Saturday 16 November 2019

A Barrel Too Long

Rapid growth in power of tank and SPG guns continued throughout WWII. Designers of some nations achieved the increase in firepower through a harmonious increase of gun caliber and barrel length. Other schools of design preferred to keep the caliber, but significantly lengthen the gun. The second approach was very common for German armoured vehicles. This decision had both positives and negatives. It turned out to be not so simple to install long guns on medium tanks. The Panzer IV/70 is a good example of this. An attempt to create a more powerful variant of the Jagdpanzer IV gave the tank destroyer both new abilities and serious problems.

Fishing rod for a medium chassis

The Wehrmacht's Armament Directorate began to think that the 7.5 cm Pak 40 needs a replacement as early as mid-1942. This gun had outstanding characteristics and could penetrate any tank at a medium distance, including the KV-1 and Churchill. However, experience showed that growth of firepower is always followed by growth in armour. The Germans had excellent foresight: in 1944 IS-2 and Churchill VII tanks could only be penetrated by the 7.5 cm Pak 40 and its derivatives at point blank range.

The first experimental PzIV/70 (V). The photo was taken only after the experimental remote controlled machine gun mount was installed.

A potential replacement for the Pak 40 turned up as early as February of 1942. This was a 70-caliber gun designed by Rheinmetall-Borsig engineers. It was designed for installation in heavy tanks, but ended up on the medium VK 30.01 (DB) and VK 30.02 (M). The second of these tanks was accepted into service as the Panther. The same gun, indexed 7.5 cm KwK 42 L/70, was also seen as a potential replacement for the KwK 40 and StuK 40.

However, the attempt to install the 7.5 cm KwK 42 L/70 in a PzIV failed. The gun was too long and its installation required changes to the chassis. Only models of the gun were ever installed. An attempt to use this gun in medium SPGs failed even faster. Designs showed that installing the 7.5 cm Pak 42 L/70 into a StuG 40 or the early Jagdpanzer IV prototype would require major changes to the casemate. Work stopped in early 1942.

The gun travel clamp can be seen in the front. This distinguishes the vehicle from the Jagdpanzer IV.

The issue of using the more powerful gun for arming tank destroyers was raised once more on January 27th, 1944, at a meeting with Hitler. The first Jagdpanzer IV was delivered that month. This SPG was selected as the recipient of the 7.5 cm Pak 42 L/70.

The StuG 40 Ausf.G was a poor choice for two reasons, both design and production. The installation of a new gun would require a major redesign of the casemate and engine deck. Nobody was going to begin altering the vehicles that were in such high demand as is. The Alkett factory was also bombed twice, with heavy damage. The situation was so serious that Alkett had to quickly develop the StuG IV to be able to use chassis produced by Grusonwerk.

Demonstration for Hitler.

Work on modernizing the Jagdpanzer IV began in the spring of 1944. VOMAG took a Jagdpanzer IV with serial number 320162 produced in March of 1944 as a starting point. As the fighting compartment was roomy enough to take the larger weapon, it was not necessary to radically alter the SPG. However, since the 7.5 cm Pak 42 L/70 was not only longer, but also heavier than its predecessor, the gun mount, mantlet, and shield had to be reinforced. The long and heavy barrel had to be affixed using an A-shaped clamp so it did not loosen during off-road driving. The ammo racks also had to be changed, as the new gun had a much longer round. The ammunition capacity decreased from 79 to 57 rounds. In everything else, the Jagdpanzer IV with the longer gun did not differ from a regular tank destroyer.

Production vehicles kept the same machine gun mount as the Jagdpanzer IV.

Hitler was first shown photographs of the new vehicles on April 6th, 1944. He saw it himself on April 20th, during a demonstration arranged for his birthday. Hitler was happy with the vehicle and it was greenlit. The official designation for the vehicle, Panzer IV lang (V), was Hitler's idea, given on July 18th, 1944. In the fall of 1944 it changed to Panzer IV/70 (V). The letter V meant the VOMAG company.

Overloaded front

On May 4th, 1944, the Armament Directorate prepared a document that called for 2020 Jagdpanzer IV vehicles of all types built between April 1944 and April 1945. Meanwhile, the situation with the Panzer IV/70 (V) was going poorly. It is not known if Hitler knew about this, but the Armament Directorate found out that the front of the vehicle was seriously overloaded. This was without the planned increase of the front armour from 60 to 80 mm! As a result of all these changes, the new SPG weighed nearly 2 tons more than the old one.

One of the first production Panzer IV/70 (V)s.

The 6th Department of the Armament Directorate had an idea about the consequences of such overloading. On May 16th, 1944, less than two weeks after the decision to put the vehicle into mass production, the department proposed to alter the running gear. The changes were not great: the front bogeys would be moved 100 mm forward to help with the change in the center of mass. This proposal was rejected. There was nowhere left to move them to.

On August 10th, 1944, the 6th Department proposed that the front armour should be reduced to 60 mm. This proposal was approved, but that was it. All Panzer IV/70 (V) were produced with 80 mm of front armour. The only proposal of the 6th Department that was put into practice was the installation of the remote control machine gun on the roof. This was only done on the prototype. The vehicle went into production without it.

The vehicles were covered in Zimmerit until September of 1944. However, enemy magnetic mines never turned up.

The first 60 Panzer IV/70 (V) were due in August of 1944, with subsequent increase in production: 90 in September, 100 in October, 150 in November, 180 in December, and 200 in January of 1945. The vehicle was supposed to replace the Jagdpanzer IV, but initial production vehicles were very similar to their predecessor. The biggest change was the travel lock. No changes were made in August and September production types. Nevertheless, only 57 were delivered in September, and even fewer in October: only 41.

The Panzer IV/70 retained its muffler until November of 1944.

It would seem that the first complaints about wearing out of the front road wheels started coming in the fall of 1944. It was too late to introduce any radical changes, especially since they would negatively impact the production volume. Starting in October of 1944 the tank destroyers merely received steel front wheels. Zimmerit was no longer used starting in September-October. The Germans did not end up seeing any magnetic mines that it was supposed to protect from. In October the production of the Panzer IV/70 (V) reached the requirement and even surpassed it: VOMAG delivered 104 vehicles out of 100 planned.

Vehicle with serial number 320996 captured by the British. It has no Zimmerit, the front road wheels are fully metallic, the number of return rollers was reduced to 3.

Bigger changes were introduced by the end of 1944. They were partially connected to the metamorphosis of the base chassis, the PzIV Ausf.J. The number of return rollers was reduced to three in early November of 1944. The muffler was also removed around that time. This change was first introduced in the Jagdpanzer IV, but it was much more commonly seen on its replacement. In November the air intake vent disappeared from the brake access hatches, but some vehicles continued to receive left over old hatches. For instance, the vehicle with serial number 320999 on display at Patriot Park has this type of hatch. The design of the rear tow hooks and machine gun mount cover also changed. 

The vehicles also received lightened track links starting with November, which helped reduce its mass. Gutters to prevent rain from seeping through hatches were added in December, as well as a new top cover for the gun sight, which was now made from separate plates. Not all vehicles received it.

The Panzer IV/70 (V) received straight exhaust pipes instead of mufflers starting in October-November of 1944.

The rate of production of the Panzer IV/70 (V) remained high in late 1944. The plan was overfulfilled again in November: 178 vehicles were delivered instead of 150. 180 were produced in December. However, in January only 185 instead of 200 were built. This shortfall was caused by the growing agony of the German tank industry. The factory suffered from shortages of parts and electricity. In February 135 vehicles were delivered instead of 160. Somewhere around this time, some of the vehicles began to receive cast idler wheels. A simplified travel lock was used starting in early 1945. The periscopic sight received a visor to protect it from lens flares. The rangefinger mount was also changed.

These vehicles were produced in February-March 1945.

Production continued until March of 1945. Starting with March 19th, Plauen, the city where the VOMAG factory was located, was heavily bombed. On March 23rd the factory was destroyed completely. 50 out of the 180 planned vehicles were delivered that month. On that, production stopped. In total, VOMAG produced 930 Panzer IV/70 (V) with serial numbers in the 320651–321000 and 329001–329699 ranges.

An ersatz from Alkett

Despite the overloaded chassis and issues with front wheels, the Panzer IV/70 (V) was not a bad vehicle. At the very least, it was hard to produce anything better given the strict requirements that German designers were given. Nevertheless, the Panzer IV/70 (V) was not the only SPG on the PzIV chassis that received a Pak 42 L/70. The aim of increasing the volume of production led to the creation of another.

Prototype of the Panzer IV lang (A) mit 7,5 cm Pak 42 L/70.

The PzIV received its double due to the unsettling conclusions that the Germans made when studying a captured IS-2 tank. The new Soviet tank had thick armour that the 75 mm KwK 40 L/48 could penetrate only at point blank range. On June 24th, 1944, Alkett received an urgent order to install the 75 mm Pak 42 gun into the PzIV. The idea to install it in the turret was doomed to fail, as the chassis would be seriously overloaded. On July 5th, 1944, an idea was proposed to install the Panze IV/70 (V) casemate on top of the turret platform. The result was heavier than the Panzer IV/70 (V), but it could be made quickly and without changes to the base chassis.

Hitler inspects the band-aid solution.

On July 6th an experimental prototype of the Sturmgeschütz auf Pz.Kpfw.IV Fahrgestell was shown to Hitler, who approved the design. In any other conditions it would have been hard to find this proposal satisfactory. The casemate was 38 cm taller than the PzIV/70 (V). However, the overall height was only 2.2 meters, about the same as the StuG 40 Ausf.G. The mass, however, was much higher: 27 tons. On paper, the top speed was 37 kph. The power to weight ratio dropped to 10 hp/ton. It was hard to call the tank destroyer agile. Nevertheless, an alternative to the VOMAG design was born.

Unlike production vehicles, the Panzer IV/70 (A) prototype had its sides made from two parts.

In August of 1944 the SPG received the name Panzer IV lang (A) mit 7,5 cm Pak 42 L/70. However, the index introduced in November of 1944 is much better known: Panzer IV/70 (A). The letter A stood for the developer: Alkett. A different company ended up producing it, since Alkett was overloaded with orders for the StuG 40 Ausf.G.

It was easiest to build the vehicle on a PzIV chassis at a factory that already produced the PzIV. The order was given to Nibelungenwerk, the main producer of the PzIV. At a conference on July 6-8th, 1944, Hitler ordered a change to the production plan. 50 SPGs were planned in August, 100 in September. If Nibelungenwerk's capacity allowed, the factory would begin producing 150 vehicles per month starting in October 1944.

A production variant of the vehicle.

These plans never came to pass. Nibelungenwerk delivered its first Panzer IV/70 (A) in August, but only 3 instead of 50. Production vehicles were different from the prototype. The side of the casemate was built from one sloped plate. The protection of the machine gun also changes. It quickly turned out that the chassis needs the same changes as the Panzer IV/70 (V) chassis. Significant overloading, especially of the front, led to frequent breakdowns of the road wheels.

The first two bogeys on each side were equipped with all steel road wheels starting in September of 1944. On September 18th, new mesh skirts entered production. They were much lighter than the old ones, but offered the same protection from anti-tank rifles. Zimmerit was no longer applied starting in September of 1944. No photos of the initial production vehicles exist, but there were not so many of them built. Nibelungenwerk only built 60 vehicles in all of September.

Panzer IV/70 (A) with mesh skirts.

Production in Saint Valentin lagged behind the quota in the following months. 43 were delivered in October of 1944, 25 in November. The reduction is linked to damage dealt to the factory on October 26th by Allied bombers. In December of 1944 the plan for Nibelungenwerk was reduced to 80 Panzer IV/70 (A) per month, and the factory almost met it, delivering 75. In January of 1945 the order decreased to 50 tank destroyers. This was the only month when Nibelungenwerk met its quota.

The rear tow hook was changed in December, and this was the month when the number of return rollers was reduced to 3 per side.

This vehicle is showing its attachment to fire from a curved barrel StG.44.

20 Panzer IV/70 (A) were built in February. Production was no longer planned in March, but Nibelungenwerk assembled its last vehicles from its stocks. In total 277 Panzer IV/70 (A) with serial numbers 120301–120577 were built. The Panzer IV/70(A) was the last German wartime SPG to be put into mass production.

Some late model vehicles also had an unusual type of defensive armament: a StG.44 assault rifle with a curved barrel that the loader could fire through his hatch.

Further work performed by Krupp to improve the Panzer IV/70 (A). This project was never seriously considered, as the chassis was overloaded as is.

To finish, let us mention a variant of the Panzer IV/70 (A) that was never built in metal. In late 1944 Krupp proposed a number of projects to re-arm existing vehicles with more powerful weapons. The Panzer IV/70 would receive the 88 mm Pak 43 L/71. This gun could defeat any tank or SPG of the Allies, but the project was rejected. The gun would push the mass of the already overloaded SPG to over 30 tons.

Tank destroyers under questiong

The Panzer IV/70 (V) was used in the same way as the Jagdpanzer IV. Unlike the StuG 40, these vehicles were not used in assault gun brigades, but as reinforcements of tank, panzergrenadier, and SS divisions. The first vehicles were sent to tank brigades (105th to 110th). The TO&E specified that the tank battalion of this brigade had three companies of Panther tanks and a company (battery) of 11 Panzer IV/70 (V).

An early Panzer IV/70 (V) produced in August-September 1944, captured by the British.

The Panzer IV/70 (V) was used en masse in tank destroyer battalions. The 560th tank destroyer battalion was the first to receive 33 of them on October 6th, 1944. The Panzer IV/70 (V) was also used in the 655th (37 units), 519th (9), 559th (18), 563rd (31), and 510th (10) battalions.

In late March of 1945 one Panzer IV/70 (V) was sent to the 241st Assault Gun Brigade, and on February 10th 10 were sent to the 303rd Tank Battalion.

The Panzer IV/70 (V) was often used by SS units. Usually they received battalions composed of two batteries (10 vehicles each plus a commander's vehicle, 21 in total). Towards the end of the war this structure broke down. Any available vehicle could be sent to any unit to refill it or be sent to plug a hole.

A vehicle from the 12th SS division during the counteroffensive in the Ardennes, late 1944.

The difficult situation on the front lines had an impact on the use of the vehicles in battle. Loss of most of France cut the Germans off from their rear line training bases where units could prepare and organize. Now units were often sent to the front lines with little knowledge of their vehicles. The most new crews could hope for were brief courses on driving and shooting.

The finale of the battle for the Ardennes.

Even in these conditions and despite the overloaded chassis the Panzer IV/70 (V) could be a dangerous enemy for medium tanks. The 7.5 cm Pak 42 L/70 could penetrate enemy tanks from 1.5-2 km, while American 76 mm and Soviet 85 mm guns could penetrate its front only from 100-200 meters. Even the issues with quality of the Czech steel that these SPGs were built from did not help much.

In August of 1944 production of the IS-2 with a straight upper front plate began. This armour was too great for the gun of the Panzer IV/70, but the front of the turret could still be penetrated from about a kilometer away.

ISU-122, ISU-152, and SU-100 SPGs could also successfully combat the Panzer IV/70 (V).

Often only the very first road wheel was all metal, rather than the first two.

The Panzer IV/70 (V) was a dangerous opponent on the defense. The biggest problem was that an SPG had to move as well as shoot. Here is where the German tank destroyer fared poorly. German production plans made in February of 1945 continued production of 200 vehicles at VOMAG from April to May, then 150 from July. These vehicles would then be phased out for something more suitable, as the situation with their mobility and reliability was critical. However, Allied aircraft corrected these plans by destroying VOMAG.

Canadian trophies. One of them is currently on display at Base Borden.

Issues with the mobility and reliability of the Panzer IV/70 (V) were nothing compared to what was happening with the Panzer IV/70 (A). The first vehicles of this type were supposed to be sent to the front in September, but did not arrive there until mid-October. These tank destroyers were to be assigned as reinforcements to units that used PzIV tanks. At first, that was the case: 17 vehicles each were sent to the 3rd, 17th, and 25th tank divisions, 4 SPGs to the 13th tank division, and 13 in the 24th tank division. Towards the end of the production run the Panzer IV/70 (A) were sent to assault gun brigades in penny packets.

This vehicle was destroyed in combat around Berlin.

The opinion of the German command about this vehicle can be seen in the production plans made in February of 1945, where it is no longer present. Nibelungenwerk was freed from having to produce them. It was planned that production of the Panzer IV/70 (V) would be set up there.

The situation with the protection of the Panzer IV/70 (A) was interesting. Even by German data, it was significantly inferior to the Panzer IV/70 (V). For instance, the T-34-85 could destroy it from 1.5 kilometers. The front of the SPG was vulnerable to even British and American 75 mm guns. However, the Panzer IV/70 (A) often fell victim not to the enemy's guns, but to its own reliability. Even the Sturmpanzer assault gun weighed less than this band-aid solution.

A Panzer IV/70 (A) destroyed in battle with French forces. It is currently on display at the Saumur tank museum.

Some vehicles, captured by the Red Army, were issued to Bulgaria. One of them, with serial number 320662, is on display at the military museum in Sofia. Unlike the Jagdpanzer IV, the Panzer IV/70 (V) did not enjoy post-war service. The overloaded and unreliable vehicle was not needed. As a result, only five of the 930 tank destroyers produced survive to this day. Only one Panzer IV/70 (A) survives. This SPG with serial number 120539 was knocked out by French tanks in the winter of 1945, but retained its mobility. It was included in the French army, and later sent to Saumur, where it remains on display.

The SPG was put back into running order fairly quickly.

After the war the idea of creating a tank destroyer with a low silhouette remained. The Bundeswehr created the requirements for a similar vehicle in the late 50s, which gave birth to the Kanonenjagdpanzer tank destroyer. The Germans learned the lessons of WWII well, and the post-war tank destroyer had little to do with the Jagdpanzer IV, let alone the Panzer IV/70. The Bundeswehr sacrificed thick front armour and an excessively long gun in exchange for mobility. The Kanonenjagdpanzer remained in service in various nations until 1990. The mass of the Kanonenjagdpanzer was 27.5 tons, even heavier than the Panzer IV/70 (A).


  1. If you want fail look to the SU-100. It had a heavier and longer gun and front armor than the SU-85. A friends co-worker drove one in the Czech Army and said it was a nightmare as it was nose heavy.
    Incidentally the Panther was considered a heavy tank.

    "The number of road wheels was reduced to three in early November of 1944." What? Maybe they mean idler jacks?

  2. I find it oddly amusing how the proposed IV/70 (A) with the 8.8 cm gun looks like nothing so much as a pocket ISU-122.