Uralmash - 1 The Uralmash - 1 ( Уралмаш - 1 ) was a Soviet prototype self - propelled gun developed during World War II . It was a turretless , tracked armoured fighting vehicle designed by the Yekaterinburg - based Uralmash design bureau ( UZTM ) between autumn 1944 and spring 1945 . It used the chassis of the T - 44 medium tank and was intended to replace the SU - 100 which itself had only entered service with the Red Army in late 1944 . Two prototypes of the Uralmash - 1 with different armament were build in early 1945 , one with the 100 mm D - 10 tank gun , the other with the 122 mm D - 25S tank gun . While mass production was initially recommended , the end of the war with Germany in May 1945 eventually caused the project to be cancelled due to lack of necessity . If the Uralmash - 1 had entered service , the 100 mm variant would have been designated SU - 101 ( СУ - 101 ) while the 122 mm variant would have been designated SU - 102 ( СУ - 102 ) , in accordance with Soviet military nomenclature , where the " SU " - label stood for Samokhodnaya Ustanovka , or self - propelled gun . Development history . Work on the SU - 101 and SU - 102 at the Uralmash design bureau had basically started parallel to the creation of the SU - 100 , in summer 1944 . While the latter , based on the chassis of the T - 34 medium tank , proved satisfactorily in combat , its basic layout with crew compartment in the front and engine in the back was considered a flaw . The lowly mounted gun protruded far from the vehicle ' s front , which resulted in cumbersome maneuverabilty in urban or forested areas and could cause problems in undulating terrain , where the vehicle could potentially ram its own muzzle into the ground if not driven carefully . Additionally , the SU - 100 was very front heavy , which resulted in excessive stress on the forward road wheels , risking mechanical failure . Should the need for upgrading the vehicle with a bigger and heavier gun arise , all these problems were expected to be massively exacerbated . To address these deficiencies , UZTM designer N . V . Kurin had developed a number of preliminary designs of new self - propelled guns , using the chassis of different contemporary Soviet tanks , both with crew compartment in the front and in the back . In October 1944 the bureau offered five projects to the technical review board of the Commissariat of Heavy Industry for further examination : The technical review board recognized the SU - 100 - M - 2 and the SU - 122 - 44 , both based off the new T - 44 medium tank , as the most promising ones , and by order of directive № 625 to the tank industry , dated October 26 , 1944 to the plant of UZTM , ordered the finalization of the design , distribution of the technical drawings and preparation of one prototype each . While the SU - 100 - M - 2 proved to be compact and light enough for a medium tank chassis as well sufficiently armoured , the SU - 122 - 44 soon emerged as too big and too heavy . Thus , on March 7 , 1945 , by the commissariat ' s order № 107 , all work on the SU - 122 - 44 was terminated , whereas the SU - 100 - M - 2 was redesignated as " Uralmash - 1 " and the production of a first prototype by May 1 , 1945 was ordered . The designation Uralmash - 1 had already been used for a different self - propelled gun design in August 1943 , but that design had not been approved by the commissariat and was frozen at that time . In March and April 1945 , two prototypes were build , one equipped with the 100 mm D - 10 tank gun ( to be designated SU - 101 when inducted into actual service ) , the other with the 122 mm D - 25S tank gun ( to be named SU - 102 ) . Additionally , a third , empty , hull was made for armour tests under life fire circumstances . While the war with Germany had already ended in May 1945 , the prototypes were for the time being further tested by the UZTM design bureau during summer and autumn 1945 . Several problems emerged , among them was the heating up of the vehicle ' s interior due to insufficient engine cooling . This was especially severe in the case of the driver , who was seated next to the engine and whose working station heated up to unbearable temperatures in summer . Another problem emerging was the very crammed and uncomfortable crew compartment . Finally , the SU - 102 prototype faced structural problems , being not entirely suitable for absorbing the recoil of the powerful 122 mm gun . Yet these issues were deemed solvable and the vehicles were recommended for mass production after application of several modifications to address the prototypes ' problems . Eventually , however , the end of World War II finally led to the conclusion that the vehicles had by now become unnessecary , and in the end , the production of the SU - 101 and SU - 102 was terminated before it began . The SU - 101 prototype survived and is now preserved in the Kubinka Tank Museum in Moscow , where it is displayed as an indoor exhibit . Design characteristics . The Uralmash - 1 was a turretless casemate vehicle with a flat engine compartment in the front and a boxy elevated crew compartment in the rear , mounted on a suspension taken directly from the T - 44 medium tank . The main gun protruded from the crew compartment and arched over the vehicle ' s engine . Thus , even a long - barreled gun only slightly increased the overall vehicle length , improving maneuverability and eliminating one of the SU - 100 ' s major deficits . This layout was referred to as " of the Ferdinand sort " ( " по типу Фердинанда " ) in internal Soviet documents , referencing the German heavy tank destroyer Ferdinand faced by Soviet forces at that time , which was build in a similar fashion . The layout also spread the vehicles weight more evenly among the road wheels , addressing the mechanical issues faced by the front heavy SU - 100 . The crew of 4 consisted of vehicle commander , gunner , loader and driver . While the driver was seated in the front left side of the vehicle next to the engine , the rest of the crew was placed in the crew compartment around the main gun in the rear . Access to the vehicle was provided by a door in the rear of the vehicle . This additionally increased crew survivability , as in the case of an emergency evacuation the crew could exit the vehicle without exposing themselves to enemy fire as much as an evacuation through the roof hatches would require . The Uralmash - 1 ' s hull was made from plates of rolled homogeneous armour , welded together in a sloped fashion to give it improved protection . The frontal plates had a thickness of 90 mm , the sides 75 mm and the rear 40 mm . During firing tests with the empty hull , the vehicle ' s protection proved to be superior to the much heavier ISU - 152 tank destroyer as well as the IS - 2 heavy tank . The SU - 101 prototype with the 100 mm D - 10S gun came with a combat loadout of 35 rounds . While the horizontal gun traverse at 22 . 5° and the vertical elevation at 18° were entirely sufficient , the engine compartment limited the gun depression at a very meagre −2° , almost eliminating the vehicle ' s ability to go hull - down . The bigger 122 mm D - 25S gun of the SU - 102 prototype , with 28 rounds of ammunition , was even more limited in its gun traverse , not being able to depress the gun further than 0 . 24° with an elevation of 18 . 5° and horizontal traverse of 19° . The very limited gun depression is one of the fundamental drawbacks of a rear - mounted gun layout . The Uralmash - 1 ' s vehicle commander was additionally provided with a 12 . 7 mm DShK machine gun mounted in his roof hatch for use as an anti - aircraft weapon . The DShK ammunition loadout was 450 rounds . The Russian designation " SU " , meaning Samokhodnaya Ustanovka or self - propelled gun , is a rather diffuse term that was equally applied to vehicles which in combat fulfilled the roles of dedicated tank destroyer s , infantry - supporting assault gun s , and even indirect - fire artillery , i . e . self - propelled howitzer s . The SU - 101 / SU - 102 as a replacement for the SU - 100 , which was mainly used as tank destroyer , was potentially intended to fulfill the latter ' s role . The 100 mm D - 10S of the SU - 101 was a dedicated tank gun with capable kinetic energy armour - piercing rounds . The 122 mm D - 25S of the SU - 102 against that had originally been developed as an artillery howitzer to be used with high explosive rounds . However , in the course of the war , the gun had also proved to be a very effective anti - tank weapon , capable of knocking out even heavy German tanks , and armour - piercing kinetic energy ammunition had been developed to augment this battlefield role . As such the gun was already in use with the heavier ISU - 122 tank destroyer .