Developed by the Grabin Central Artillery Design Bureau in the fall of 1943. The S-51 passed trials successfully in the spring of 1944, but never entered mass production.
Often nicknamed by the players as "The Unicorn" for the impressive long barrel gun it holds when aiming upwards, out of the box, it has the SU-14-1's upgraded gun. It's rather slow when you first get it, and performance will be sluggish, but once upgraded, its mobility kicks in. Most players agree that the S-51 is superior to the SU-14-1 for these reasons: its mobility (especially when relocating to avoid becoming a counter-battery target), its agility in running from danger, and faster traverse speeds in switching between targets. It also has a smaller profile than the SU-14, which helps it with camouflage.
S-51 starts with 152 mm BR-2 Howitzer, which considering its repositioning in 8.6, makes it comparable to the old SU-8. However the second gun, 203 mm B-4 is the cannon that your enemies will fear you for. It gives S-51 the ability to deal more alpha damage than any other Tier 7 SPG, and even deal one-shots to Tier 8 heavy tanks. On the downside, it has a very slow reload time and it is rather inaccurate. Its large splash radius will none the less ensure that your opponent receives at least some kind of damage. The 203 mm B-4 canon can only carry 12 shells, which in most cases is enough thanks to the low rate of fire. It can also fire AP shells, which some people may find handy in close quarters combat for their high damage potential and good penetration.
The S-51 leads to the SU-14-2.
Pros and Cons
- Agile and easy to relocate
- Fast turning speed
- Best alpha damage of its tier
- Very high splash damage from the 203 mm gun will almost always ensure you´ll deal damage to enemies even if it misses
- Excellent gun elevation and decent gun depression can hit tanks even behind some buildings or save you from tanks that get too close
- Gun range can cover entire map easily
- The camouflage is quite good until you shoot; it´s strongly recommended to put as first skill camouflage to make it still better
- Good credit income. Dealing over ~1300 damage is enough to give you enough cash for repair costs and new ammo.
- Very narrow gun traverse
- Very long reload time
- Very limited ammo capacity
- Slow aim time
- Below average accuracy
- Getting the best gun can take long (64k experience needed)
- Very expensive ammo
- Since this Artillery is researched directly from a Heavy Tank, new players that are inexperienced with artillery mechanics can find it frustrating to use due the long reload times and very low ammo capacity, many agree that using this tank requires a mandatory use of a Large-Caliber Shell Rammer and an Enhanced gun laying Drive module.
- When using this Artillery, its best to relocate after a shot, as the reload time is long and relocating prevents counter-battery fire from enemy artillery that may track your tracer, the relatively good agility of the S-51 makes relocation a fairly simple task.
- Its a good idea to have one or two AP shells, as they can save you from incoming scouts that trespass into your base or severely damage Heavy tanks like the E-75 for its consistent damage (assuming you don't miss).
- Patience is key to this Artillery; Having limited Ammo capacity, its best to shoot if you are sure that you may be able to hit the enemy, since shooting blindly will make you run out of shells easily, you have a long reload and each shell is expensive
- Many players consider the SU-14-1 a more dangerous SPG than the S-51 since that players who researched this come from a heavy tank, and thus are inexperienced in artillery mechanics. It is recommended to learn SPG mechanics, or, just get the SU-8 and use it as a trainer before selling it and buying the S-51.
- As stock it can hold the best gun, radio and engine already without having to get the Suspension, your top priority will be the 203 mm gun
- As of 8.6 engines are unique - the V-2IS has been replace for this tank.
- Get the radio as it gives you range
- Then get the suspension, as it gives you better turning speed and maneuverability and its relatively cheap to research
- Get the Engine
Within weeks, some preliminary drafts were presented from plant № 100 NKTP, CB Uralmash, and TsAKB. The first of them, created under the leadership of J. J. Kotin, was a self-propelled gun carriage with trailer that, in some ways, resembled the French GPF 194, but with a more powerful gun. Draft CB UZTM had two options; a 203-mm howitzer B-4 on the chassis of the KV-1S (modernized draft SAC U-19) or two 152-mm howitzers on two SU-122 chassis. Before using its gun, it was supposed to connect both chassis; preparation to firing was about 30-40 minutes, versus 20 minutes with the Kotin design. It is clear that the development of plant number 100 and UZTM won't give adequate fire support due to its technological complexity. In order to build a single prototype, only TsAKB submitted a draft SAU under the symbol "S-51". The chassis of the KV-1S was considered for the base of the S-51, but it was quickly discovered that the length of the support-surface was insufficient and needed adjustment: a modified version with 7 or 8 rollers. However, NKTP was reluctant to change its production because the amount of modifications required was relatively large, and the number of issued ACS was unlikely to be exceed several tens of units. To this end, it was decided to establish a howitzer on the chassis of an unaltered KV-1S anyways, which was not the best solution. The chassis did not undergo any major change, except for the engine. The tank turret was dismantled, and a 203-mm howitzer B-4 was mounted on the open gun-carriage. Because the weight of the 203 mm howitzer was slightly heavier than the weight of a fully-loaded turret, the full combat-load weight was almost 50 tons. Thus, it was not expected to have good mobility.
The first prototype of the S-51 entered factory tests in February 1944, conducted under the reduced program. However, interest in high powered artillery was so great that it was still not finished was transferred to ANIOP. Here, all of the major disadvantages of the S-51 were revealed. Because of the high line-of-fire when firing, the self-propelled chassis was strongly swayed by inertia and would move to a lateral displacement. The elevation angle was relatively small, and the recoil was so strong that the crew could not hold on their seats. The severe recoil, large size and weight of its projectiles, and the extreme discomfort for the crew would require the installation of a rammer/loader. In addition, the chassis of the KV-1S proved it was clearly not a good platform on which to install guns of this caliber. After comparing all the data obtained in the COD, it was felt that the S-51 still be sent to production, but to no success. First of all, the issue of using KV-1S chassis was resolved in December 1942: the required amount of modifications for heavy self-propelled guns was only possible with the serious alteration of serial machines. Another important reason was the lack of the B-4 howitzer, which was not in production-scale numbers.
In return, engineers and design bureaus TsAKB plant number 100 had developed a version of an SPG on the chassis of a heavy tank, with the installation of a 152-mm howitzer BL-2. A prototype self-propelled guns, named S-59, was made in early 1944 on May-June, and underwent range tests. There is some discrepancy in the data on the type of equipment. According to factory records, S-59 received the chassis and body from the IP-85, but according to a report on the tests, the self-propelled gun had the "improved chassis of the heavy KV tank ". However, when firing a full charge, the S-59 began to have problems similar to that of the S-51, so mass production of the unit was not raised. As a result, this direction in the development of ACS fire-power ended.Nevertheless, the projects of heavy self-propelled guns continued to appear until the end of the war. For example, on July 29 1944, head of the Leningrad branch TsAKB Igor Ivanov presented the "technical adjustment of the IEC preliminary draft of ACS", which was supposed to use the chassis of paired T-34 tanks and the 210 mm gun BR-17 or 208 mm howitzer BL-18 . Based on a draft presented a year earlier of the proposed CB UZTM, this ACS differed by a more simple design. This development by TsAKB aroused some interest in the leadership of the People's Commissariat of Arms, but the timing of the project was not realistic; a prototype self-propelled gun was required to be submitted not later than 30 September of that year, and thus failed at the challenge of Leningrad.