SU-122 Requirements

 "Approved by Deputy People's Commissar of Defense, Colonel General of Artillery, Voronov

October 17th, 1942

Tactical-technical requirements of a 122 mm self propelled howitzer on the chassis of the T-34 tank

1. Purpose of the self propelled howitzer

The self propelled howitzer is designed to accompany infantry and tank units, destroying dugouts and fortified firing positions with direct fire from short range or with indirect fire.

2. Requirements for the artillery component

The artillery component of the SPG is provided by the stock rotating part of the M-30 122 mm model 1938 howitzer. The mounting must meet the following requirements:

1. Practical rate of fire of no less than 10 RPM in a direct fire role.
2. Elevation of 25-35 degrees.
   
3. Depression of -3 degrees.
4. Traverse of +/- 10 degrees.
5. The recoil buffer must be armoured. The armour must be at least 12 mm thick.
6. The oscillating part of the howitzer with the recoil buffer armour must be completely balanced. Increase in effort required to aim cannot surpass 10%.
7. The height of the bore axis must be no more than 1500 mm. To achieve this, a cutout in the front of the SPG is permitted.
8. The gun port must be completely covered at a gun elevation of up to 12 degrees.
9. The gun mount must allow for comfortable loading at all angles of elevation and traverse.
10. The sight is the stock sight from the 122 mm M-30 howitzer with a Hertz panoramic sight.
11. The gunner's seat must rotate with the gun. The seat's rotation in relation to the panoramic sight and aiming flywheels must allow for comfortable operation.
12. The crew consists of five men, including the driver. All crewmen must have comfortable seats.
13. The gun must have the ability to be reliably fixed for travel, preventing horizontal and vertical movement.
14. Two PPSh submachine guns must be carried as auxiliary armament.

Ammunition Storage

 "#01725
June 9th, 1945

In accordance with your letter #843079s dated May 25th of this year, we present the following ideas regarding rational locations of ammunition in ammunition racks and painting of the racks with the goal of prevention of explosions.

For the SU-76

1. Given 35 round of HE, 15 AP, and 10 APCR, place:
1. 11 rounds of HE on the right side, 17 on the left side, 7 under the gun cradle.
2. 15 rounds of AP in the upper bustle.
3. 10 rounds of APCR in the lower bustle.

Street Fighter

 "Tuesday, March 20th, 1945

Bulletin of street fighting experience, a daily publication of the Red Army newspaper For the Destruction of the Enemy

Guards Jr. Lieutenant-Technician M. Litvinov
Guards Jr. Lieutenant-Technician N. Deryugin

Self propelled artillery in street fighting

Self propelled artillery plays a considerable role in street fighting. Only an SPG can approach a fortified building with enemy machine gunners and destroy it at point blank range. The enemy has felt the blows from SPGs and hunts them, sending out Panzerfaust troops and shooting them on the approach. Completion of the SPGs' objectives requires considerable experience from the drivers.

In this article, we would like to share the experience of SPG drivers in street fighting.

Heavy Tank Brigades

 "Report by the Commander of Armoured and Mechanized Forces of the Red Army

To the People's Commissar of Defense I.V. Stalin on the equipment of a heavy IS tank brigade

November 20th, 1944

I report that:

As per your orders, one heavy IS tank brigade with two regiments of 21 IS tanks each and one regiment of 21 ISU-122 will be ready by December 5th of this year.

There are 65 combat vehicles in the brigade in total.

Wider or Longer?

 

"Based on results of artillery trials of an IS-122 SPG in the amount of 438 shots (222 supercharged) the Gorohovets ANIOP makes the following conclusions:

• The 122 mm IS-122 self propelled gun passed proving grounds trials and can be accepted into mass production.
• The IS-122 has the following advantages over the IS-152 self propelled gun-howitzer, such as:
• Rate of fire is twice as high.
• Ammunition capacity is higher (30 rounds instead of 20 like in the IS-152).
• Muzzle velocity and penetration are higher (by 20%).
• The maximum range is longer (by 3 km).
• It is easier for the crew to work, load ammunition, and prepare for battle.
• Fire at moving targets is more effective."

Via Yuri Pasholok.

One Piece, IS-3 Edition

 "November 28th, 1945

To the Chief of the Main Artillery Directorate of the Red Army, comrade N.D. Yakovlev

People's Commissar of Armament comrade D.F. Ustinov

People's Commissar of Ammunition comrade B.L. Vannikov

Commander of Armoured and Motorized Forces comrade Ya.N. Fedorenko

RE: GAU letter #945369s dated November 22nd, 1945

I report that the Kirov factory produced an IS SPG equipped with an ammunition rack for single piece ammunition. This SPG will be sent to the GBTU proving grounds at Kubinka shortly.

At the same time, work was also conducted to place single piece ammunition in the IS-3 tank. It was not possible to achieve any kind of satisfactory results in this to date.

Only the SPG with ammunition racks for single piece rounds will be sent to trials.

People's Commissar of Transport Machinebuilding, V. Malyshev" 

Via Yuri Pasholok

Snow "Shoes"

The tank was born on the battlefields of WWI where it had to combat not only enemy fortifications, but also mud. Tanks were often lost not from enemy fire, but from being stuck on cross country terrain. Engineers and the military first started thinking about how to improve mobility of their vehicles. Further improvements focused on improving mobility in general, but advanced methods of driving on soft terrain did not progress past experiments. Engineers returned to the issue of improving off-road mobility in WWII. In addition to mud, tanks got a new enemy: snow. This issue was most prevalent on the Soviet-German front where there was more snow than anywhere else for obvious reasons.

Extended Magazines

"USSR NKO

Commander of Armoured and Mechanized Forces of the Red ARmy

July 19th, 1944

#511127

Trials were held to establish the possibility of increasing the amount of ammunition carried in SPGs, which increases the ammunition capacity of the ISU-152 and ISU-122 by 7 rounds and the SU-85 by 5 rounds if necessary.

Additional ammunition is to be carried in the following ways:

One Piece

 "To the People's Commissar of Ammunition of the USSR, comrade Vannikov
Chief of the Red Army GAU, comrade Yakovlev
Deputy Chief of Armoured and Motorized Vehicles of the Red Army, comrade Korobkov

In accordance with GOKO decree #6868s issued on February 4th, 1944, the People's Commissar of Tank Production instructed the Kirov factory to study the issue of single piece ammunition for the 122 mm D-25 gun.

ISU-122 Frontline Impressions

The Soviet ISU-122 heavy SPG is often overshadowed by its more famous siblings, the IS-2 tank and ISU-152 SPG. The similarity in the designs gave birth to the myth that the ISU-122 was an ersatz ISU-152 built due to a shortage of 152 mm guns. That is far from the truth. Let us try and figure out what crews of these tank destroyers valued the most, and what they would rather have changed.

Heavy Tank Destroyer

The ISU-152 is the best known Soviet heavy SPG. This was the most numerous heavy SPG in history and its career lasted for many decades, overshadowing its "little sister", the ISU-122. The vehicles had the same chassis and differed only in the gun (or rather just the barrel) and ammunition racks. It was the ISU-122 and not the ISU-152 that was the main product of the Chelyabinsk Kirov Factory. This was because the vehicles with 122 mm guns were meant to be heavy tank destroyers. Tank regiments that fought in IS-2 tanks were even reformed as artillery regiments with ISU-122 tank destroyers.

IS-6 Drama

"To GBTU representative, Engineer-Lieutenant Colonel comrade Markin

Having taken the post of the GBTU TU representative at factory #100 in April of 1944, I already reported that my work at the factory is made difficult because of the fact that the factory is hiding experimental work from me, which has now resumed at the factory. At first, this secrecy was obtained by organizing a special room, which only comrade Kotin and a short list of other people were permitted to enter. I was not included in this list (at the time, the design of the IS-6 tank was being kept secret from me).

T-34-85 Reliability, 1945

The service life of the T-34 tank continued to increase throughout the war. The engine could be expected to put out 250 hours of service by 1945, with individual drivers able to get to 300. These were not individual occurrences, as the 2nd Guards Tank Army's experience shows.

Heavy Tank Destroyers that Remained on Paper

The KV-14 (SU-152) SPG was accepted into service on February 14th, 1943. It was designed primarily to combat enemy fortifications, but its first use in combat pitted it against German tanks. Work on tank destroyers on the SU-152 chassis began in the spring of 1943. Even though none of these projects was implemented in metal, the work eventually led to the ISU-122.

Industrial Accident

"Unscheduled report of an extraordinary event

Unit: GBTU Scientific Research Proving Grounds

Region: MVO

Event: wound during trials

Time: 10:00 August 8th, 1944

Location: shooting range of the NIBT Proving Grounds, Kubinka station, Western Railroad

Victims:

Rank and position	Name	Year of birth	Nationality	Education	Social status	Party affiliation	Place of birth	Nature of wound
Sergeant Loader	Toldykin, Fedor Pavlovich	1924	Russian	7 grades	Kolkhoz farmer	VLKSM	Sorochkinsk, Chkalov oblast	Ragged forehead wound
Sr. Sergeant Gunner	Butorov, Ilya Innokentivich	1922	Russian	5 grades	Worker	VLKSM	Bysherovo, Buryat Autonomous Soviet Socialist Republic	Minor head bruise

Description of the event:

On August 8th, 1944, at 10:00 when testing the effect of the D-25 122 mm gun (#266-44) installed on an experimental ISU-122 #249 against armoured hulls, the gun fired unexpectedly when loaded during the fourth shot, as a result of which the recoil of the gun wounded the loader Sergeant Toldykin (ragged forehead wound) and gunner Senior Sergeant Butorov, who received a minor bruise on the forehead."

CAMD RF 81-12038-312 p.373

Pistol Power

Conservative elements within the tank corps favoured the Nagant M1895 revolver. It was relatively simple and could be fired out of a smaller pistol port than the TT. However, the Nagant took much longer to reload and could not use submachinegun ammunition in a pinch.

"For ISU-122 crews it is desirable to have a TT pistol, since the long loading time for Nagant revolvers puts the crew into a critical position. The limited amount of ammunition in a revolver causes frequent reloads. There is also much more ammunition for a pistol available inside the vehicle."

Via Andrei Ulanov.

ISU-122S Acceptance

"State Committee of Defense Decree #6430ss

August 22nd, 1944

Moscow, Kremlin

On the acceptance of the ISU-122S SPG with the 122 mm D-25S gun into service and into production 

The State Committee of Defense decrees that:

1. The ISU-122S SPG with a 122 mm D-25S gun designed by factory #9 in accordance with the tactical technical characteristics in attachment #1 is accepted into service.

Lethality in Berlin

Some interesting data from the 2nd Guards Tank Army gathered during their fighting in Berlin. Analysis of tanks that were badly damaged enough to have to be written off from their unit was performed at the repair base. There, a decision was made: either the tank is irreparable and is destined for the scrap heap or is salvageable, but only after refurbishment, and is thus sent to the factory. Unfortunately there are no notes that tell us why each specific type of tank typically became unsalvageable, but only a general rule of thumb: if the ammunition rack is hit, the tank blows up and is a complete loss. If the ammunition does not go off, then the tank will probably be suitable for refurbishment, even if there was a fire.

Type	Total	T-34		IS-2		M4A2		SU-76		SU-85		SU-100		ISU-122
		Irrep.	Maj.	Irrep.	Maj.	Irrep.	Maj.	Irrep.	Maj.	Irrep.	Maj.	Irrep.	Maj.	Irrep.	Maj.
75 mm shell	39	6	8	-	-	3	16	2	2	-	2	-	-	-	-
88 mm shell	27	7	3	7	-	4	4	-	-	-	-	1	-	1	1
100 mm shell	9	2	2	3	-	1	1	-	-	-	-	-	-	-	-
22 mm AA gun	5	-	1	-	-	4	-	-	-	-	-	-	-	-	-
Artillery total	80	15	14	10	-	12	21	2	2	-	2	1	-	1	-
Faust	47	16	2	2	1	13	8	3	-	-	-	1	-	1	-
Aircraft	4	-	-	-	-	-	2	-	-	-	-	-	-	2	-
Mines	4	2	-	-	-	-	-	-	1	-	-	1	-	-	-
Total	135	33	16	12	1	25	31	5	3	-	2	3	-	4	-