The Australian Sentinel

Nations with no prior tank building experience first began building tanks in WWII, including several nations from the British Commonwealth. Most frequently, these nations built copies of British designs, for instance the Canadian Valentines. However, Canada also built its own original tank (the Ram) on an American chassis. Australia developed and began production of fully original tanks named AC (Australian Cruiser) or Sentinel. These tanks did not see battle, but they remain a colourful chapter of world tank building history.

PzIV Penetration Trials

I previously posted about some dodgy quality armour the British found in PzIII tanks. Samples obtained from various tanks tended to behave in a similar fashion, but other trials showed that this performance was not exclusive to just one type of German medium tank. The performance of the PzIV's armour against the British 2-pounder was so disappointing, that the British theorized the Germans are saving all of their high quality plate for prospective heavy tanks.

"Firing trials by a 2 Pdr. gun mounted in a Mark IVA Cruiser tank have recently been carried out against a captured German PZKW IV 22 ton tank in the Middle East.

The armour basis of the German tank is:

• Turret:
• Front: 30 mm (1.181 inches)
• Side: 20 mm (.787 inches)
• Hull:
• Front superstructure: 60 mm (2.362 inches)
• Rear: 40 mm (1.57 inches)
• Side Centre plates: 40 mm (1.574 inches)
• End plates: 20 mm (.787 inches)

Quantity Over Quality

This penetration table is fairly well known. It appears in several period publications and a translated version was even sent to the USSR. Nevertheless, it gives some information as to how well the guns of the Western Allies performed against German armour.

However, there was one interesting observation made that didn't come along with this table to any other publication. Since hitting a tank at 2000 yards was very difficult, and the 2-pounder could penetrate older German tanks in the front and even newer ones from the side at nearly that distance, what was the point of having a 6-pounder at all?

PzIII Armour in British Hands

I previously shared how the PzIII did in Soviet hands. In summary, the 30 mm plate proved far too brittle under fire from a 45 mm gun, shattering into pieces from just one hit. Curiously, British trials find the exact same thing.

Under attack from 2-pounder AP shot, the first projectile chips off the edge, but the second shatters the plate and causes severe cracks. When the remaining pieces are tested, they too crack into pieces after one or two shots with APC shells at 20 and 30 degrees. The British had more than just one hatch, however, and also observed the welding seams coming apart after the shots. The velocities matched those for 1200 yards in the test with AP and 1000 yards with APC. 

However, things get even more interesting after. In trials against a later model PzIII, one with 50 mm of front armour, the 2-pounder can get a shot through the front plate from 100 yards, although the projectile shatters. Interestingly enough, in Soviet trials, the 2-pounder only managed to penetrate the upper edge of the StuG's upper plate (also 50 mm thick) once from 100 meters. The testers were unable to reproduce this penetration from 50 or 100 meters. The Soviet conclusion is that the 2-pounder cannot penetrate 50 mm of armour at any distance, whereas the British are content with its ability to penetrate the German tank from 100 yards. The British also establish that the 2-pounder can defeat a PzIII from the front from 300 yards with HV ammo, but the Soviets didn't have any available.

StuG in the USSR

At the start of the Great Patriotic War, Soviet military intelligence and the GAU had a very approximate idea about the types and characteristics of German tanks. This deficiency led to an overestimation of the possibilities of German armour and the launch of the KV-3, 4, and 5 programs in March of 1941. Even information on real German tanks was sparse. Intelligence missed the increase of the front armour of PzIII and PzIV tanks to 50 mm and use of 50 mm guns. This lack of information had to be made up for in the most reliable way during the war: studying trophies. Among the vehicles that were glossed over by Soviet intelligence was the StuG assault gun.

Present from Kiev

The first use of this vehicle, envisioned by Field Marshall Manstein, was in France, in May-June of 1940. It would be incorrect so say that Soviet intelligence learned nothing about the StuG. However, it did not earn much attention, and its description was brief.

"As a rule, assault gun squadrons accompany infantry in attacks of fortified positions and strongholds in the direction of the main attack, first in motorized divisions, then later in tank and infantry divisions. The squadrons are armed with 75 mm tank guns installed on the chassis of the PzIII medium tank with a special turret and armour. The main task for these vehicles is the destruction of the enemy with direct fire."

The Soviet military had no idea about the importance and effectiveness of these low, mobile, and well armed fighting machines. Meanwhile, in June of 1941, more than 10 StuG battalions (Sturmgeschütz-Abteilung, or StuG.Abt.) assembled on the Soviet border. Among them was 197th StuG. Abt. under the command of Major Helmuth Christ.

Red Armymen posing on a captured StuG III from StuG. Abt. 197, August 1941.

This battalion was formed in October of 1940 and was armed with StuG Ausf. B vehicles. StuG. Abt. 197 had its baptism by fire alongside the 132nd Infantry Division in May of 1941 during the invasion of Yugoslavia. During the start of the invasion of the USSR, the battalion was subordinate to 

XXXXVIII Tank Corps of Army Group Center. Soon after the fighting began, it was transferred to XXXXIV Corps in Army Group South.

That same vehicle at the NIIBT Proving Grounds, early September of 1941. The damage to the suspension and the letter E on the side can be clearly seen.

On August 15th, the battalion was located at the city of Kanev, where fierce battles for the Dnieper were fought. Soviet infantry counterattacks managed to capture at least two StuG III Ausf. B from StuG. Abt. 197. The vehicles from 3rd battery was captured intact and was used in a photoshoot with the soldiers who captured it. The second vehicle, #90247 with the name Prinz Eugen, was also mobile. According to StuG. Abt. 197 records, both vehicles were lost after hitting mines. After brief repairs, they were transferred to the Soviet rear.

The assertion that at least one of the vehicles went to fight with a Soviet crew is often made, but this is not true. In early September, the vehicles from 3rd battery was already at the NIIBT Proving Grounds. As for Prinz Eugen, it was transferred to the rear of the Central Front. A brief description was composed, with the trophy getting the name "medium German tank T-3 with an immobile turret". The description included external and internal characteristics of the vehicle. These characteristics were fairly close to the real ones. Despite the urgency, the specialists who studied the vehicle had time to partially take it apart and put it back together.

The second captured StuG III Ausf. B from StuG. Abt. 197.

The NIIBT Proving Grounds went in a different direction. Instead of beginning a detailed study, they made a brief composition of its characteristics. A summary of German armour was ready by September 11th, 1941. The tactical-technical characteristics in this summary were more precise, especially when it came to armour thickness. Aside from measurements, a brief trials were also staged, where the StuG reached a speed of 50 kph.

That same vehicle from the left. This StuG had the personal name "Prinz Eugen".

In NIIBT documents, the StuG was referred to as "artillery tank" or "Artsturm" for short. It's not known who invented this term, but it stuck to the StuG in Soviet documents.

Tough Nut

The StuG III was studied to compose a guidebook on German vehicles that was so desperately needed at the front. Because of this, trials were performed in an accelerated way, and some conclusions may be unfounded.

StuG III from the rear.

"The artillery assault tank is designed to act in the first echelon of tanks. The tank has no turret. It can only fire forward in a 28 degree arc by turning the gun on a mount. There are no machineguns. The lower part of the artillery tank, the suspension, the engine, the planetary turning mechanism, and the controls are taken from the PzIII. The gearbox is the same as the one on the PzII Ausf. B and only differs in its size. 

The armour of the tank can be defeated by guns of all calibers. It is possible to destroy the tank through the opening above the gun mount using a bottle of incendiary fluid or a grenade."

The conclusions regarding protection seems hasty. Of course, there were some poor decisions made regarding the vehicle, and the protection of the casemate was one of them. The gun sight opening "caught" shells, but it was changed in the Ausf. C version. The gun mount was also far from ideal as far as shell resistance went. However, the protection offered by the front armour went underappreciated by the proving grounds. The StuG III was the first mass produced German vehicle with anti-shell armour. The front armour of even the StuG III Ausf. A was 50 mm. The vehicle was reliably protected from the 37 mm gun. The PzIII and PzIV only received improved armour a year later.

Poster with vulnerable parts of the StuG, which slightly differed in reality.

It was already obvious that the 45 mm gun will have problems with German armour in late 1940. A 30 mm thick evacuation hatch from a PzIII tank bought in Germany was fired upon, penetrated, and even shattered, but not on the first try. These results showed that thicker armour would be impenetrable. Nevertheless, in September of 1941, the verdict was "vulnerable to artillery of all calibers". The same verdict was repeated in the flyer from the "Destroy German Tanks" series.

A full fledged study of the vehicle's armour was only made in September of 1942. PzIII, PzIV, Pz38(t) and the StuG were tested at the NIIBT Proving Grounds at Kubinka and their Kazan branch. The tanks were fired upon by Soviet, American, British, German, Czechoslovak, and French tank guns. Their resistance at 50, 100, 200, 400, 600, and 800 meters was measured.

Results of firing the 45 mm gun (1 and 2).

First, the vehicle was fired upon by the 45 mm mod. 1942 tank gun in the T-70 tank. It penetrated the 30 mm armour with no problems from a range of 850 meters. Firing at the front was a different story. From 100, then 50 meters, the result was the same: 20 mm dent. The shells fell apart on impact.

Hits from 2-pdr shells. The penetration was likely by chance.

The story can end here with the conclusion that Soviet armament was bad, but similar results were shown by another gun: the British 2-pdr (40 mm) in a Canadian Valentine VII tank. The sides also proved effortless. As for the front armour, it was only penetrated once, and the penetration was deemed unsatisfactory, since the shell landed into the joint between the central and lower front plates. In all other cases, the shells made 25 mm deep dents. One can only feel sorry for British tankers whose main armament was the 2-pdr gun until the fall of 1942.

Penetrations by 37 mm subcaliber rounds from the A-7 gun on the Pz38(t)

A similar result was attained by the 37 mm A-7 gun on the Czechoslovak Pz38(t) tank. It could confidently penetrate the sides, but the front was invulnerable: the shells left 40 mm deep dents. The results were different for subcaliber shells: they could penetrate at 100, 200, and 400 meters.

The 37 mm M5 gun installed in the American light M3 tank performed better. Its M51 shell easily penetrated the front of the StuG at 100 meters, and 35-50 mm deep dents were formed at 150 meters. This can primarily be explained by the larger casing size used by Gladeon Barnes in its creation, giving the gun's shells a higher velocity compared to British and Soviet analogues.

The ordinary armour piercing shell from the M5 37 mm gun confidently penetrates the front armour.

The 47 mm SA 35 gun on the Somua S35 was even more effective. It could penetrate the front of the StuG III from 400 meters, but at this range only every other shot penetrated. The German 5 cm KwK 38 L/42, the stock armament on PzIII tanks by 1942, could penetrate the front of the StuG at 800 meters.

Penetrations left by the SA 35 gun installed in the French Somua S35 tank.

The 75 mm M2 gun used in the American M3 medium tank achieved curious results. The first Lend-Lease convoys didn't bring armour piercing ammunition, so HE was used. The results were poor, not a single penetration was made. The maximum that was achieved was a 10 mm dent. In addition, a deep dent was formed in the transmission cover while firing at the upper front plate. The 76 mm F-34 achieved different results and made Swiss cheese from the StuG at all distances. The armour caved in upon impact, forming many fragments.

Results of the 75 mm M2 gun used on the American M3 medium tank.

Landmark

At the same time, the StuG III was being studied at NII-48. The composition of the armour and joints between plates were being examined and successful design decisions that could be implemented in Soviet production were extracted. 

"The hull of the German Artsturm tank:

The hull is welded. The ceiling of the fighting compartment is attached by bolts with a hidden head. Initially, the front plate was 50 mm thick, the sides were 30 mm thick, and the rear was 20 mm thick. Later, the rear 20 mm plates were replaced by 50 mm plates.

The hull is composed of rolled Chromium steel with 0.1% Vanadium. The Brinell hardness of the plates is 337-476, the diameter of the print is 2.8-3.32. The armour is malleable, has good resistance, and doesn't chip.

...

German PzIII, PzIV, and Artsturm tanks are made with Chromium steel and have good shell resistance. The composition of armour can be used to produce armour thicker than 50 mm. Curing, rolling, thermal conditioning and welding of Chromium steels mark 5140 and 5150 is already mastered by our industry and putting this armour into production will not be a problem.

A Chromium electrode containing 2.1% Chrome and 0.2% Carbon can be recommender."

Layout of the StuG's armour from NII-48's report.

It is worth mentioning that work on 45 mm subcaliber shells and a 45 mm gun with a lengthened barrel was going on before the trials of German tanks. The results of the trials only hurried both designs.

Initially, the German novelty was of no interest to Soviet designers. Later, the StuG III had a big effect on the development of medium self propelled artillery. Before, Soviet SPG designs were, as a rule, open topped tank destroyers with rotating turrets, like the U-20 project. By spring of 1942, the priorities shifted to assault guns with closed casemates, similar to the StuG III, but that is a topic for another article.

Original article by Yuri Pasholok.

Valentine Mods in the USSR

The Infantry Tank Mk.III, or Valentine, was the most produced British tank of WWII. However, the British themselves actively used Valentines from 1941 to the first half of 1943. The Soviet Union, who received almost half of these tanks, used them much more actively. Known as "Valentin" or MK-3/MK-III, these tanks debuted in the Battle for Moscow in the fall of 1941 and survived until the end of the war in some units. The Valentine was one of a few foreign tanks that saw a large scale conversion effort.

Swap the Gun

In the summer of 1941, when the issue of shipping tanks to the USSR was first explored, the Soviet side scrupulously studied them. Cruiser tanks were rejected outright. Among light tanks, only 20 Tetrarchs were ordered. Mainly, the Valentine and Matilda were chosen. The slow speed was compensated by thick armour for their class and a diesel engine, which was an especially important feature for the Soviet purchasing commission. It is worth mentioning that these sales had nothing to do with the Lend-Lease program. The tank were not rented, but paid for in full, partially with gold.

The first Valentine tanks arrived in the USSR on October 11th, 1941. During their use, many defects were discovered. According to "memorandum on the issue of English Mk-III* tanks" dated November 20th, 1941, track pins broke very easily. Trials showed that the track pins broke due to excessive tightening of the tracks performed by British instructors. In the winter, it was discovered that the tracks had to be equipped with spurs, as the tracks were packed full of compressed snow and ice and lost traction. There were many instances of the tires slipping off the wheels. The tank was poorly protected from incendiary fluid, as there were openings in the turret roof and gun mantlet. The protection of the engine compartment was similarly poor.

The main problem was with armament. British tank doctrine excluded HE-fragmentation shells from the ammo racks of vehicles using 2-pdr guns. According to tank theorists, machineguns were enough to fight off infantry. The gun was meant for fighting tanks. There were also no APHE shells; the gun fired solid AP shot. This fact caused confusion among the Soviets. According to intelligence information, the shells existed, and even a sketch was provided. In reality, no such shells existed. The Valentine also had 50 mm grenade launchers which were only equipped with smoke rounds, even though the British had a 50 mm infantry mortar with HE-fragmentation rounds.

"40 mm APHE-T shell. We did not receive these. The shell's mass is 1038 g."

The shells that, according to intelligence reports, the British had, but did not send.

The ammunition nomenclature was far from the only problem. Tanks that came with the first convoys weren't fully equipped. Bren machineguns and Thompson submachineguns were missing. There were several cases of tanks arriving with no guns. In addition, there were no spare barrels, and only 5-6 loads of ammunition per tank, which was very little. The situation was very grim: as soon as the tank's barrel was damaged or ammunition consumed, it became a tankette.

GABTU considered the installation of the Soviet 45 mm gun as the best option. This work was assigned to Major-General V.G. Grabin's factory #92 in November of 1941. P.F. Muravyev was put in charge of the project. A Valentine II with registration number 27526 was selected for conversion.

A Valentine II with a 45 mm gun, December 1941.

According to the report, only the main gun and BESA machinegun were removed, replaced with the Soviet 45 mm gun and DT machinegun, solving the ammo shortage for both weapons. The 50 mm grenade launchers remained. Factory #92 designed new armour for the front of the turret and gun mantlet, far better than the British originals. The shorter brass catcher and other conversions allowed increasing space inside the turret, which the Valentine didn't have an excess of. The tank's ammunition capacity also grew from 59 2-pdr shells to 91 45 mm shells. The gun was indexed F-95.

The freed up main gun would be sent to repair bases and the machinegun would be given to infantry. The greatest benefit was the use of a domestic gun and sights, removing the dependence on foreign delivery. The sorely lacking HE shell was also introduced into the tank's repertoire.

The same tank, front view. Unlike the stock mantlet, this design could not be jammed by enemy shells.

Trials showed that the re-armed Valentine was no harder to load than the stock variant. The gunner's working conditions also did not suffer. A trial run over a 20 km track did not reveal any defects in the gun or sight. After successful factory trials, the tank was sent to Moscow and presented to members of the government.

45 mm F-95 gun and coaxial DT machinegun.

A proposal to build a batch of these guns was raised even before the trials were completed. However, the very successful program was suddenly shut down by GABTU. One of the reasons for this unpredictable end can be found in a report by GABTU chief, Lieutenant-General Fedorenko, to L.P. Beriya on January 9th, 1942.

"Chief Designer of factory #92, Major-General of the Technical Forces comrade Grabin, installed domestic armament into two English tanks, the Matilda and Valentine.

In the Valentine, our 45 mm gun and the DT machinegun are used instead of the English 40 mm gun and 7.92 mm machinegun. Experimental prototypes were tested at factory #92 in Gorkiy and then sent to Moscow.

Based on personal observations and trials of the materials, I conclude that the re-armament of English tanks should not proceed for the following reasons:

1. Valentine tank. The 45 mm gun has almost identical penetration compared to the 40 mm gun, and it is reasonable to leave the armament in place, saving our guns for domestic vehicles.

..."

In reality, there were several reasons for why the re-armament process was stopped. One of them is cooperation from the British side, which quickly reacted to GABTU's complaints. The archives preserved correspondence between representatives of GABTU and the British military mission in the USSR, headed by General Frank Noel Mason-MacFarlane (referred to as Macfarlan in the letters) in 1941-1942. This correspondence had results. Starting in December of 1941, tanks shipped to the USSR were filled with antifreeze, which drastically reduced the amount of defective engines. Lubricant suitable for use in winter was also introduced. Changes were made to the batteries and oils for recoil mechanisms. Starting in December, the amount of ammunition shipped with each tank increased to 520 rounds.

Another important reason was that there was no one free to re-arm the tanks, and there was nothing to re-arm them with. In the winter of 1941-1942, tank guns were in deficit and repair bases were overloaded with existing work.

New front turret plate.

This doesn't end the story of modified Valentines. Increasing the amount of ammunition that was shipped with the tanks didn't solve the issue of HE shells. In 1942, there was an attempt to combine the propellant and casing with a 40 mm Bofors AA gun shell. Trials were carried out, but the idea didn't reach production.

At about the same time, halfway around the world, the Australians were solving the same problem. They had greater success and mass production began in January of 1943, which were used in Matildas and Valentines until the end of the war. The British only got around to making HE shells for the 2-pounder in 1944.

Light Tanks with Heavy Armour

If the re-armament of the tank was mostly an experimental affair, then the improvement of protection was widespread. The only surviving tank in Russia, displayed at Patriot Park, is one of such vehicles. Additional 30 mm plates are welded to the front of the hull and splash protection plates are placed around the turret.

There is a theory that this is no more than an experiment, but that is not so. For instance, the tank saw combat. It arrived in the USSR on December 12th, 1941, and was included in the 171st Independent Tank Battalion fighting on the Kalinin Front on December 16th. The extra armour and front of the turret have marks from bullet impacts. It's doubtful that the Kubinka proving grounds, where the tank arrived in 1945, would perform such trials. Additionally, and perhaps most importantly, a photo exists with several of these tanks with identical front armour and a ring around the turret, dated 1943.

Valentine II with additional armour, registration number T.27543, Patriot Park.

Official GABTU correspondence doesn't have a single line about applique armour. Work on improving the Valentine's protection was done unofficially, most likely within a single unit. The improved armour was directly connected with the introduction of long 75 mm guns in both towed (Pak 40) and mounted (KwK 40/StuK 40) variants in the spring of 1942. For this gun, 60 mm was not much of a challenge, and the Valentine lost one of its main advantages. An extra 30 mm of armour drastically improved the chances of nonpenetration if the shell struck the front of the tank.

Tanks with the same armour as the Valentine II in Kubinka. The photo is labelled as being taken on the Western Front in 1942, but judging by the tankers' shoulderboards, it was taken no earlier than 1943.

As the extra armour was improvised, there was no systematic approach. Each unit performed their upgrade individually. Usually, the applique armour was added to the front plates, and the thickness could vary based on available armour. The ring around the turret, like on the Patriot Park tank, was a rare occurrence. Both early and later models were equipped with additional armour. With this addition, Valentine Mk.IX tanks armed with a 6-pounder (57 mm) gun approached the KV tank in terms of armament and armour. The mass of the armour was relatively small and did not impact the characteristics of the tank.

Valentine with additional armour in Vilnius, 1944. There is no splash guard around the turret ring. Judging by the impact mark, the tank benefited from this extra armour at least once.

The only place where any information about this phenomenon exists is the GABTU Department of Inventions archive. On November 10th, 1942, a letter arrived from technical assistant to the commmander of the 167th Tank Brigade, Engineer-Major A.G. Aranovich. The gist of his proposal can be inferred from the title: "Applique armour for the MK-3"

"Combat experience from the tank brigade on the South-Western, Stalingrad, and Don Fronts shows that the MK-3 needs applique armour in the following places:

1. The upper front plate can be penetrated by a 75 mm gun from all distances due to its vertical placement and is too thin. The extra armour should be installed on a slope (see blueprint).
2. The lower front plate must also be reinforced, with the extra armour being placed on an angle (see blueprint).
3. The weakest place is the turret ring, where the armour is weakened by connections with the side plates and the rotation mechanism. Evacuated tanks from the battlefield show that enemy gunners aim for this point first in order to jam the turret, and always penetrates due to the tank's weakness. It is necessary to protect the turret ring with armour plates and rubber liner so that the trajectory of the shell changes on impact and penetrations are prevented."

Aleksandr Grigoryevich knew what he was talking about. He personally recovered three Valentines and one T-70 from the battlefield. The vehicles were repaired within a day and were sent into battle. For this act, Engineer-Major Aranovich was awarded the Order of the Red Star.

"Sketch of the front part of the Mk-III. Armour thickness: 45 mm"

Applique armour for the front of the Valentine tank, developed by Engineer-Major Aranovich.

This method was the thickest and best designed among all proposed. not only was the resulting armour 105 mm thick, but it was placed at an angle, increasing the effectiveness. The protection of the turret ring is also a well thought out idea. However, GABTU declined the idea, making the brief excuse that it is not desirable to increase the tank's mass.

"Sketch of the Mk-III turret (the turret ring is protected).

Protection of the turret ring from being jammed by shells.

This could be the end, since the materials ended up in the Department of Inventions archive, but in his accompanying memo, Engineer-Major Aranovich says that his unit managed to install this armour on three tanks, perhaps the three tanks that he personally pulled from the battlefield. The memo says that the vehicles went into battle multiple times, and the extra armour was indeed effective.

In the summer of 1943, Engineer-Major Aranovich distinguished himself at Ponyri. For skilled actions during evacuation and repairs of tanks, he received the Order of the Patriotic War 2nd Class. He finished the war with the rank of Lieutenant-Colonel.

Spurs for the Valentine

Although less so than the Matilda, the Valentine still suffered from problems with traction. This problem was most prevalent during the winter, which was confirmed by trials of a Valentine II at Kubinka.

"Trials of the tank in winter conditions showed that the shape of the track links does not provide traction with the ground, as a result of which the performance of the tank is insufficient in winter."

The solution was discovered during the trials. Engineers from the attached research institute developed two types of spurs that were produced and tested. The first type involved welding on 35 mm long grousers. The second type was better designed and allowed removal when necessary. It was held in place by the stock track pin. According to results of the trials, both types of spurs were deemed reliable. Seemingly, both were sent into the army.

Two types of spurs developed in the winter of 1942.

Work on spurs did not end here. In November of 1943, a certain Zakharenkov proposed permanent spurs produced from "angled iron made into a wavy shape" and welded onto the track. Having studied the proposal, the proving grounds concluded that it did not make sense to produce this design. It was difficult to produce in the field and the nature of the spurs made them impossible to remove when driving on good quality roads.

In May of 1943, a group at the proving grounds research institute consisting of Technician-Lieutenant A.S. Lobakov, Engineer-Major A.M. Zenin and Engineer-Captain I.A. Kondrashev designed an improved type of removable spurs. The biggest change was in the shape of the grouser, which made driving on snow easier. Trials showed that this design radically improved performance on snow.

Improved spurs for the Valentine.

According to the instructions developed by the proving grounds research institute, each track had 8 spurs (with 12-13 track links between them). These spurs were produced in repair workshops. For the development of a well designed and simple spur, Marshall Fedorenko declared his gratitude and awarded 1000 roubles to each member of the group. A patent was filed on March 5th, 1944.

For Production

In conclusion, let me tell you about another vehicle that was far from unique. Sadly, aside from mentions in text, no information is available.

In the summer of 1944, repair factory #12 in Baku, mostly tasked with repairs of British and American vehicles, was moved to Saratov. In addition to foreign tanks, 12 (later 10) T-26 tanks and one BA-10 armoured car were present at the factory in the summer of 1944. Two T-26es were converted to tractors to be used at the factory.

This report is the first mention of a Valentine tractor.

Another item interests us. This report of vehicles present in August of 1944 lists a tractor on the MK-III chassis. The report states that it was used by the factory. There were no mentions of any more such conversions at factory #12, but factory #82 (Moscow) mentions the construction of two tractors on the chassis of British tanks in April of 1945. 11 more vehicles were made in June and 14 in July. According to the reports, there were enough tanks to make 5 more tractors. There is also information on conversion of Valentines into tractors after the war. Abroad, the conversions of Valentine tanks into turretless training vehicles or even mobile water tanks were rather common.

Original article by Yuri Pasholok.

2-pounder HE

Many lamentations have been recorded about the lack of explosive shells for British 2-pounder guns. One solution I've seen involved jury-rigging smoke launchers to fire mortar shells. Another is a little more reasonable.

"A program of trials of 40 mm English high explosive fragmentation tracer AA shells in tank guns

1. Goal of trials: to establish the possibility of using 40 mm AA shells in a tank gun. Before trials, the following work is done:
1. The 40 mm shell is disassembled.
2. The possibility of firmly loading an AA high explosive fragmentation shell into a tank shell casing is tested. The firmness of the load is tested by loading the shell into a tank gun.
3. The tank gun rifling and shell driving band are measured in order to discover the necessary forcing of the band for satisfactory loading of the shell (not having the driving band prematurely stick into the rifling).
4. The maximum pressure the shell can bear is calculated by examining mechanical characteristics of the shell and its size.
2. Supplies for trials:
1. System: 40 mm English tank gun.
2. Shell: 40 mm English AA high explosive shell.
3. Casing: from the 40 mm tank gun.
4. Propellant: propellant from the English AA shell and domestic propellant with ballistic characteristics close to English 40 mm shell propellant.
3. Trial process:
1. Discovery of the propellant load to achieve V0=790 m/s and pressure less than the maximum acceptable pressure calculated in point 4.
   Note: according to information possessed by Artkom, the maximum acceptable pressure for the 40 mm AA high explosive fragmentation tracer shell is 3000 kg/cm^2. This information needs to be confirmed.
2. Discovery of the propellant load to achieve V0=790 m/s using domestic propellant following points 1 and 3. Propellant will be tested on inert shells. If it is not possible to disarm the shells, testing will be done on shells that are incompletely armed with an inert detonator.
   If it is not possible to achieve a velocity of 790 m/s without surpassing acceptable pressure, trials will continue with the maximum velocity attainable at this pressure.
3. Further trials will be carried out according to typical testing procedure applicable to HE shells (aside from point 1), using the propellant load established in these trials. Increased pressure is considered 1.1 times the current working pressure.

The trial report should include data for the formation of ballistic tables. The report should also include English markings on the 40 mm shells."

CAMD RF 38-11355-692

Accuracy Revisited

A while ago, I wrote an article comparing the accuracy of a few guns: the D-25, 88L/56, 88L/71, and ML-20. That article lacked a few details, which I will explain here.

The article talked about how the Germans calculated gun accuracy: using a percentage figure for how often you can expect to hit a 2 meter by 2.5 meter target at a certain distance. Such a measurement is useful for when you are fighting a tank that is 2 meters tall and 2.5 meters wide, and not really in any other case.

The Soviet measurement of accuracy is deviation. You will see many deviations in test documents, but the most important figure, the one that actually makes it into artillery tables and textbooks, is the expected deviation. The average deviation comes in 3 components: vertical, horizontal, and distance. For direct fire, vertical and horizontal are important, for indirect fire, distance and horizontal.

Expected deviation is similar to the 50% radius, except in only one direction. 50% of the shells will land on the closer side of the expected deviation figure, 50% of the shells will land on the further side. Using the two expected deviation figures, you can create an oval inside of which 50% of your shells will go.

Let's revisit the guns in the previous accuracy article. The D-25 has a 50% radius of 24 cm. However, you can see that the distribution of shots in that radius is not circular, it is an oval. I don't have the exact data for the D-25's average deviations, but you can clearly see that the result would be an oval that is a little shorter than it is wide. It is pretty trivial to deduce that the value of the deviations should be approximately 24 cm.

A non-circular result is very common. The ML-20 in that same article has a 50% radius of 32 cm at 1000 meters. However, the average deviations are different from that: 22 cm for vertical and 33 cm for horizontal.

Now, on to some new guns! Artillery tables contain expected deviations for lots of distances and propellant charges, but I will obviously not list all of them. The deviations will be given for 1000 meters, at a full charge, with as many shells as I have tables for. Deviations are taken from the appropriate Soviet artillery table. I have the full ones, so if you need them, ask. For each gun, I will also give the distance at which it can hit a German target 50% of the time with the regular AP shell, to compare it with the German accuracy metric.

Let's start with a classic, the 76 mm F-34 gun, mounted on the T-34-76 models 1941 and 1942:

• HE shell OF-350, O-350A, and D-350 smoke grenade:
• Vertical: 30 cm
• Horizontal: 30 cm
• Trend: horizontal deviation grows much slower than vertical deviation.
• AP shell Br-350A and Br-350B
• Vertical: 30 cm
• Horizontal: 30 cm
• Trend: horizontal deviation grows a little slower than vertical deviation.
• HEAT shell UBP-353A
• Vertical: 50 cm
• Horizontal: 50 cm
• Trend: deviations grow at the same rate.

Looking at a very extreme range, the F-34 has an average deviation of only 1 meter at 3 km. That means that the German 2x2.5 meter target would still be hit more than half the time. Jentz writes that the Tiger could hit the target 53% of the time at that range. Pretty comparable.

The 122 mm model 1938 howitzer (M-30) has the following deviations:

• HE shells OF-462 and O-462A, smoke shell D-462
• Vertical: 50 cm
• Horizontal: 60 cm
• Trend: vertical deviation grows a little faster than horizontal deviation.

The range at which the gun can hit the above German target 50% of the time is 2000 meters. 

The 45 mm model 1942 gun isn't quite that accurate (model 1932 and 1937 results are identical):

• AP shell Br-240 and shrapnel O-240 and O-240A
• Vertical: 50 cm
• Horizontal: 60 cm
• Trend: horizontal deviation grows faster than vertical.
• APCR shell Br-240P
• Vertical: 50 cm
• Horizontal: 50 cm
• Trend: horizontal and vertical deviations grow at the same rate.

The deviation gets to around 1 meter in each direction at 2000 meters, not that there is much a 45 mm gun can penetrate at that range. 

Here is a gun we haven't seen before: the T-60's ShVAK 20 mm autocannon:

• AP incendiary and fragmentation-incendiary shells:
• Vertical: 70 cm
• Horizontal: 70 cm
• Trend: vertical deviation grows faster than horizontal deviation.

The distance at which a German target has a 50% hit ratio is 1500 meters.

The 12.7 mm DShK was in a T-40 tank, that's tank gun enough for me!

• B-32 AP bullet
• Vertical: 76 cm
• Horizontal: 59 cm
• Trend: vertical grows faster than horizontal.
• BZT-44 AP-incendiary bullet
• Vertical: 98 cm
• Horizontal: 67 cm
• Trend: vertical grows faster than horizontal.

The 50% distance is also 1500 meters.

That's all I have for now on the Soviets, so now let's take a look at some foreign guns. The first up is the British 40 mm 2-pounder.

• AP shell and AP shot
• Vertical: 40 cm
• Horizontal: 20 cm
• Trend: horizontal deviation grows much faster than vertical deviation, despite starting out smaller.

This gun hits the German target 50% of the time at a distance of about 2250 meters.

Now, some American guns. First, the 75 mm M2, from the M3 Lee.

• AP shells M61 and M72
• Vertical: 30 cm
• Horizontal: 30 cm
• Trend: vertical deviation grows much faster than horizontal deviation.
• HE shells M48 and MK1
• Vertical: 40 cm
• Horizontal: 30 cm
• Trend: vertical deviation grows much faster than horizontal deviation.

The range at which this gun hits a German target 50% of the time is about 2250 meters.

The other gun on the M3 Lee, the 37 mm M5:

• AP shell M51
• Vertical: 40 cm
• Horizontal: 40 cm
• Trend: vertical and horizontal deviations grow at the same rate.

The range at which this gun hits a German target 50% of the time is a bit less than 2000 meters.

Next, the German guns. The 3.7 cm PaK gives the following results:

• AP Pzgr
• Vertical: 50 cm
• Horizontal: 50 cm
• Trend: vertical and horizontal deviations grow at the same rate.
• HE Spgr
• Vertical: 50 cm
• Horizontal: 30 cm
• Trend: vertical grows much faster than horizontal.

The gun loses enough penetration to not be of any use before it can fail to hit a 2*2.5 meter target 50% of the time, (the table only goes up to 1500 meters). 

The German heavy 105 mm model 1918 gun has the following deviations:

• HE 19 KPS and FES (deviation given in meters)
• Vertical: less than a meter
• Horizontal: less than a meter
• Trend: vertical deviation grows faster than horizontal deviation.
• AP Pzgr. rot.
• Vertical: 40 cm
• Horizontal: 20 cm
• Trend: vertical deviation grows much faster than horizontal deviation.

Due to the rapidly growing vertical deviation, it is not possible to accurately gauge the 50% distance. It would be somewhere just over 2000 meters.

In conclusion: the average deviation for most guns is more or less in the same range, 30-50 cm at 1000 meters. Even with the largest deviation (98 cm on the the worst machine gun bullet), a gun is going to hit any remotely tank-sized object more than half the time. Penetration is the issue here, as a lot of these guns can shoot much further than they can usefully penetrate anything.

The myth of superior German accuracy is, once again, proven false. The average deviation of the D-25 is comparable to the 88L/71, and the long-range accuracy of the F-34 is the same as the 88L/56.

Update: I found the complete artillery table for the 88L/71 KwK 43 gun. It is posted here. 

British Guns vs German Tanks

Since large amounts of British and American Lend-Lease vehicles were shipped to the Soviet Union, it was important to know how well they perform against German tanks. The 1942 "Report on the shooting of German tanks with AP and HE shells from tank guns" (CAMD RF 38-11355-832) tests the 40 mm QF 2-pounder gun on the Valentine MkIII.

First up for the test was the Czech LT vz 38, used by the German Wehrmacht under the designation PzKpfw 38(t).

At 250 meters, the 2-pounder penetrates the first 25 mm plate of the front armour, but does not penetrate the second. The front plate develops a crack 250 mm long. At 400 meters, it can only form a 7 mm deep dent in the first armour plate. Closing in to 200 meters, the Valentine fires at the front plate of the turret platform and penetrates. A hole is formed, 50 mm in radius. Cracks run though the first armour plate, 200 mm around the breach. 5 bolts holding the front armour plate in place are torn off. Firing again, from 600 meters, the shot forms a crack from the top to the bottom of the front armour plate. 

Moving on to the side, the first shot penetrates the turret all the way through. One hole on the left side, 55 mm entrance diameter, 70 mm exit diameter. One hole on the right side, 38 mm entrance and 38 mm exit diameter. Another shot at 600 penetrates the turret, and also the ammunition rack of the tank. 

At 800 meters, the Valentine penetrates the side of the turret, forming two cracks, 600 and 400 mm long. 10 bolts holding the armour plate on are torn off. Another shot from 800 meters penetrates the side of the turret platform, forming two 300 mm cracks, and causing spalling. 

Moving to the front of the tank again, the Valentine fires a shot at the upper sloped plate at 400 meters. A section of the armour, 300 mm by 140 mm, is broken off. Another shot at the lower sloped plate breaks off a piece 100 mm by 150 mm and penetrates the gas tank.

Conclusions: "The 40 mm AP shell does not penetrate front armour 50 (25+25) mm thick. The reason for this is poor quality of the shells. They are destroyed completely on impact.

The 30 mm side armour can be penetrated from 800-1000 meters."

That's it for the vz 38. The armour plates are overly hardened, as we've seen on the Tiger II. This causes the plates to crack, spall, and fall off. Still, the front 50 mm of armour prove to be a challenging opponent for the 2-pounder at any distance. 

Next up for testing is the StuG III. At 50 meters, the 2-pounder only forms a 20 mm deep dent in the StuG's front armour. However, at 100 meters, it manages to penetrate the upper part of the front plate. That result does not repeat, as another shot from 100 meters only makes a 25 mm deep dent. 4 shots from the side, all at 850 meters, go through.

Conclusion: "The 40 mm tank gun penetrates the side of the hull, 30 mm thick, from 850 meters. The front of the hull, 50 mm thick, is not reliably penetrable at any distance due to the poor shell quality. Upon impact, the shells shatter into small fragments."

The Valentine gets another turn, this time against a PzIII. The results are similar to the StuG. It cannot penetrate the front at 100, or even 50, meters. 

In the conclusions, the following is noted: "The British 40 mm shell, when fired at a 50 mm armour plate from 50-100 meters, makes a 20-25 mm dent and shatters. " ... "Scattering of shells from the 37 mm and 40 mm guns does not exceed the size of a StuG at 800 meters."

Quite a poor showing by the country that invented tanks in the first place! Let's see how their larger gun fares. Another test pits the 6-pounder from the Churchill MkIV against the Tiger.

"Target: turret. Armour thickness: 82 mm. Distance: 800 m. Result: penetration. Entrance hole 82 mm in diameter, exit hole, 75 mm in diameter

Target: turret. Armour thickness: 82 mm. Distance: 1000 m. Result: dent 90 mm deep, 90 mm in diameter. Inside, a 10 mm bump is formed, with a crack.

CAMD RF 38-11377-12

Target: turret. Armour thickness: 82 mm. Distance: 1000 m. Result: dent 120 mm by 80 mm, 70 mm deep. Bump on the inside.

Target: side. Armour thickness: 82 mm. Distance: 1000 m. Result: penetration, entrance hole 70 mm in diameter, exit hole 115 mm in diameter.

CAMD RF 38-11377-12

Target: side. Armour thickness: 82 mm. Distance: 625 meters. Result: penetration, breach diameter 58 mm.

Target: side. Armour thickness: 82 mm. Distance: 625 meters. Result: unsatisfactory hit on the bottom of the armour plate."

There's a comeback! Gone is the poor shell quality of the 2-pounder. Instead of shattering into dust on impact, the 6-pounder penetrates German armour at a great distance. The armour, on the other hand, is worse than what we saw on the StuG, with cracking and large diameter holes.