. The 8.6 kg explosive mass ensures that anything that gets penetrated is instantly knocked out or is so badly crippled that a follow-up shot is guaranteed.

  • Note: the HE on this is so powerful that it can even one-shot top rank tanks reliably, but due to the huge mobility disadvantage, this is not recommended unless you know exactly what you are getting yourself into.

The J.Gr.39 HI/A HEAT shell penetrates 185 mm against vertical armour and still has a 4.16 kg TNT equivalent of explosives behind it, giving it effectively 40-45 mm penetration from the explosion splash on top of the HEAT superplastic copper jet penetration. In one of the minor updates, 120 mm and larger HEAT rounds were altered to act more like HE shells to benefit top rank vehicles - tanks such as the Sturmpanzer are unintentional beneficiaries of this change.

150 mm s.I.G.33 Turret rotation speed (°/s) Reloading rate (seconds)
Mode Capacity Vertical Horizontal Stabilizer Stock Upgraded Full Expert Aced Stock Full Expert Aced
Arcade 18 -4°/+40° -1°/+6° N/A 5.28 7.31 8.88 9.82 10.45 19.50 17.25 15.90 15.00
Realistic 3.57 4.20 5.10 5.64 6.00

Ammunition

  • J.Gr.38 (HE): This round is extremely powerful, and can destroy pretty much every tank at the same battle rating as the 15cm sIG 33 B Sfl. It requires only a hit on the tank, underneath it, or in close proximity to be effective. It completely ignores the armour of most tanks you will face, and is very good at destroying a tank in one shot. It is likely that you will knock out several crew members and/or detonate their ammunition. The shell can also hull break lightly armoured vehicles, such as SPAA.
  • J.Gr.39 HI/A (HEAT): This round is effective, just as is the high-explosive round, but unless you are up-tiering the vehicle, the HEAT round is likely a worse choice. It has more penetration, but that penetration is unlikely to be useful at this BR. Plus, the HEAT does not have near as much post-penetration damage as the HE round, meaning you may waste 2 shots on 1 tank, whereas the HE round may have knocked it out in 1 shot. As such, unless you are up-tiering the tank you will not need HEAT, and you should probably only take a few rounds (if any), just in case you run across something like a B1 Bis. Note: The J.Gr.39 HI/A HEAT round can also hull break the lightly armoured SPAA vehicles you will come across at this BR.

Ammo racks

Full
ammo
Ammo
part
1st
rack empty
2nd
rack empty
3rd
rack empty
Visual
discrepancy
18 Projectiles
Propellants
9 (+9)
10 (+8)
5 (+13)
6 (+12)
0 (+18)
0 (+18)
No

How much ammo to carry?

The most logical ammo loadout would probably either be 18 shells or 9 shells. 18 shells would be logical if you expect to be in the battle for a long time where you might run out of ammunition otherwise. If you don't expect to be firing as much or for as long, then you might consider taking only 9 shells. Taking only 9 shells removes all the ammo from the right side of the tank, which could possibly save your life. 9 shells is probably the most balanced ammunition loadout in terms of survivability and endurance. Of course, you can also take an amount of shells between 9 and 18 in order to partially (but not completely) deplete this first ammo rack. This would be useful if the user desires a longer firing time but still wishes for better survivability. At higher BRs 3.0 or more, recommended amount of shells is 18 or any number of them, since even if you ammunition doesnt detonate, you can still be destroyed due to hull break.


Development and history

The Invasion of Poland had shown that the towed sIG 33 guns assigned to the infantry gun companies of the motorized infantry regiments had difficulties keeping up with the tanks during combat. The easiest solution was to modify a spare tank chassis to carry it into battle. A sIG 33 was mounted on the chassis of the Panzer I Ausf. B, complete with carriage and wheels, in place of the turret and superstructure. Plates 13 millimetres (0.51 in) thick were used to form a tall, open-topped fighting compartment on the forward part of the hull. This protected little more than the gun and the gunner himself from small arms fire and shell fragments, the loaders were completely exposed. The rearmost section of armor was hinged to ease reloading.

There was no room to stow any ammunition so it had to be carried by a separate vehicle. When mounted, the sIG 33 had a total 25° of traverse and could elevate from -4° to +75°. It used a Rblf36 sight. The chassis was overloaded and breakdowns were frequent. The vehicle's extreme height and lack of on-board ammunition were severe tactical drawbacks.


The “Bison” – German Mobile Artillery in the Early War

When Poland signed the capitulation act on October 6 th , 1939, the world stood still before the apparent military might of the Third Reich. It seemed as though the Poles, who had put up a fierce fight, never stood a chance against the then-cutting edge military tactics of the Wehrmacht.

But for the Germans, the Polish campaign had been the testing ground for what was yet to come. Having witnessed firsthand the necessity of artillery support during their swift offensives, the problem of mechanizing their artillery units arose.

So the idea of fitting a large artillery gun onto a tank chassis came as natural. This was how the Bison was conceived a mobile artillery unit, capable of keeping up with tanks and motorized infantry, thus providing constant artillery support to advancing forces.

The design involved the chassis of the Panzer I, which was by then produced in mass numbers and was easy to come by. Also, the Panzer I became fairly outdated by late 1940, and spare parts were primarily used for self-propelled guns such as the Bison, or various tank destroyers.

Its main armament was the powerful 15 cm sIG 33 heavy infantry gun, at the time serving as the backbone of the Heer’s artillery units.

An armored superstructure mounted on the Panzer I chassis protected the gun from small arms and grenade shrapnel, but since it was open topped and its rearmost section was completely exposed, it offered little protection for the gunner.

The loader’s protection, on the other hand, was next-to-zero as they would often be exposed to small arms fire while performing their duty.

The 15 cm sIG 33 was a fairly large gun, which demanded much space to be effectively covered by armor. The size of the gun also denied any room for ammunition, so another vehicle had to be employed at all times for carrying the shells.

Even though its rather clumsy design left very little room for ammo and the crew, when it came to flaws and malfunction, space was plenty.

Due to the robust superstructure, the chassis was overloaded and prone to breakdowns. Also, the high silhouette of the vehicle made it an easy target, and the lack of an ammunition compartment led to many practical issues.

Nevertheless, the Bison served its purpose, most notably during the Battle of France in 1940 and the Invasion of Greece in 1941. By 1943, it was already an antique, while facing the dynamic development of armored fighting vehicles on the Eastern Front.

A sIG 33 auf Panzerkampfwagen I in Greece in 1941. By Bundesarchiv – CC BY-SA 3.0 de

Sturmpanzer Bison sIG33 of the 1 Panzer Division, France 1940

Bison I named Bismarck and Cambrai

Bison Western Front 1940

Bison Eastern Front 1942

15 cm sIG33 Selbstfahrlafette auf Pz.Kpfw.I Ausf.B Bison winter camouflage

Bison Eastern Front 1942. By Bundesarchiv – CC BY-SA 3.0 de

Sturmpanzer Bison I C

15 cm sIG 33 Bison of the 1 Panzer Division (sIG Kompanie 704), France 1940

Bison side view

Bison of sIG Kompanie 704 (5th Panzer Division) Greece

Sturmpanzer I Bison self-propelled artillery

15 cm sIG 33 (Sf) auf Panzerkampfwagen I Ausf B

SPG sIG 33 Bison France 1940

Sturmpanzer I Bison F

15 cm sIG 33 named Cambrai

Bison near Rumigny France of the 9 Panzer Division

Bison SFL 15cm sIG 33 SPG of the 7 Panzer Division

Sturmpanzer I Bison France 1940


Conception et développement

L'invasion de la Pologne en 1939 a rapidement démontré que les unités d'infanterie utilisant l'obusier lourd remorqué sIG 33 avaient beaucoup de difficultés à rester au contact de leurs chars durant le combat, ce canon étant très lourd à manœuvrer. La solution la plus simple fut donc de poser un obusier sIG 33 complet (avec roue et bouclier) sur un châssis de Panzer I Ausf. B juste dépourvu de sa tourelle.

Afin d'assurer un minimum de protection au canon et au tireur contre les armes légères et les éclats d'obus, une casemate à ciel ouvert, faite à partir de 3 plaques de blindage de 13 mm soudées sur les côtés du bouclier frontal, était montée autour du canon à l'avant du châssis. La partie arrière sur charnières pouvait être retirée pour faciliter le rechargement, les pourvoyeurs étant par contre complètement exposés durant cette opération. 3 servants ainsi qu'une provision de 3 obus hautement explosifs pouvait être embarqués, le reste de l'équipe devant suivre dans une autochenille avec les autres munitions [ 2 ] , [ 1 ] . Une fois monté, le sIG 33 avait un débattement horizontal possible de 12,5° de chaque côté et une élévation possible de -4° à +75° [ 1 ] .

Le canon et son blindage étant trop lourd pour le châssis, les Sturmpanzer I possédaient une mobilité médiocre [ 1 ] . De plus, sa silhouette élevée et l'absence de possibilité d'emport de munitions se révélèrent très handicapant au combat.

Le canon : Obusier lourd 15-cm sIG 33 exposé au Musée militaire de Belgrade.


15cm sIG 33 (Sf) auf Panzerkampfwagen I Ausf. B 2019-02-03

The Invasion of Poland had shown that the towed sIG 33 guns assigned to the infantry gun companies of the motorized infantry regiments had difficulties keeping up with the tanks during combat. The easiest solution was to modify a spare tank chassis to carry it into battle. A sIG 33 was mounted on the chassis of the Panzer I Ausf. B, complete with carriage and wheels, in place of the turret and superstructure. Plates 13 millimetres (0.51 in) thick were used to form a tall, open-topped fighting compartment on the forward part of the hull. This protected little more than the gun and the gunner himself from small arms fire and shell fragments, the loaders being completely exposed. The rearmost section of armour was hinged to ease reloading.

There was no room to stow any ammunition, so it had to be carried by a separate vehicle. When mounted, the sIG 33 had a total traverse of 25° and could elevate from -4° to +75°. The gun used an Rblf36 sight. The chassis was overloaded and breakdowns were frequent. The vehicle's extreme height and lack of on-board ammunition were severe tactical drawbacks.

Thirty-eight were produced in February 1940 by Alkett.

The file contains the unit and pcx files. Model is not my own creation. Wyrmshadow helped with the animation files. I merely put the pieces together and cleaned up the model for CivIII and added some what if pieces. A big thanks to everyone that helped out!


Watch the video: 15cm sIG 33 Sf auf PzKpfw 38t, Grille Ausf. M (August 2022).