Video: When is the T-34 a Tank Destroyer?

A new video is up! This is a second video on my series on Soviet tank destroyers. This time I take a look at what exactly defines a tank destroyer and dispel some myths about the elusive T-34 tank armed with the 57 mm ZIS-4 gun.

You'll be pleased to know that I bought a new microphone and the quality of the audio increased dramatically since my previous recordings.

 

Pre-War Potential

As worldwide tank building practice shows, it takes about five years to develop a new tank in peace time from the development of the requirements to the final product. The tank often changes significantly between envisioning and production, as happened with the T-34. The initial requirements for the BT-20 tank composed in mid-October of 1937 described a convertible drive tank weighing 13-14 tons with 20-25 mm of armour and armed with a 45 mm gun or 76 mm L-10 gun. Three years later, the tank that went into production was fully tracked, weighed 25.6 tons, had an L-11 gun and 45 mm thick armour.

The mass grew gradually during development along with the improvement of the tank's characteristics. However, the T-34 was supposed to change significantly by the summer of 1941. This T-34M was the result of changing requirements. The start of the Great Patriotic War got in the way of developing even a prototype, but the T-34M became the starting point for a whole series of tanks and had an effect on the production T-34.

"T-34-57"

Out of the many resilient myths that surround the T-34 tank, there are several that revolve around the rarest one of them all: the T-34 tank armed with the 57 mm ZIS-4 gun, specifically the four experimental tanks produced in 1943. Many sources give these tanks and their guns some kind of made up name like T-34-57 or ZIS-4M and claim that these tanks fought in "special tank company #100" from August 15th, 1943. All three of those claims are false.

ZIS-5, Take One

"May 30th, 1941
To the Central Committee of the VKP(b)
Comrade Zhdanov

According to USSR SNK and Central Committee Decree #1216-502 issued on May 5th, 1941, two experimental T-44 tanks built by factory #183 are supporsed to be armed with the 76 mm ZIS-5 or 57 mm ZIS-4 gun. The main characteristics of these guns is shown in the following table:

Gun model	Caliber in mm	Muzzle velocity, m/s	Shell mass, kg	Penetrates armour
				At 0 degrees		At 30 degrees
				Thickness in mm	Distance in m	Thickness in mm	Distance in m
F-34	76.2	662	6.3	60	Up to 1000	50	Up to 1000
ZIS-5	76.2	813	6.5	90	Up to 1000	70	Up to 1000
ZIS-4	57	992	3.14	90	Up to 1000	70	Up to 1000

New AT Guns

"State Committee of Defense Decree #3187
April 15th, 1943
Moscow, Kremlin

On measures for reinforcement of anti-tank defenses.

In order to strengthen our anti-tank defenses, the State Committee of Defense decrees that:

1. The People's Commissar of Armament, comrade Ustinov, must replace the production of 45 mm mod. 1937 guns at factory #172 with 45 mm M-42 guns, following this schedule:
1. April: 250 units
2. May: 300
3. June: 400
4. July: 600
5. August: 800
6. September: all production
2. The People's Commissar of Armament, comrade Ustinov, and factory #92 director, comrade Elyan, must organize production of 57 mm ZiS-2 anti-tank guns and ZiS-4 tank guns to replace 76 mm mod. 1942 divisional guns and F-34 tank guns, following this schedule:
1. April: 50 units
2. May: 150 
3. June: 250
4. July: 350
   and 500 units monthly starting in August. Of the units listed, 20% are ZiS-4 tank guns.
   TsAKB must complete blueprints by June 1st, 1943, and provide them to GAU for approval.
   Send four AT guns and four tank guns from the April production batch to GAU (comrade Yakovlev) for trials, issuing a report to GOKO within ten days.
3. The People's Commissar of Armament (comrade Ustinov) and TsAKB chief (comrade Grabin) must provide GAU with ideas regarding a powerful new corps gun with the qualities of an anti-tank gun based on the 107 mm M-60 gun and 100 mm B-34 naval gun. Also provide ideas for a new special tank, AT, and SPG gun that can penetrate 150 mm of armour at 30 degrees at a distance of 750-1000 meters.
   GAU must examine materials provided by NKV in three days and make a decision regarding experimental prototypes, reporting to GOKO along with NKV.
4. People's Commissar of Ammunition, comrade Vannikov, must introduce 57 and 76 mm subcaliber rounds into production, with the following production schedule:

	May	June	July	August
ZiS-2 shell	3000	10000	10000	15000
ZiS-3 shell	15000	30000	35000	40000

By May 1st, design a 122 mm HEAT shell and a simplified 152 mm AP shell. Within 10 days of the designs being ready, GAU must perform trials and create blueprints for mass production.

5. The People's Commissariat of Chemical Production (comrade Pervukhin) must provide the People's Commissariat of Coloured Metals, above current quota and with first priority, the following materials for production of subcaliber armour piercing shell cores, in tons:

	April	May	June	July	August
Sodium Carbonate	15	30	50	55	70
Hydrochloric acid	75	85	180	200	270
Soot	4	6	13	15	18

and shipment of plastic ballistic caps to the People's Commissariat of Ammunition, according to the following schedule:

	May	June	July	August
ZiS-2 shells	6000	15000	15000	20000
ZiS-3 shells	20000	40000	45000	50000

6. The People's Commissariat of Coloured Metals (comrade Lomako) must provide the People's Commissariat of Ammunition with cores made from hard alloys in the following amounts:

	May	June	July	August
For ZiS-2 shells	5000	13000	13000	20000
For ZiS-3 shells	17000	35000	40000	45000

Chairman of the State Committee of Defense, I. Stalin."

RGASPI 644-2-157

SU-85 and SU-57

I wrote about some of these light TDs before, but here is a document describing them in more detail.

"Report of results of a trip to the Molotov GAZ factory in the city of Gorkiy

Experimental work is being done on the following vehicles:

• SU-85: an 85 mm D-5S-85A gun on the SU-76 chassis
• SU-57: a 57 mm ZiS-2 gun on the SU-76 chassis
• KSP-76: a 76 mm ZiS-3 gun on the GAZ-63 chassis
• Automobile mount of a 76 mm ZiS-3 gun on a GAZ-AA chassis

1. SU-85 on a SU-76 chassis: Consists of an 85 mm D-5S-85A gun on a production SU-76 chassis. It differs in the following ways:

1. An 85 mm gun is mounted.
2. The engines are turbocharged to 85 hp.
3. Planetary final drives are used.
4. Shock absorbers are installed in the front and rear.
5. The rear armour hinges downwards.
6. The return idlers are removed, and replaced with a runner.
7. The size of the porthole is increased.

The tactical-technical characteristics of the vehicle are as follows:

1. Mass: 12 tons
2. Crew: 3
3. Length with gun: 5500 mm
4. Maximum speed: 35 kph
5. Average speed on dirt road: 20 kph
6. Average speed on highway: 28 kph
7. Ground pressure: 0.54 kg/cm^2
8. Effective hp/ton: 14.2

Armament

1. Gun: D-5S-85A
2. PPSh: 2
3. 85 mm shells: 40
4. Maximum gun depression: -5 degrees
5. Maximum gun elevation: +15 degrees
6. Horizontal traverse: +/-12 degrees
7. Bore axis height: 1670 mm
8. Periscopic sight: Hertz panorama
9. Telescopic sight: TSh-15

Engine

1. Type: GAZ-203F
2. Maximum hp: 2x85/3600
3. Gearbox: ZiS-5 type with reinforced roller
4. Final drive: 2-stage cylindrical pair with a planetary mechanism, ratio 1:7.8

Suspension

1. Tracks: T-70 type
2. Number of teeth on drive sprocket: 16
3. Type: Torsion bar, with additional shock absorbers on rear and front.

The other parameters of the SU-85 are identical to the SU-76. A prototype was manufactured and underwent trials. Trials were satisfactory. Assembly of a second prototype is in progress and will be delivered to trials on June 25th, 1944. In case of successfully completed trials, the factory can begin mass producing the vehicle without much difficulty in 0.5-1 month.

2. SU-57 on the SU-76 chassis: The prototype has been built. The electric firing mechanism has not been tested. The factory has scheduled gunnery trials."

CAMD RF 38-11369-486

World of Tanks: Today in History: Vasiliy Gavrilovich Grabin

One of the best known Soviet artillery engineers was born on January 9th, 1900 (December 18th, 1899 in the old calendar) in the Kuban region. In 1923, he graduated from the Petrograd heavy field artillery command school, and served in Karelia until 1926. In 1926 he became a student at the mechanical engineering faculty of the Technical Military Academy of the Red Army.

In November of 1932, Grabin was appointed the deputy chief of the Main Design Bureau #38, which developed barrelled artillery systems. In 1933, the bureau was disbanded due to Tukhachevskiy's fondness for recoilless guns. Grabin did not want to participate in projects that he thought had no future, so he was reassigned to Gorkiy (Nizhniy Novgorod today) in 1933, to the "Novoye Sormovo" artillery factory #92.

First, factory #92 only built cannons. It was in need of a design bureau. Grabin created such bureau, and became its chief. The design bureau of factory #92 produced many high quality artillery designs.

In 1942, Grabin, already a Lieutenant-General, became the chief of the Main Artillery Design Bureau, in Kaliningrad (Korolev today). He worked here for many years.

The sheer amount of material prevents us from talking about all of Grabin's guns, but we will examine several of them.

The gun of the famous T-34 was born in the design bureau of the Gorkiy factory: the 76 mm F-34. It was accepted in 1941 under the name "76 mm tank gun model 1940". Over 38 000 F-34 guns were produced before 1944.

The ZiS-4 was another one of Grabin's creations that was installed on the T-34. It was based on the 57 mm ZiS-2 gun, and started production in July of 1941, but was only produced in very limited numbers. Tanks armed with this gun fought in defense of Moscow in the 21st Tank Brigade.

In 1941, based on the F-32 and F-34 tank guns, Grabin's bureau designed a gun for heavy tanks, initially indexed F-27. This gun was renamed to ZiS-5, and adopted by the army under the name "76 mm tank gun model 1941". It was installed on KV-1 and KV-1S tanks.

In May of 1941, Grabin, under his own initiative, began development of the 76 mm ZiS-3 divisional gun. It consisted of a 76 mm gun barrel on the ZiS-2 gun mount. In June of 1941, the prototype was ready, entered trials in July, and was demonstrated to Marshal Kulik on July 22nd. Despite the gun's excellent performance, Kulik opposed its adoption. Grabin, due to his stubborn personality, decided to produce the gun anyway. The engineer's work did not go to waste, and the gun was adopted by the Red Army in February of 1942. This gun became not only the most numerous gun in the Red Army, but in the world. Over 100 000 barrels (including the ones installed on the SU-76 SPG) were produced. This gun was the first in the world that was assembled on a conveyor belt. From 1943, this gun became the main gun of divisional artillery, as well as anti-tank regiments.

We will cover one more of Grabin's guns, the 130 mm S-70. This was the first domestic gun with an automatic loading mechanism. The mechanized ammo rack held both shells and propellant. The gun was loaded with mobile carriages and a mechanical rammer. The S-70 reached a rate of fire of 5.5 RPM with the automatic loader and 1.1 RPM without. A small batch of guns was produced in 1948.

Original article available here.

Factory #174 Experiments

"I report that in order to complete the request of Marshal Kulik on the production of SPGs, I received and transferred to the Chief Engineer of the factory, Military Engineer 1st class comrade Ginsburg, the following:

1. 37 mm automatic AA gun model 1939 (ZiK-37) - 2
2. 76 mm tank gun model 1927/32 (KT-28) - 1
3. Blueprints for the ZiK-37 and KT-28.
4. Dimensional samples of ammunition for the KT-28 gun and 57 mm ZiS-4 gun.

Additionally, ANIOP transferred one T-34 tank with a 57 mm ZiS-4 gun to factory #174.

I received requirements for a 76 mm SPG, a 57 mm AT SPG, and a 37 mm AA SPG. In order to complete the design, I still require the following:

1. 76 mm AA gun model 1938 (4K)
2. Blueprints of the 4K AA gun.
3. Dimensional samples of ammunition for the 37 mm AA gun model 1939 (ZiK-37)

[Handwritten:] On the 3rd point, UVZA will send blueprints. On the 1st and 2nd point, UVZA knows nothing about that.

ANIOP gave us a T-34 without a TMFD telescopic sight for the ZiS-4 gun. 

Currently, the Chief Engineer has distributed tasks for design of SPGs to his subordinates, but the work is in the beginning stages. Meanwhile the due date for returning the T-34 (June 15th) has already passed. 

I ask to give an order to transfer the above items to the factory and extend the time for using the T-34 tank.

At the same time, I wish to know if there is a formal contract for the production of these SPGs, or if the factory agreed to fulfil Marshal Kulik's request without a contract.

Military representative UVNA GAU KA, Military engineer third class, Erofeev

June 15th, 1941"

CAMD RF 81-12104-112

Nothing too unusual in terms of SPG designs, but the T-34 with a 57 mm ZiS-4 is more interesting. It is unlikely that this is one of the 14 tanks identified in the article, therefore the amount of these vehicles increases to 15.

Soviet 57 mm Guns

The Red Army, in its anticipation of hilariously over-armoured enemy tanks realized that the penetration of the F-34 gun was lacking. That is why, in 1941, Grabin's 57 mm ZiS-2 gun was adapted to the T-34 (and, in theory, T-34M). A shorter version of the ZiS-2 gun was named ZiS-4, and put into the T-34. The resulting tank, currently known to many as "T-34-57", appeared in documents as "T-34 with 57 mm gun", "T-34 with ZiS-4", "T-34 tank destroyer", or any combination of the above. Since the F-34 was already capable of defeating any enemy armour at 2000 meters, not very many of these tanks were made. CAMD RF 38-11355-323 lists 10 such tanks being sent from factory #183 to Vladimir to form the 21st Tank Brigade.

ZiS-4 57 mm gun model 1941

T-34 model 1941 with a 57 mm gun

In 1942, the Tiger hit the battlefield, and GABTU suddenly remembered this thing they had going pre-war. The 57 mm gun program was revived. A new and improved ZiS-4 was designed to fit the new and improved T-34 model 1942 turret.

ZiS-4 57 mm gun model 1943

T-34 model 1942 with a 57 mm gun

Four experimental T-34 tanks were built in June-July of 1943. However, at that point, work on 85 mm tank guns began, so no one was quite sure what to do with these odd ducks. CAMD RF 38-11344-1755 tells of their uninteresting fate:

"According to the ciphertext from Major-General comrade Vershinin, four T-34 tanks with the ZiS-4 artillery system were sent to the Gorohovets proving grounds, where, after trials, one tank was sent to factory #92, and the rest sent back to factory #183.

Please advise what to do with these tanks."

Notice how the new gun is still "ZiS-4", and not "ZiS-4M". 

The tests at Gorohovets were concluded on September 15th. The above document is dated October 11th. The T-34 armed with the longer S-54 76 mm gun was tested at Gorohovets around the same time. At this point, the first T-34-85 was already being built by factory #183, so new 57 and 76 mm artillery systems for the T-34 were discontinued. A project to stick the ZiS-4s already produced into SU-76es was also launched, but didn't really go anywhere. 

However, despite the 57 mm gun never quite making it on a tank, it was quite handy in its ZiS-2 form as towed artillery. Here's how it performed against the Tiger, from CAMD RF 38-11377-12:

"Target: side. Distance: 800 meters. Result: penetration, 110 mm in diameter. A fragment, 190 mm by 210 mm broke off on the inside. The welding seam connecting the side and rear plates burst in an area 500 mm in length.

Target: side. Distance: 1000 meters. Result: penetration, 110 mm entrance, 140 mm exit. Fragment broke off on the inside, 140 mm by 110 mm."

The gun is more than capable of taking out the Tiger from the side. Let's try the turret.

"Target: commander's cupola. Distance: 1000 meters. Result: penetration, breach 85 mm by 75 mm. The cupola was torn off.

Target: turret. Distance: 1450 meters. Result: dent, 110 mm in diameter, 70 mm deep. A 20 mm cracked bump formed on the inside.

Target: turret. Distance: 1450 meters. Result: dent 49 mm deep, 125 mm in diameter, with a jagged surface. On the inside, a 15 mm bump.

Target: turret. Distance: 1450 meters. Result: dent, 110 mm in diameter, 15 mm deep."

The gun is less capable against the turret (although they probably should have closed in a bit after the first few bounces). Shooting at the cupola is an effective tactic.

"Target: upper front plate. Distance: 500 meters. Result: insignificant indent, the shell ricocheted into the driver's vision port.

Target: upper front plate. Distance: 500 meters. Result: dent, 90 mm in diameter, 20 mm deep. The welding seam is destroyed throughout its entire length. 

Target: lower front plate. Distance: 500 meters. Result: dent, 120 mm in diameter, 35 mm deep. Two 70 mm cracks in the dent. The welding seam is destroyed on a length of 500 mm."

Seems like the front is a tough nut to crack. The welding seams are failing one by one, as usual. With enough hits, the front plate is bound to fall off!

Conclusions: "As a result of shooting at the Tiger tank with the domestic 57 mm gun, it has been established:

a) The AP shell penetrates the 82 mm thick side at 1000 meters.

b) The AP shell does not penetrate the 100 mm thick front at 500 meters."

Not fantastic results, but not surprising. The results are better than the British 6-pounder gun of the same caliber, at least.

The Tiger II test document does not mention the 57 mm gun, but that doesn't mean it couldn't take one out. A Tiger II with numerous breaches from a 57 mm AT gun was displayed during an exhibition of captured vehicles.

The text reads: "Armour: 100 mm" on the turret and "armour: 85 mm" on the hull. Two arrows on the turret point at breaches, and are labeled "the armour was penetrated by a subcaliber 57 mm shell from an anti-tank gun".

Penetration, Part 2

I have already written an article on a very wide-spread penetration table. Here is a table for some lesser-known guns (regrettably, missing most of the ones I was interested in).

CAMD RF 38-11353-950

This document shows the penetrations of some pre-war guns, and their caliber, muzzle velocity, and shell weight. This table lists some guns we're seen before (ZiS-4, 45 mm tank gun, F-34), but some new ones. There is the DShK, whose practical penetration I covered here. The table gives it 25 mm at 0 degrees and 200 meters, and 10 mm at 30 degrees at the same distance. This seems pretty fair when compared to those tests.

Another interesting gun is the F-30. It was tested in the T-28, and never made it into anything in mass production. 100 mm at 1000 meters at 0 degrees and 90 mm at 30 degrees is around the same as the D-5-T. A lot of the time, different guns that use the same shell do not actually possess different ballistic properties, but are instead differentiated by cost, size, ease of use, etc.

We see another gun I covered next, the ZiS-6. The penetration against a 30 degree sloped plate is the same as in that document, but this document shows the penetration against a flat plate at that distance: 128 mm.

The gun after that is the M-10 on the KV-2. I can't imagine that it was used very frequently with AP, given how devastating its HE shell was. There is at least one case of KV-2s using concrete-piercing shells against tanks. This gun achieves 85 mm against a sloped plate at 1000 meters, and 90 against an unsloped plate. This is worse than the ML-20 152 mm gun in the other penetration table, which is expected, given the M-10's shorter barrel length.

CAMD RF 38-11353-951

Now we get into something really interesting: foreign guns. Since there was not yet a chance to discover the penetration of German guns firsthand, these are based on data from military intelligence. Let's take a look. Keep in mind that a) this data is from gathered intelligence and is bound to be approximate, especially considering that b) the Germans tested to a 50% penetration standard, and the Soviets to a 75% penetration standard.

The first entry is "Rheinmetall Borsig" 37 mm. The shell mass is reported as 0.665 kg, at 800 m/s. This penetrates 40 mm at 250 meters and 26 mm sloped at 30 degrees at 600 meters. The Germans' own data shows the 3.7 cm PaK 36 as having 31 mm sloped at 30 degrees of penetration at 500 meters. Projectile weight and muzzle velocity are pretty close too. 

The next gun is "Rheinmetall Borsig" 47 mm. I have no idea what this is supposed to be, but it doesn't penetrate very well, and this is at very close distances.

Next is an 88 mm AA gun. Apparently it shoots a 9 kg shell at 820 m/s, which is a little too light and a little too fast, but the penetration numbers given seem consistent with that other penetration table data. 

The next gun is a new one, "heavy gun", 105 mm, maybe a 10.5 cm FlaK gun. The one after is an "anti tank (and also AA) gun, exactly matching a 5.0 cm PaK 38.

After that, we see something interesting: a 66 mm light AT gun, penetrating 75 mm of armour at 800 meters, or 75 mm of sloped armour at 200 meters, firing a 4.5 kg shell at 850 meters per second. Perhaps this is data from some kind of 75 mm squeezebore gun. Or maybe a captured Czech gun? 

The last entry in the table is an 88 mm AT gun, which, for some reason  fires a different shell at a different velocity than the 88 mm AA gun, and also penetrates the same amount of armour at 100 meters, angled or not. 

Soviet Tractor Tanks

Armoured tractors have frequently shown up in the 20th century, both as improvised fighting vehicles built by militias or resistance movements, and as organized attempts at creating a cheap and dirty armoured vehicle for a real army. This article covers armoured tractors built in the Soviet Union as more or less organized production efforts.

Masttyazhart AA Daimler

In 1925, as a part of the Mechanization and Tractorization of the Army program, Masttyazhart (Heavy Artillery Workshops) installed a 76.2 mm Model 1915 AA gun on a Daimler tractor (the model was not specified). The gun could rotate 360 degrees, had an elevation of up to 75 degrees, and depression of 0 degrees. The tractor towed a cart with 192 rounds of ammunition and a crew of six. It could only fire while stationary, with spades deployed. The vehicle was not mass produced.

D-10

Image from Solyankin et al, "Soviet Light Tanks 1920-1941", Zeughaus, 2007

This tractor-tank was developed in 1930 in Moscow. It was based on the Kommunar 9GU tractor, with 6-16 mm of armour, 4 machine guns, and one 76.2 mm model 1927 regimental gun facing backwards. The tractor could achieve 9 kph with a 75 hp engine. It was designed as a support tank, with one variant (D-14) capable of carrying infantry in it. The off-road capability was good, but reliability, crew ergonomics, and vision for the driver were deemed unsatisfactory. It is interesting to note the presence of a commander's cupola, giving the commander excellent 360 degree view range. The tank was not mass produced. 

D-11

Image from Solyankin et al, "Soviet Light Tanks 1920-1941", Zeughaus, 2007

The D-11 was a similar project to the D-10, but based on the Caterpillar-80. It had the same armament, but a weaker 60 hp engine, and a smaller fuel tank. It was not mass produced for the same reason as the D-10. The failures of the D-10 and D-11 projects made the Red Army seriously reconsider the viability of future tractor-tank projects.

SU-2 and SU-5

Image from Solyankin et al, "Soviet Self Propelled Guns 1923-1941", Zeughaus, 2008

The SU-2 self propelled gun was developed in 1931, at the Bolshevik factory. A 76.2 mm model 1902 divisional gun was mounted on a Kommunar 9GU tractor, behind an armoured shield. The gun could rotate 360 degrees. The tractor chassis had to be reinforced, and the driver's seat removed, in order to fit this modification. Armour thickness of the hull was 10 mm. The 75 hp engine accelerated the vehicle up to 12 kph. One of these vehicles was built. The vehicle had a crew of five.

In 1932, another, project at the Bolshevik factory put a 76.2 mm model 1915 AA gun on the same tractor. To compensate for the extra weight, the vehicle had no armour, and had four spades deployed when firing. One of these vehicles was built and passed trials, but the project was not continued due to the insufficient capacity of the Kommunar chassis to support 76.2 mm guns. This vehicle was designated SU-5, not to be confused with the SU-5 light triplex on the T-26 chassis.

NI-1

Early NI tank. Due to the highly improvised nature of manufacturing, two NI tanks can look vastly different.

NI, or Na Ispug (For Fear) was an improvised armoured vehicle, produced in Odessa. A STZ-5 tractor was equipped 10-20 mm of armour, or even mild steel with wooden boards, which would protect it from bullets. Armament varied based on what was available. NI tanks went into battle with 37 mm or 45 mm guns, 1-2 DT machine guns, sometimes only with a pipe to simulate a cannon. Some sources say that a 76.2 mm model 1938 mountain gun was used. The idea of the tank was not to combat other tanks, but to combat infantry, unprepared for the arrival of tanks, and lacking anti-tank weapons. The loud noise produced by this contraption contributed to the psychological impact of the tank. 55 of these tanks were built. The name NI was given to the after the war. During the war, they are designated as "tractor-tank". Three NI tanks exist to this day, at least one a reproduction for movies.

HTZ-16

Reproduction of a HTZ-16 tank in Kiev

Kharkov's approach to an armoured tractor was similar, but more uniform. A STZ-3 tractor was chosen for the job. It was equipped with 10-25 mm of armour, a 45 mm gun for enemy tanks, and a DP machine gun for enemy infantry. The turret of the tank did not rotate. Unlike with the NI, the HTZ-16 was set to be mass-produced, but problems with supplies limited the total production run to 60 at Kharkov and 30 at Stalingrad. At least one tank made it through the war and returned to its life as a tractor.

SU-2-2

CAMD RF 38-11355-190, a record of a meeting on turning obsolete tanks into tank destroyers, proposes installing the 57 mm ZiS-4 tank gun and, 37 mm and 25 mm automatic AA guns in the STZ-5 tractor "with extended hull and ZiS-16 engine". Meeting notes from Factory #92 list "SU-2-2, 57 mm tank gun on the fast artillery tractor STZ-5" as a potential option for production. However, this option was not chosen.

Voroshilovets 105-K

The same document proposes installing an 85 mm AA gun on a Voroshilovets tractor. The project was deemed unlikely, but launched at Factory #8 under the index 105-K anyway. A prototype was built, but not mass produced, due to the army's lack of heavy tractors.

ZiS-30

The ZiS-30 project was created by mounting a ZiS-2 57 mm anti-tank gun on a T-20 Komsomolets artillery tractor. This vehicle had 10 mm of armour in the front, and 7 mm on the sides and rear. It could reach a speed of 40 kph. The center of gravity was very high, leading to a chance of flipping the tank if the gun was fired without spades deployed. 101 of these vehicles were assembled over the course of about a month, and one with a 45 mm gun. The ZiS-30 performed well in combat, due to its powerful gun. However, the T-20 tractor was no longer produced in 1941. There were no spare parts for vehicles that managed to survive combat. Today, no ZiS-30s remain.

SU-2S

CAMD RF 38-11355-238

Despite a similar name, this project has nothing to do with the SU-2. It was developed in the fall of 1941, ten years later, at the Chelyabinsk Tractor Factory. A Stalinets-2 tractor, with a torsion bar suspension, had a 122 mm M-30 howitzer installed, and was armoured with anti-bullet armour (the Soviet "anti-bullet" category encompassed 4-20 mm of highly hardened steel). However, ChTZ became the new home of the Kirov factory, and started producing KV tanks, which were more important than this improvised solution. The M-30 howitzer found its way to an armoured hull in a few months, but one from a real tank.

Stalinets Tank Destroyer

CAMD RF 38-11355-639, fragment

In 1942, two engineers from the Ural Heavy Machinery Factory proposed a tank destroyer project. They intended to arm a Stalinets-2 tractor with a ZiS-5 gun, in a fully enclosed armoured hull. The resulting vehicle would have a crew of 3 and a height of only 1.8 meters. With only 25-32 mm of armour, and a reduced mass of 6-7 tons, the tank could theoretically reach a speed of 40 kph. The project was technically sound, but Stalinets-2 tractors were not built since 1941, and no compatible chassis was currently produced for this vehicle to ever be built.

Penetration

If you read the World of Tanks forums, odds are you've seen this penetration table. Overlord even talked about it on his blog. For those unfamiliar with it, let me give you a quick translation. 

The column on the left is distance to target in meters. The first row lists the guns: "45 mm tank gun model 1938 on tank T-70", "57 mm gun ZiS-4 on tank T-34", "76 mm gun F-34 on tank T-34 and ZiS-3 on SU-76", "85 mm gun D-5 on SPG SU-85 and S-53 on tank T-34-85", "85 mm gun of increased power, experimental", "100 mm gun on SPG SU-100", "122 mm gun D-25 on tank IS and SPG ISU-122", "152 mm howitzer on SPG ISU-152" (ML-20), "122 mm gun of increased power OBM-50, experimental" (BL-9), "152 mm gun of increased power OBM-53, experimental" (BL-8, BL-10), "57 mm English gun" (6 pounder), "75 mm American gun on tank M3 Lee" (M2 tank gun), "50 mm gun Model 1938 on tank PzIII", "75 mm gun Model 1940 on tank PzIV", "75 mm gun Model 1942 on tank Panther", "88 mm gun on tank Tiger", "88 mm gun on SPG Ferdinand". 

The V0 value indicates the muzzle velocity of the shell. Under each gun name, there are two columns: one for an armour plate angled at 60 degrees from horizontal and one for an armour plate angled 90 degrees from horizontal. When two values are shown in one box, the numerator is the performance of a caliber AP shell, the denominator is the performance of a subcaliber AP shell. 

CAMD RF 81-12038-303

If you've seen it before, you also have heard criticism aimed its way. "Propaganda!" some people cry. "The 8.8L/71 penetrated 203 mm at 100 meters, not 168! This document is not to be trusted!"

They are wrong about the propaganda bit, as this was a classified internal document, used by engineers to analyze the required armour and firepower for future tanks. It would be pretty foolish to falsify these numbers. Besides, a dense table of data isn't exactly the best for propaganda material.

However, the 8.8L/71 did penetrate 203 mm of armour... when the Germans tested it. German penetration testing standards were different from the Soviets'. German penetration tests were performed with specially selected shells, against armour angled at 30 degrees. If a shell could penetrate the effective armour thickness 50% of the time (several times in a row, depending on the shell caliber), that penetration is recorded as how much that shell can penetrate.

Obviously, the Soviets didn't get courtesy shipments of special testing ammo, so they used whatever was captured along with German tanks. Therefore, these tests give a better indication of how a tank would perform on the battlefield. The Soviets had two penetration standards. When only one penetration value is shown, 75% of the shell fragments end up behind the armour plate. When two penetration values are shown, the two values are for 20% penetration (possible penetration) and 80% penetration (guaranteed penetration). So, as you can see, according to this data, while the 8.8L/71 could penetrate 203 mm of armour using special shells with 50% probability, it could only penetrate 168 mm using regular shells with 75% probability.

This document is very interesting, because it brings together most common guns of WWII (regrettably, some interesting ones are missing, like the 17 pounder or the Sherman's 76 mm gun) under the same testing conditions. This makes the comparison between the various guns much easier than having to pick through various sources, and then tring to figure out all the different test conditions.

Now, time to do some comparisons! You may have read a lot about the unprecedentedly devastating power of the Tiger's gun. However, it penetrates 120 mm at most. This is definitely high for WWII, but similar performance is reached by the Soviet 57mm ZiS-4, that was mounted on some T-34s since 1941, as well as the 85mm guns from the SU-85 and T-34-85. With APCR, even the ordinary T-34's 76 mm gun surpasses the Tiger in penetration (albeit at the expense of accuracy).

The Tiger's successor, the Tiger II, reaches better results with the 8.8L/71 gun, 168 mm. However, the D-25 gun on the IS-2 (which I compared to the 88 mm guns before) achieves nearly as much penetration, and the D-10T gun on the SU-100 (also tested on the T-34-85) surpasses it.

The Panther's long 75 mm gun also has very good penetration, and is comparable to the experimental 85 mm gun. Of course, the experimental OBM-50 and OBM-53 surpass all other guns on this table with huge penetrations of 230 mm and 244 mm, respectively. This would have been enough to take out a Maus tank, if Germany had ever sent any into battle.

In conclusion, the myth of superior German tank guns is, yet again, proven false.

See more penetration values in Penetration, part 2.