SU-122-54

SU-122-54 -Assault gun/tank destroyer version built in limited numbers from 1949 onwards through the fifties on T-54 chassis, armed with a 122 mm D-49S gun, two 14.5 mm heavy machine guns and fitted with a commander’s optical rangefinder sighting system. Support vehicles – a number are based on or use the T-54 chassis: the BTS-1 ARV, the MTU-1 AVLB and the BMR, T-54/PT-3, T-54/PT-54, T-54/PT-54M, T-54/PT-55, T-B4/KMT4, T-54/KMT-4M, T-54/KMT-5 and T-54/KMT-5M mine clearing vehicles. Plus the T-54/BTU and T-54/BTU-55 dozer tanks.

Also known under designation IT-122, the SU-122-54 was based on the T54 chassis. Developed started in 1949, with a goal to design a long-range tank destroyer. Between 1955 and 1957, 77 vehicles were built with minor differences between production lots (different commander’s cupola etc.). The SU-122-54 had a modified T-54 chassis, with small spaces between the first, second and fourth pair of wheels and a large gap between the third, similar to the T-62’s and a superstructure, built into the hull, housing the 122 mm M-62-T gun for which the vehicle carries 32 rounds. The secondary armament consisted of two KPVT heavy machine guns, one mounted as an anti-aircraft machine gun near the commander’s hatch and the other mounted coaxially with the main gun. The vehicle carried 600 rounds for the machine guns. The main gun has a fume extractor positioned right behind the muzzle brake, although some vehicles were built without fume extractor. Other variations included a different commander’s copula. The SU-122-54 was rarely observed during its service life in the 1950’s and early 1960’s and became generally known only after ARV versions (designated TOP) were seen during Red Square parades during the 1970’s with the armament removed and the front glacis plated over. In 1954 the SU-122-54 was experimentally tested with a more powerful 122mm M-62S tank gun, but this version did not reach series production.

SU-122-54 Modifications

The SU-122-54 was an amorphous design. It is clear from the small series produced that the overwatch role for which the vehicle was designed was in of itself greatly changed due to the rapid progress of rocket technology.  The SU-122-54 underwent capital repair in 1958, after most vehicles had been in service for only two-three years. Modifications included the provision of an R-113 radio station and a TPU-120 laryngaphone system as replacements for the 10RT-26 and TPU-47 respectively.

Back in 1952, some three years before the SU- 122-54 entered series production, and even as the five trials prototypes of the 122mm D-49 tank gun were being produced at Plant No.9 in Sverdlovsk, the OKB at Plant No.172 in Perm began work on a more powerful weapon developed for heavy tanks such as the T-10. It was also a potential replacement for the 122mm D-49 on the SU-122-54 and the D-10T on the T-54 series.

The tank and self-propelled gun versions of the new weapon were developed in parallel under the respective designation M-62T and M-62S. Two prototypes of the M-62S were completed in the autumn of 1954, but work on the self-propelled gun version of the weapon was interrupted on August 20, 1953. Work on the 122mm M-62T tank gun version of the weapon continued, the prototype 122mm M-62T being completed in November 1953.

After considerable testing and further development, the modified M-62T2 tank gun entered series production in 1957 as the main armament on the T-10M, the last series production Soviet heavy tank. The main distinctive feature of the 122mm M-62 series tank gun was the use of a multiple baffle muzzle brake.

After a hiatus of one year, work on the 122mm M-62S self-propelled gun variant of the weapon recommenced at the end of 1954. An SU-122-54 prototype armed with the 122mm M-62S was presented to GAU (the Chief Artillery Directorate) in September 1955; however the 122mm M-62S armed version of the SU-122-54 was not accepted for series production and did not enter service with the Soviet Army. 

For many years there were persistent rumours in the west of the existence of an IT-125 or IT-130 self-propelled gun, based on the same T-54 chassis as the SU-122-54 or that of the T-62. There were such design projects, which contemplated arming the vehicle with the 130mm M-65 tank gun as used on the concurrent Obiekt 277, 278, 279 and Obiekt 770 heavy tank prototypes, and latterly the 125mm D-81T or 2A46-1. These were developed for the T-64/72 during the later years of the SU-122- 54’s service life, but no prototypes are known to have been built.

SU-122-54 description

The SU-122-54 was based on the T-54A main battle tank and its mechanical components, but with a reconfigured road wheel layout, with the front three wheel stations being spaced to better distribute the weight of the forward mounted casemate fighting compartment and armament. Due to its modified road wheel configuration, the SU-122-54 was for many years misidentified in western intelligence reports as being based on the T-62 chassis.

The hull and casemate superstructure was produced from rolled armoured plate and was of welded construction throughout. The armour was well sloped, with the single piece frontal glacis and casemate superstructure heavily interlocked armour plate angled at 51degrees. The super- structure sides were also steeply sloped, with the casemate rear also set at an angle.

The SU-122-54 had a combined driver-mechanic and fighting compartment, with a bulkhead separating the fighting compartment from the rear engine and transmission (MTO) compartment.

The SU-122-54 had a classic self-propelled gun crew configuration, with the commander, gunner and two loaders also being located in the fighting compartment. The SU-122-54 had a total crew of five. The driving-mechanic’s position on the SU- 122-54 was unusual, as he was seated high up on the right side of the vehicle. There was no hatch to open in the glacis armour giving natural vision and the driver thereby relied on two forward facing and one side facing episcopes to manoeuvre the vehicle. As the SU-122-54 was intended for long-range fire support, the driver’s relatively blind driving position was not considered a major detriment.

The internal construction of the 122mm D-49 barrel, the ballistic properties and ammunition types available for the SU-122-54 were as for the D-25T tank gun as fitted to the IS-2 / IS-3 heavy tanks and the ISU-122 self-propelled gun, but with a longer calibre length and strengthened barrel.

The separate loading ammunition was time consuming to load but still less cumbersome in a confined space than for-instance the 100mm ammunition used on the SU-100. The SU-122-54 was provided with an electro-mechanical rammer, which gave the vehicle a for the time significant rate of fire of five-six rounds per minute. On early examples of the SU-122 a compressed air system was used to extract fumes from the barrel after firing; this was modified to a conventional barrel mounted fume extractor on later models. The front mounted D-49 armament was protected by a cast mantlet sometimes fitted with a canvas shroud.

The vehicle was provided with a specially developed TSh2-24 telescopic sight for direct fire to a theoretical range of 6,000 metres and an S-71-24 / S-72-24 mechanical sight with panoramic view for indirect artillery fire from a closed down position to a maximum range of 13,400/14000m should the need have ever occurred.

The commanders’ cupola was fitted with a TKD- 09 stereoscopic rangefinder. Gun traverse was 16 degrees (which though limited was not such a disadvantage considering the vehicle’s intended long range anti-tank role) elevation was approximately 16 degrees and gun depression – 4 degrees, which gave the vehicle reasonable anti-tank capability on reverse slopes and in when dug-in.

The co-axial 14.5mm KPVT machine gun was fitted with an automatic reloading system, while a 14.5mm KPVT anti-aircraft machine gun was mounted over the loader’s hatch, with a total 600- round ammunition complement provided for the secondary weapons.

The SU-122-54 initially used same ammunition as the 122mm D-25T, including the OF-471 HE-Frag, Br-471 and latterly the Br-471B anti-tank rounds, with a 35-round ammunition complement.

In addition to anti-tank rounds intended for the close fire support role, the 122mm D-49 could fire howitzer ammunition from the 122mm M-30 and D-30 towed weapons. The Br-471 armour-piercing round could penetrate 130mm of vertical armour at 1000m, and 100mm at 2000m, the later Br- 471B round could penetrate 145mm and 125mm respectively, with 25mm less armour penetration where the armour slope was 60°. The SU-122-54 was sighted to 3000m, but in Europe the undulating and forested terrain would have negated the SU-122-54s long-range effectiveness.

The SU-122-54 was not exceptionally armoured, reflecting its long-range stand-off role, however the frontal armour basis was a heavily sloped 100mm with 80mm on the superstructure sides, so it was more than adequately protected for a tank destroyer based on a medium tank chassis.  

The SU-122-54 was powered by a standard V-12 model V-54 diesel engine from the T-54, developing 520bhp at 2000rpm, coupled to a five-speed gear- box and planetary transmission. With a combat weight of 36.4 metric tonnes, the SU-122-54 could travel at a maximum road speed of 48km/hour, with a significant range of 400km.

Leave a Reply