Saturday 8 August 2020

The Best StuG

The StuG III and StuG 40 were the most numerous armoured vehicles in the German army during WWII. Together with the StuH 42 assault howitzer, 11,300 such vehicles were built. The front lines needed more of these assault guns, and so Germany began to develop these vehicles on other chassis. The fighting in 1942-43 made it clear that the Marder tank destroyers needed to be replaced. The Wehrmacht wanted something lower and better protected. This began the development of the main character of today's article, the Jagdpanzer IV tank destroyer. The sum total of its characteristics made this vehicle the best German medium SPG of the war.

An alternative from VOMAG

The StuG did not become common immediately. These vehicles were primarily meant for infantry support and went to artillery units, not tank ones. The StuG could be considered a "budget Pz.Kpfw.IV": the tank without armament cost 103,500 Reichsmarks, while the StuG without armament cost 82,500.

The situation changed in late 1942. The 7.5 cm StuK 40 L/43 made the StuG an effective countermeasure to Soviet tanks, even the well protected KV-1. Later the 48 caliber version was developed. In late 1942 the monthly production rate of StuGs finally surpassed 100 vehicles, and in December of 1942 the most numerous vehicle in the history of German armour came to life: the StuG 40 Ausf.G. MIAG joined Alkett in producing the StuG 40 in February of 1943. Together, these two companies produced as many as 300-350 StuGs per month.

A model of the kleine Panzerjäger der Firma VOMAG in its initial configuration.
The Pz.Kpfw.IV received a similar long barrelled 7.5 cm KwK 40 L/43 gun as the StuG. Unlike the Pz.Kpfw.III Ausf.K, which remained on paper, the Pz.Kpfw.IV with long guns went into production. The first tanks of this type called Pz.Kpfw.IV Ausf.F2 were built in March of 1942. In July they were renamed Pz.Kpfw.IV Ausf.G. 1927 Pz.Kpfw.IV Ausf.G were built until June of 1943.

The increase in Pz.Kpfw.IV production took place even before such an increase with the StuG. In addition to Grusonwerk, VOMAG began building the Pz.Kpfw.IV Ausf.F in August of 1941, and the Austrian Nibelungenwerk company joined in during November of 1941. The latter was built especially to produce the Pz.Kpfw.IV, and in June of 1944 it turned out to be the only factory still making this tank. VOMAG  (Die Vogtländische Maschinenfabrik AG) was a major producer of trucks and buses before the war.

VOMAG never built tanks until 1941, but in 1942 they completely stopped building trucks. This allowed the factory to double its output in tanks by 1943.

The sloped armour improved the protection of the casemate compared to the StuG.

By September of 1942 the armour of armoured vehicles needed to be increased as well as the armament. One of the consequences of this was the development of the Pz.Kpfw.IV Ausf.H or the 9.Serie/B.W. This tank was supposed to get sloped front and side armour, but the idea had to be discarded as the mass of the modernized tank increased to 28.2 tons. The idea of installing the 75 mm KwK 42 L/70 into the turret also ended up failure.

The work on improving the characteristics of SPGs went on in parallel. An SPG with the L/70 gun on the chassis of the Gefechtsaufklärer Leopard was developed in the fall-winter of 1942. Alkett received an order for modernization of the StuG III in December of 1942. The new StuG would have a 7.5 cm KwK 42 L/70 gun and sloped casemate armour. This work only reached the full sized model stage, completed in 1943. Later the work was applied to the Jagdpanzer 38 project.

The final version of the project being shown to Hitler on May 14th, 1943. The model had front facing machine guns and a new driver's observation device.

Only VOMAG reached the prototype stage. The requirements they received were similar to those received by Alkett, the only difference is that the Pz.Kpfw.IV Ausf.F was used as a chassis. The SPG initially used an L/70 gun, but the requirements later changed. Such a long gun would have inevitably overloaded the front wheels, as happened later with the Panzer IV/70.

The final requirements listed the 7.5 cm Pak 39 L/48. This gun was a 7.5 cm StuK 40 L/48 with a different mounting. The StuG's gun was installed on a pedestal mount, while the 7.5 cm Pak 39 L/48 was held on a frame. This reduced the mass of the system and improved protection. The frame allowed the designers to get rid of the bulges in the casemate that were a big weakness of the StuG. 

The first experimental  Panzerjäger aus Fg.St. Panzer IV at the factory, October 1943.

The casemate turned out to be rather original. The sides were sloped in addition to the front. The front armour, sloped at 40 degrees, provided the equivalent of 110 mm of protection at 90 degrees. The sides installed at 60 degrees were 40 mm thick. Unlike the StuG, the width of the casemate was equal to the width of the entire vehicle. The sponsons were used to store ammunition, as a result of which the SPG fit 79 75 mm rounds.

The rational layout resulted in the SPG being lower than the StuG, which was not that tall to begin with. The kleine Panzerjäger der Firma VOMAG was only 1.7 meters tall.

This design also had its drawbacks. Instead of a commander's cupola, the commander just had a rotating periscope in his hatch with two more periscopes looking forward and to the left. However, a cupola could have also added an extra weakness.

The prototype had thicker front armour than the model.

Requirements for the SPG were approved in February of 1943. A model built on the chassis of a Pz.Kpfw.IV Ausf.F was ready in the spring. The wooden casemate had interesting features: rounded joints of the front and sides. Some changes were implemented after the model was built. The driver's observation device was changed. Defensive armament was added: two MG 42s in the front plate covered by conical shutters. They were only useful for scaring off enemy infantry, but this was better than nothing. This was the form in which the kleine Panzerjäger der Firma VOMAG was shown to Hitler.

The gun mantlet was modified, but this was still not the final variant.
The project continued to evolve. The front of the hull was changed. Even the thickened front of the Pz.Kpfw.IV Ausf.G turned out to be vulnerable to guns bigger than 76 mm. As the mass of the vehicle already threatened to cross reasonable limits, the solution was slightly unexpected. Instead of one 80 mm plate at 78 degrees, two were used: the upper was 60 mm thick at 45 degrees, the lower was 50 mm thick at 35 degrees. The horizontal part with transmission access hatches remained. The medium SPG maintained protection comparable to that of a heavy tank at a mass of only 24 tons.

A demonstration of the Panzerjäger aus Fg.St. Panzer IV to Hitler on October 20th, 1943.

The first experimental prototype was named Panzerjäger aus Fg.St. Panzer IV (tank destroyer on the Pz.Kpfw.IV chassis). It received a new gun mantlet, an even larger one. As an aside, the name of the SPG changed at least three times in 1943 alone. The new vehicle also received side skirts. Unlike the skirts used on the Pz.Kpfw.III, Pz.Kpfw.IV, and StuG 40, these only covered the running gear. They were an addition to the spaced armour initially used to cover the engine compartment.

Hitler inspected the prototype on October 20th, 1943. Permission was given to put it into production.

Tank destroyer with room to spare

The acceptance of the Panzerjäger aus Fg.St. Panzer IV into service was timely. British and American bombers began to make their own corrections to German manufacturing programs in the spring of 1943. The Alkett factory was bombed on November 26th and 28th. The work in Spandau froze and a reserve production base for SPGs was urgently needed. This is where an SPG with a superior design to the StuG 40 came in very handy. 

The second prototype, November 1943. This vehicle was later used for training.

Factories which built the Pz.Kpfw.IV tank, including Grusonwerk, were pressed into building SPGs after Alkett was bombed. One could expect that Grusonwerk would start building VOMAG's design, but instead they quickly developed the StuG IV, a hybrid of the StuG 40 casemate and Pz.Kpfw.IV chassis. A "centaur" with the Pz.Kpfw.IV chassis and a Panzer IV/70(V) chassis called Panzer IV/70(A) was also developed at Alkett. Production of the Panzer IV/70(V) began in August of 1944.

The situation was bordering on the absurd. Between August and November of 1944 the Germans were producing five different SPGs on three different chassis in the same weight class with 75 mm guns. This is not including the Jagdpanzer 38, a budget alternative to the StuG 40.

This vehicle survived the war and can now be seen at the Munster tank museum in Germany.

VOMAG was the only factory that managed to design a good vehicle, however it was not immune from the "wonders" of German tank industry. The Armament Directorate couldn't think of anything better than to order the armour from VHHT (Vítkovické horní a hutní těžířstvo, modern day Vítkovice Steel) in Ostrava, Czechia. This was clearly a poor move. The brittle nature of Czech armour was known even before WWII, and the arrival of the Germans did nothing to fix this. The protection of the German SPG dropped before it even went into production.

The difference in quality was seen when hit by 85 mm shells and larger. Pretty graphs shown in many books should be treated with scepticism, as the penetration displayed is almost always theoretical. In practice, the armour of German SPGs often behaved very differently.

The roof of the second prototype. Like on the first production vehicles, the bomb thrower port is plugged.

Delays with hull production were the limiting factor. Plans made in June of 1943 called for the delivery of 10 vehicles in September of 1943, 20 in October, 30 in November, and 40 in December. In practice, the second prototype was only finished in November. The hull changed little, but the gun mantlet was noticeably different. The vehicle received a coat of Zimmerit.

The mess with indices led to the vehicle being named Panzerjäger 39 mit Pak 39 kal. 7,5 cm L/48. This name later transformed into a rumour of an E-39 tank destroyer, which never existed. There was also a version of the SPG with 6 road wheels per side based on the Pz.Kpfw.III/IV chassis. It was redone several times but never built in metal.

The production vehicle received the name le.Pz.Jg.IV in January of 1944. Work on production SPGs began in December, but they were slightly different. The rounded joints had to go, and there were issues with cast components. Although VOMAG received 46 hulls and 25 turret platforms by the end of 1943, only 10 le.Pz.Jg.IV were built and none were delivered to the customer.

One of the first le.Pz.Jg.IV produced in January-February 1944.

Issues with hulls continued to slow down production. The plan was to build 50 vehicles in January, 60 in February, 90 in March, 120 in April, and 140 in May. In practice, only 30 were finished in January of 1944, 10 of which were the ones built in December. 45 were delivered in February, 75 in March and 106 in April. The supply issues were not just with hulls. There was supposed to be a bomb thrower in the roof, but no vehicles built in January had one, as they were not delivered. They did begin arriving later, but a part of the vehicles never had them.

Design changes were introduced after experience was gained.

The vehicle continued to change even after it was put into production. Initially, spare tracks were attached to the upper front plate, but they were moved to the back as of February 1944. Attachments for two spare road wheels were installed on the engine deck. The machine gun port on the left of the front plate was removed, as there were many issues with that mount, and the opening was welded shut on those hulls where it was cut.

An attempt to improve the commander's vision. Trials of this improvised commander's cupola had poor results.

The right hand machine gun mount used by the loader was also pretty pointless, but it seemed like a bad idea to leave the SPG without any defensive armament at all. Experiments with alternative armaments began in the spring of 1944. In March-April a number of vehicles were equipped with remote control machine gun turrets, but these proved poor. The right machine gun port remained.

An attempt to install a remote controlled machine gun also failed.

Another issue with the le.Pz.Jg.IV was poor visibility from the commander's station. His observation devices were insufficient for proper vision. SPG #320036 was used to test a semblance of a commander's cupola with a rotating periscope in one of the hatch flaps. Trials held in April of 1944 showed that the results were mixed. The commander's vision improved, but there was still an impressive dead zone. A decision was made to keep the hatch as is.

The third issue was easily solved. Firing the gun raised a large cloud of dust due to the gases coming out of the muzzle brake. The muzzle brake was removed from the le.Pz.Jg.IV in April-May of 1944. A reinforced recoil brake cylinder was added to compensate.

A plug was welded over the left hand machine gun port in March of 1944 when the le.Pz.Jg.IV lost its second machine gun. After the hulls with this port were used up, it vanished.

90 vehicles named Panzerjager IV (Sd.Kfz.162) were built in May of 1944. By the spring of 1944 it was clear that 60 mm of front armour was not enough. The thickness was increased to 80 mm starting with vehicle #320301. The diameter of the machine gun port cover was increased at the same time. The mass of the SPG increased slightly.

The Panzerjager IV from May to September of 1944.

Production of the Panzerjager IV reached planned levels only in the summer of 1944. Cessation of production of the Pz.Kpfw.IV at VOMAG helped. As planned, 120 Panzerjager IV were completed in June. In July, 125 were built out of 130. This was the peak of production.

The idea to install an L/70 gun into the SPG remained, and the result was the Panzer IV lang (V). Production began in August of 1944, but production of the Panzerjager IV continued since there was a backlog of parts. 92 vehicles with L/48 guns were finished with a plan for 80.

A destroyed Jagdpanzer IV from the 11th Tank Division. After September of 1944 Zimmerit was no longer applied.

The Panzer IV/70 (V) and the older vehicle that changed its name to Jadgpanzer IV Ausf.F in September were produced in parallel. The last changes to the Jagdpanzer IV were introduced in September. Straight exhaust pipes with flash suppressors replaced the muffler. They had a big drawback: water could enter the vertical pipes during rain. Because of this, special attachments were installed.

Additionally, the Germans finally figured out that the Red Army had no magnetic mines. Application of Zimmerit ended. 38 Jagdpanzer IV were built in September, 46 in October, and the last two were delivered in November. A total of 769 Jagdpanzer IV were built (not including the 2 prototypes). Production vehicles received serial numbers ranging from 320001-321000. This range also includes 231 Panzer IV/70.

Support for tank divisions

The StuG III and StuG 40 were sent to assault artillery battalions that were subordinate to infantry units. This was not the case with the Jagdpanzer IV. Even though its characteristics were very similar, the Germans had another task in mind. It was meant to replace the Marder II and Marder III tank destroyers, especially in tank divisions. These vehicles worked well as tank destroyers, but they were too small and had very thin armour.

A vehicle from the Panzer Lehr division, January 1944 production.

The first 45 Jagdpanzer IV were issued in February of 1944. The first recipient was the Panzer Lehr division. The Jagdpanzer IV were supposed to be issued in anti-tank batteries within anti-tank battalions. According to TO&E KStN 1149 issued on February 1st, 1944, a battery could include 10 or 14 SPGs. 14 SPGs were sent to the 2nd Tank Division in April of 1944. 12th SS division Hitlerjugend received 10 in April of 1944, as did the 6th and 19th Tank Divisions in July of 1944.

The Panzer Lehr received 31 vehicles. Initially they expected to form a battery of 14 Jagdpanzer IV and 14 Jagdtiger, but heavy tank destroyer production stalled. The result was a new type of formation: a tank destroyer battalion. 4 vehicles were included in the HQ and 9 more spread out across three batteries.

The most common unit to use this vehicle was the battalion with 2 batteries of 10 each and a commander's vehicle (21 in total). The aforementioned 2nd Tank Division received such a battalion. In addition to the initial 14 SPGs they received another 7. The 12th SS, 6th, and 19th Tank Divisions eventually received 11 additional vehicles to form a 21-SPG battalion. Battalions containing 21 Jagdpanzer IV were also issued to Panzergrenadier divisions within both the Wehrmacht and the SS.

An SPG from the Hermann Goering division lost in Italy. A penetration next to the driver's vision port can be seen.

Even though the first Jagdpanzer IV arrived in March of 1944, they were not used in battle for some time. The vehicles were attached to units are they arrived either in France or in the deep rear on the Eastern Front to refit. The Luftwaffe field divisions, namely Hermann Goering, were the first to use these vehicles in battle. This happened on May 24th, 1944, in Italy. The division had 21 Jagdpanzer IV. By June 1st 5 vehicles were permanently lost and only 9 remained by July 1st.

An almost complete battery of assault guns. In battle the skirt armour was often removed, since it got in the way when driving on difficult terrain.

Judging by diagrams that migrate from book to book, the front armour of the Jagdpanzer IV was immune to American 75 mm guns, and the 76 mm guns used on the M10 and M18 tank destroyers could only penetrate them from 100 meters.

The result of the fighting in Italy was somewhat different than the diagrams would suggest. A number of these vehicles were penetrated frontally, and it was unlikely to have been from point blank range. Theoretical calculations are often different from practice.

Similar penetrations can be seen in vehicles lost in Normandy. The aforementioned Panzer Lehr initially fought very well and lost only one vehicle. Fortune came up short in July, when total losses numbered 19. American GMCs and now even Sherman tanks penetrated the front of the Jagdpanzer IV with envious regularity.

A captured vehicle from the Panzer Lehr.

This problem was solved only by thickening the front armour of the vehicle to 80 mm, but this helped only partially. The information that the D-25 gun in the IS-2 heavy tank could only penetrate the Jagdpanzer IV from 600 meters looks laughable, as the D-25 could penetrate the Panther (the same 80 mm at a similar angle) from a range of up to 2.5 km.

The thickening of the front armour did not rid the Jagdpanzer IV of all of its weaknesses, as the machine gun port and the driver's vision block remained. A hit to the vision block was often fatal for the SPG and its crew.

The Jagdpanzer IV played an active role in the Adrennes counteroffensive. A vehicle from 12th SS division Hitlerjugend is pictured.

Despite its issues, the Jagdpanzer IV was one of the best medium SPGs on both sides of the front in the summer of 1944. Of course, the poor quality of armour reduced the effectiveness of the frontal protection, but context is key. The Jagdpanzer IV's peers, the GMC M10 and SU-85, had similar guns but thinner armour, especially from the sides. Another advantage of the Jagdpanzer IV was the low silhouette, an important factor for a tank destroyer. The mobility also remained at the level of the Pz.Kpfw.IV, which was sufficient.

If one treats the Jagdpanzer IV as a replacement for the Marder III, then VOMAG's designers did their jobs well. The problem was with the German leadership who decided to produce these vehicles at VOMAG alone. It was the Jagdpanzer IV and not the Jagdpanzer 38 that could have made the work of Soviet, American, and British tankers much more difficult in the concluding period of the war.

The result of fighting in the Ardennes. Judging by the rings on the barrel, the crew claimed no fewer than 3 American tanks.

A second mistake was the replacement of the Jagdpanzer IV with the Panzer IV/70(V). This SPG deserves a separate article. Here, let's just say that the L/70 gun was not the best option. The new gun came with a whole bundle of issues, including overloading of the front wheels and a drastic drop in mobility. The "fishing rod" was also excessive when it came to fighting medium tanks.

The fact that this was a mistake is highlighted by post-war use of VOMAG's SPGs. The Panzer IV/70 was hardly used anywhere (a few vehicles were used by the Bulgarian army), but the Jagdpanzer IV's career was much more interesting. 15 of these SPGs were used by Bulgaria, one of them survived to this day as a pillbox. 6 vehicles sold by the French to Syria lived interesting lives and were last used in battle in 1967. The remains of one of Syria's Jagdpanzer IVs still gather rust on Golan Heights.


  1. Hmm, the SU-85M's frontal armor protection was superior, as was its mobility and gun, I believe.

    I know I've been on a 'what if' tear on your blog of late, but to me instead of the 75L/70 Kwk42, was there any notion of sticking the Kwk36 on this vehicle? You'd lessen the overhang issues of the Kwk42, plus the Kwk36 is a nice compromise between AT and HE capability. I wonder why no SPG carried it.

    1. I don't think so, but I'll defer to Yuri's much greater insight here.

    2. Purely speculating here but probably internal space considerations? IDK how much size difference there was between those guns at the breech end, but if nothing else you could fit in more 75 mm ammunition and if the vehicle was intended primarily as a tank-killer instead of assault gun the long 75 was probably the better tool for the role.

      If I were to further speculate as to why the "short" 88 saw no SPG use (or for that matter much AFV use period, the Tiger aside) I'd hazard there probably wasn't much point - any casemate that could comfortably accept it could likely equally take the beefier Pak 43 without too much trouble while the various 75 mm jobs were a better fit for anything smaller. No real reason to take the middle ground there then.

    3. I guess we differ again. Kellomies. The 75 mm Kwk42 is such a specialized weapon that the only thing I'd put it on would be a Marder-or Nashhorn-like chassis (to make it a mobile AT weapon). Stugs by contrast ended up being general-purpose weapons in actual usage, so why not a good general purpose gun?

    4. ~75 mm WAS pretty general purpose tho (there's a reason just about all the "workhorse" medium tanks of the war carried it), and IIRC the Germans were clever enough to use reduced propellant charges in the HE/frag shells of their high-velocity version so they didn't have to compromise explosive payload with thicker cases, too (unlike eg. the Americans whose 76 mm ended up with a pretty nerfed HE round because of that AFAIK).

      Also compact enough to fit in an awful lot of stuff and widely used in various towed guns so besides payload considerations there was probably also an economic-industrial argument going for it. The Panther, intended to become the next standard line tank, being fitted with one was certainly one strike in favor of using it more widely in other "standard issue" designs so as to streamline logistics - after all, God knows the insane hodgepodge of trophy kit in the German arsenal was already enough of a raging supply headache.

    5. Even then, Kellomies, Kwk42 round has *slightly* less HE punch than the Pak40,despite the reduced propellant charge. So all you get is more AT capability. Putting the Kwk36 on this vehicle would increase both the HE and the AT capability.

      Stugs were distributed to infantry divisions as anti-tank assets, but they were also used to support infantry operations. (Studies have shown that even if you have a few AFV, or even ONE, and the other side does not, in an infantry-vs-infantry contest one's own casualties drop dramatically). One of the things that drove the IS and ISU line of vehicles was that the Soviets found that even their 85 mm HE rounds were insufficient against infantry fortifications.

    6. German design philosophy seems to have generally tended towards favoring ammunition capacity and rate of fire over bigger boom - "two smaller shells achieves more than a single somewhat bigger one" kind of logic I suppose, which is valid enough for most purposes.

      They also had a parallel evolutionary line of Sturmhaubitze (assault howitzers - compare the Allied practice of howitzer-armed "close support" medium tank variants) for when bigger bang was desired, taken to a typically absurd logical conclusion with the Sturmtiger and its ridiculous 38 cm rocket mortar. The early rather ad-hoc ones (cough Sturmpanzer I cough) aside though these mostly entered service in or after '42 when the tide was already turning and the Germans did ever less assaulting on fortified positions as opposed to trying to hold their own ones and contain massive armoured breakthroughs of the same.

      Small wonder then that the Soviets were the ones putting serious effort into fortress-smashing heavy assault guns (the Democracies seem to have preferred heavy conventional artillery and the occasional artillery SPG for bunker-busting instead) while the Germans mostly let such fall by the wayside as increasingly unnecessary in the wider strategic context and instead prioritised the ability to make holes in hostile metal boxes. (Which was then taken into *another* absurd white-elephant conclusion in the Jagdtiger but that's Nazi Germany for you.)

      Also pretty sure the 88L56 had no meaningful advantages over the 75L70 in AT work. AFAIK the penetration characteristics were about the same but the latter shot faster and flatter and could carry more ammo in a given amount of space, so.

      Idle speculation but there may have also been industrial-political considerations involved. The 88 mm was after all primarily an AA caliber and given the bizarre Social Darwinist "feuding fiefdoms" character of Nazi administration it would not surprise me in the least if the Luftwaffe tried to hog most of the production for its flak batteries (one might compare how the IJN literally hoarded all of Japan's welding gear so their Army rivals had to keep making tanks with rivets well past due date); but certainly the land army (Waffen-SS included) was already using the 75 mm caliber for a huge number of things and had the supply chains well established, so both practical logistical considerations and petty interservice rivalry bullshit (including classic "not invented here" prejudices) likely played some part.

      As an aside regarding the usefulness of armoured close support for infantry one might quote a French general (IDR which one) from the Great War who quipped something along the lines of "there are two kinds of infantry, one has never fought alongside tanks before and the other never wants to fight without them again."

    7. One might also point out that this thing was conceived and deployed specifically as a Panzerjäger, ie. dedicated tank-killer, rather than a Sturmgeschütz ie. assault gun. The traits emphasised in its chosen armament naturally reflected that intended mission envelope; SU-85 vs SU-122 might be invoked as a more pronounced illustration of the same division from across the battle line.

    8. Hmm I concur more with the Soviet counter-argument that, "if you can take something out with a single hit, why risk getting the return fire?". I'm also not sold on the advantages of having an AFV stocked with ammo; at the very least I don't see a need for any more ammo in the tank that would outlast my fuel supply (if you have to disengage to get refueled, you can get re-stocked with ammo at the same time). In the Sherman (heaps of ammo) a move was actually done to reduce the rounds it carried to something more reasonable. The advantage of having lots of ammo on hand only really applies to HE and/or smoke rounds, shot against non-armored targets that can't reply back with the same degree of effectivness; with AT ordinance in WWII tank combat at most ranges you're either very quick on the draw or very dead soon. A tank battle is over, won or lost, before you go through all those AP rounds.

      As for the SU-85 vs SU-122 comparison; I think that's somewhat true, but recall the SU-122 was pulled from service when the SU-85 was introduced. That's a shame, because I think the SU-122 had a role and indeed even for anti-tank purposes, at least fighting defensively if my life depended on it (and it would!) I'd trust my life to a hit from the ML-30 122 mm howitzer against something like a Panther's frontal armor taking it out as opposed to the 85 mm.

    9. I really don't think it makes much practical difference to the target whether the shell that comes though the armour is 75 or 88 mm you know. Real AFVs don't have hitpoints and any penetration tended to be the cue for the surviving crew to bail. For effectively identical penetration ability the better accuracy and higher RoF would seem to be more useful for the purposes of "doing unto others before they do unto you".
      Likewise I doubt the difference in explosive/frag effect is so great as to particularly matter while, say, suppressing AT guns or infantry - not that the bigger bang wasn't self-evidently desirable if you could afford it (in terms of mass and volume) ofc, but it's hardly the priority for what's primarily a tank-killer design.

      And for extended operations spare fuel is rather easier and safer to carry as external stores than ammo, just sayin'. Especially given the ever-increasing "jabo" harassement - the last thing you want is an otherwise relatively harmless strafing run setting off unprotected shells after all. And the German ability to keep the frontline properly supplied was steadily degrading throughout the later years so there certainly was a practical argument for greater built-in "campaign endurance" esp. as fuel could be to some degree salvaged from the enemy. (Hell they seriously considered trying to get turbine engines fitted in their tanks mostly because those can burn just about any kind of fuel which is valuable when you're increasingly reduced to relying on captured and scavenged supplies...)

      IDK what you mean about the SU-122, it remained in production until mid '44? SU-85 production stopped soon after as well since the much better SU-100 was nearing production status.

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