SU-122

Infobox Weapon
name=SU-122


caption=SU-122 SPH in Kubinka Tank Museum, 12 December 2006.
origin=Soviet Union
type=self-propelled howitzer
is_vehicle=yes
used_by=Soviet Union
wars=Eastern Front
designer=F. F. Pietrow
design_date=15 April 1942 - December 1942
manufacturer=UZTM
production_date=December 1942 - summer of 1944
number=1,150
variants=See variants section
length=6.95 m (22.80 ft)
width= 3.00 m (9.84 ft)
height=2.32 m (7.61 ft)
weight=30.9 tonnes (68,122 lbs)
suspension=Christie
speed=55 km/h (34 mph)
vehicle_range=300 km (186 mi)
primary_armament=122 mm M-30S howitzer
secondary_armament=none
armour=45 mm (1.77 in)
engine=diesel model V-2
crew=4
engine_power=500 hp (375 kW)
pw_ratio=16 hp/tonne

The SU-122 (SU-122 stands for "Samokhodnaya Ustanovka–122") was a Soviet self-propelled howitzer used during World War II. The number "122" in the designation stands for the caliber of the armament, the 122 mm M-30S howitzer.

Development History

The Soviet High Command became interested in assault guns following the success of German Sturmgeschutz III SPGs. Assault guns had some advantages over tanks. The lack of a turret made them cheaper to produce. They could be built with a larger fighting compartment and could be fitted with bigger and more powerful weapons on a given chassis. However, assault guns could only aim their weapons by turning the entire vehicle, and were thus less suited for close combat than tanks.

In April 1942, design bureaus were asked to develop several assault guns with various armament: 76.2 mm ZiS-3 divisional field guns and 122 mm M-30 howitzers for infantry support, and 152 mm ML-20 howitzers for breaking through enemy strongholds.

A prototype assault gun, armed with the 122 mm howitzer and built on the German Sturmgeschütz III chassis was designated SG-122. Only 10 of these were completed. Production was halted when the vehicle was judged to be unsuccessful and found to be hard to maintain.

Simultaneously, a SPG based on the T-34 tank was also developed. Initially the T-34's chassis was selected for the 76.2 mm F-34 gun. This vehicle, the U-34, was created in summer 1942 at the design bureau of UZTM (Uralmaszzawod - Uralsky Machine Building factory) by N. W. Kurin and G. F. Ksjunin. It was a tank destroyer with the same armament as the T-34 tank, but because of the absence of a turret, the vehicle was 70 cm lower, had thicker armour, and was 2 tonnes lighter. It did not enter production.

UZTM then worked on fusing features of the U-34 and the SG-122. Initial design work was completed between July and August 1942. The project emphasized minimizing modifications to the tank and the howitzer. It used the same chassis, superstructure, engine and transmission as the U-34 and was armed with a new 122 mm M-30S howitzer designed by F. F. Pietrow's design bureau. [http://www.zgapa.pl/zgapedia/SU-122.html Zgapedia] ] This vehicle also used the same gun bed cover and gun mountings as the SG-122, so as to keep the price low and simplify production. It had 45 mm thick frontal armour. The M-30S howitzer could be elevated or depressed between -3° and +26° and had 10° of traverse. The five-man crew consisted of a driver, gunner, commander and two loaders.

On 25 November 1942 the first U-35 prototype was ready. Trials ran from 30 November to 19 December 1942. The trials showed various faults in the design including insufficient gun elevation, flawed shell transferrer, poor ventilation for the crew compartment and the fact that the commander had to assist in operating the gun which made him unable to successfully carry out his other duties. The U-35 entered service with the Red Army as the SU-35 (later renamed SU-122) despite these faults.

Production SU-122s were based on an improved prototype built after the trials were conducted. They incorporated several modifications including slightly less angled front armour to ease production, modified layout of the fighting compartment (the locations of each crew member's station and ammunition racks were changed), fewer vision slots and a periscope for the commander. The first production vehicles were completed before the end of December.

Production history

SU-122 production began in December 1942 with 27 vehicles built that month. The original plan for production beyond that point was to produce 100 SU-122s each month. Production continued until the summer of 1944, by which time a total of about 1,150 SU-122s had been built.

ervice history

The first SU-122s produced in December 1942 were sent to training centers and two new combat units, the 1433^rd and 1434^th self-propelled artillery regiments. Initially, each of these mixed regiments consisted of two batteries with four SU-122s each and four batteries with four SU-76 tank destroyers each. Each regiment had an additional SU-76 tank destroyer as a command vehicle. It was planned to raise 30 self-propelled artillery regiments operating within armoured and mechanized corps. Fact|date=August 2008

In January 1943, the 1433^rd and 1434^th self-propelled artillery regiments were sent to the Volkhov Front near Leningrad as part of the 54^th Army. On 14 January they saw combat for the first time in Smierdny region. After that it was decided SU-122s should follow between 400 m and 600 m behind the attacking tanks; sometimes this distance was shortened to between 200 m and 300 m.

The use of SU-76 tank destroyers together with SU-122 proved unsuccessful. Based on combat experience, the organization of self-propelled artillery regiments was changed; the new regimental organization consisted of two batteries of SU-76 tank destroyers and three of SU-122s for a total of 20 SPGs. In April the organization of self-propelled artillery regiments was again changed. Separate regiments were created for SU-76 tank destroyers (light self-propelled artillery regiment) and SU-122s (medium self-propelled artillery regiment).

The medium self-propelled artillery regiment consisted of four batteries of four SU-122s each. Each regiment was also equipped with either an additional SU-122 or a T-34 for the commander and a BA-64 armoured car. This organization remained in place until the beginning of 1944 when the SU-122 started to be replaced by the SU-152, ISU-122 and ISU-152 heavy SPGs and SU-85 tank destroyers.

The SU-122 proved effective in its intended role of direct fire on strongholds. The anti-armour performance of the 122 mm howitzer was less than expected, so the new BP-460A HEAT projectile was developed and used from May 1943. However, this also didn't perform up to expectations.

At least one SU-122 was captured by the German Army.

A small number of SU-122s survived the war. Currently, only one example remains, on display in the Kubinka Tank Museum.

Variants

The SU-122 had no variants that went into mass production.

Towards the end of the production run, a prototype SU-122 was built with the same ball mantlet as the later SU-85s. .

U-122M

Even as the SU-122 was being mass-produced, its design was being refined primarily with an eye to reduce cost. Although the GAU RKKA artillery committee decided the M-30S howitzer would serve as an armament of SU-122, the weapon proved poorly-suited for an armoured vehicle. The howitzer took a lot of space and required both commander and gunner to operate it in order to fire. Because of this, in January 1943 work started on fitting the SU-122 with a different howitzer.

The prototype SU-122M was built in April 1943. It featured a bigger fighting compartment as well as an individual driver's hatch. The M-30S howitzer, mounted on the floor of the vehicle, was replaced by the more modern D-11 howitzer (a variant of U-11 howitzer). However, the SU-122M was not put into production due to a decision to proceed with the SU-85 instead.

U-122-III

Another attempt to create an improved SU-122 replacement was done by taking a SU-85 chassis and coupling it with the 122-mm D-6 howitzer, which was lighter and smaller than the U-11 howitzer. This was unsuccessful. Due to the unreliability of the howitzer's recoil mechanism and its poor anti-tank capabilities, all further design work on 122 mm self-propelled howitzers was cancelled.

References

*

External links

* [http://www.wwiivehicles.com/ussr/self_propelled_guns/su122.html WWII Vehicles]
* [http://www.onwar.com/tanks/ussr/fsu122.htm OnWar]

ee also

* List of Soviet tanks - covers all periods