ISU-122S

ISU-122S

ISU-122

SU-100

ISU-122S

ISU-122

SU-100

USSR

IV Rank

Battle rating:

AB	RB	SB
5.7	5.7	5.7

Class:

Tank destroyer

Research:46 000

Purchase:155 000

This page is about the tank destroyer ISU-122S. For the version equipped with an A-19 cannon, see ISU-122.

Description

The ISU-122S is a rank IV Russian tank destroyer with a battle rating of 5.7 (AB/RB/SB). It was introduced during the Closed Beta Test for Ground Forces before Update 1.41. Compared to the ISU-122, the ISU-122S presents a better 122 mm cannon by allowing for faster reloads.

General info

Survivability and armour

Armour type:

• Rolled homogeneous armour
• Cast homogeneous armour (Gun mantlet)

Armour	Front	Sides	Rear	Roof
Hull	60 mm (75°) Front glacis 90 mm (31°) Lower glacis	90 mm	60 mm (50°) Top 60 mm (39°) Bottom	30 mm
Superstructure	90 mm (30°) Front glacis 100 + 65 mm (7-35°) Gun mantlet	75 mm (14-15°)	60 mm	30 mm

Notes:

• Suspension wheels are 20 mm thick while tracks are 30 mm thick.
• There is a plate of 40 mm thick under the gun mantlet, reinforcing the original 65 mm gun mantlet case.

Mobility

Game Mode	Max Speed (km/h)		Weight (tons)	Engine power (horsepower)		Power-to-weight ratio (hp/ton)
	Forward	Reverse		Stock	Upgraded	Stock	Upgraded
Arcade	39	15	46	739	992	16.07	21.57
Realistic	36	14		460	520	10	11.3

Armaments

Main armament

Give the reader information about the characteristics of the main gun. Assess its effectiveness in a battle based on the reloading speed, ballistics and the power of shells. Do not forget about the flexibility of the fire, that is how quickly the cannon can be aimed at the target, open fire on it and aim at another enemy. Add a link to the main article on the gun: {{main|Name of the weapon}}. Describe in general terms the ammunition available for the main gun. Give advice on how to use them and how to fill the ammunition storage.

D-25S is the same gun as a D-25T but got designated "samokhodnaya" or in other terms self-propelled for use in the SU-122S.

122 mm D-25S					Turret rotation speed (°/s)					Reloading rate (seconds)
Mode	Capacity	Vertical	Horizontal	Stabilizer	Stock	Upgraded	Full	Expert	Aced	Stock	Full	Expert	Aced
Arcade	30	-__°/+__°	±___°	N/A	__.__	__.__	__.__	__.__	__.__	__.__	__.__	__.__	__.__
Realistic					__.__	__.__	__.__	__.__	__.__

Ammunition

Penetration statistics
Ammunition	Type of warhead	Penetration in mm @ 90°
		10m	100m	500m	1000m	1500m	2000m
BR-471	APHE	205	201	183	162	144	128
BR-471B	APHEBC	205	203	191	178	166	155
OF-471	HE	37	37	37	37	37	37

Shell details
Ammunition	Type of warhead	Velocity in m/s	Projectile Mass in kg	Fuse delay in m:	Fuse sensitivity in mm:	Explosive Mass in g (TNT equivalent):	Normalization At 30° from horizontal:	Ricochet:
								0%	50%	100%
BR-471	APHE	795	25	1.2	19	246.4	-1°	47°	60°	65°
BR-471B	APHEBC	795	25	1.2	19	246.4	+4°	48°	63°	71°
OF-471	HE	800	25	0.1	0.1	3,600	+0°	79°	80°	81°

Machine guns

Offensive and anti-aircraft machine guns not only allow you to fight some aircraft but also are effective against lightly armoured vehicles. Evaluate machine guns and give recommendations on its use.

12.7mm DShK
Pintle mount
Capacity (Belt capacity)				Fire rate (shots/minute)	Vertical guidance	Horizontal guidance
250				600	N/A	N/A

Usage in battles

Describe the tactics of playing in the vehicle, the features of using vehicles in the team and advice on tactics. Refrain from creating a "guide" - do not impose a single point of view but instead give the reader food for thought. Describe the most dangerous enemies and give recommendations on fighting them. If necessary, note the specifics of the game in different modes (AB, RB, SB).

Pros and cons

Pros:

• Deadly cannon provides superior one-shot capacity with any target upon penetration. The improved firerate increases its killing potential even more.
• Powerful stock AP penetrates up to 205mm which is very effective in a full uptier. For example the weakspots of the early Centurions, Ferdinand, Tiger II H can all get penetrated with ease.
• The huge gun mantlet and its complex armor is capable of deflecting quite some shells sometimes.
• 30mm roof armor resists popular aircraft weapons well, like the 12.7mm M2 with ground target belt and the MG 151.
• All-round protection provides good resistance against flanking SPAAs. The M19 / M42 are very common flankers.
• 14 km/h reverse speed allows it to retreat from danger quickly

Cons:

• Reload time of 19s is still quite long, demanding precise aiming which isn't very beginner friendly.
• Front armour is only 60-100mm and is not well angled. Gets penetrated easily by common guns at the BR, like the 76mm M1, 17 pdr, 75mm and 88mm.
• Closely packed crew all easily get killed when an explosive shell penetrates.
• Very inadequate gun depression of -3° combined with the sluggish mobility makes it only capable of fighting in urban (flat) areas, but never the hills.
• Turretless layout and the sluggish mobility makes it very vulnerable to surprise flankers, for example the infamous M18, T20, T25 and Puma.
• Gun breech often gets damaged while under enemy fire.

History

Development

When the ISU-152 began production in 1943 with the large 152 mm ML-20S gun, production of the chassis and hull soon exceeded the supply of the ML-20S gun, which caused a decrease in the production of self-propelled guns for the Soviet military. It was determined to speed up self-propelled gun production, the ISU chassis were to be mounted with the 122 mm A-19S gun. Work on this mounting already began before the supply issue in December 1943 at the Chelyabinsk Kirov Plant (ChKZ), which had a design team simply take the ISU-152 chassis and hull and only changing out the armament with the 122 mm gun, but this prototype - Object 242 - was not immediately put into production despite successful testings. When the supply issue arose, the prototype was then adopted by the Soviet Defense Committee for increased production and also that the 122 mm gun had better accuracy against tanks than the 152 mm gun. The ISU armed with the 122 mm gun, designated the ISU-122, began production in April 1944.

Upgrade

The original ISU-122 is equipped with the 122 mm A-19S gun, which had a firing rate of 1.5 to 2.5 shots per minute due to its manual-piston breech. An attempt to fix this was a modernized A-19 gun called the D-25. The D-25 didn't see instalment onto the ISU-122 for a while due to prioritization on the IS-2 tanks, but it was available for use on self-propelled mounts after September 1944 as the D-25S. The ISU-122 prototype mounting the D-25 gun was called Object 249 which was successfully tested and an improvement over the A-19 gun with an increased firing rate of 2 to 3 shots per minute with one loader and up to 4 shots per minute with an additional loader in the crew. The D-25 also exploited the use of a muzzle brake in order to reduce the recoil forces on the gun, so the recoil buffer on the D-25 was much smaller than the A-19, which helped reduce the size of the gun and improved crew workspace in the self-propelled gun. Object 249 was then adopted as the ISU-122S, which entered production side by side with the ISU-122 u and both were produced up until the end of 1945. ChKZ produced both vehicles during the war and manufactured 1,735 ISU-122s (April 1944 - December 1945) and 675 ISU-122Ss (September 1944 - December 1945).

Combat usage

The ISU-122 were organized in units in a similar fashion as the ISU-152. The focus was made to not mix the two vehicles in the same regiments or brigades due to logistical reasons with ammunition and ballistic differences in indirect fire, but some units were equipped with both vehicles anyways. Like the ISU-152, the ISU-122 proved to be a very powerful multi-purpose vehicle as an assault gun, self-propelled artillery, and tank destroyer. The 122 mm gun on the ISU-122 allowed it to engage armour and fortifications with heavy armour-piercing round and a large high-explosive round. The primary role of the ISU-122 was as a tank destroyer due to the gun's superior ballistics compared to the ISU-152's, which large calibre size more suited its role as an assault gun. The ISU-122 did participate as an assault gun role in urban combat to support the infantry, but the lack of rotating turret and long barrel length restricted its manoeuvring and ability to engage all enemies in a large angle. Nevertheless, commanders found the ISU-122 as a very good assault gun. Usage of the ISU-122 in an indirect firing role as a howitzer is rare, but when used could fire up to 14 kilometres away. Usage as an artillery piece is more likely during a rapid offensive where towed artillery behind the lines is unable to keep up with the advancing infantry lines.

In-game description

The ISU-122S self-propelled gun was created in April 1944 as a modernised variation of the ISU-122 SPG. It differed from the latter in that it was equipped with a 122 mm D-25S Mod. 1944 cannon with a wedge-type semi-automatic breech block and a muzzle brake. The barrel's length came to 48 calibres. The height of its firing line came to 1,795 mm. The vehicle had a five-man crew and its crew housing was the same as in the ISU-122. The use of this cannon increased its rate of fire in combat from 2.2 to 3 shots per minute. The cannon's new compact recoil mechanisms and breech housing provided better working conditions for the combat crew. Artillery superiority over the enemy had been absent for some time, but the use of the D-25S cannon brought it back. It had higher combat characteristics than the German 75 mm and 88 mm weapons, and penetrated enemy tank armour at a range of up to 2,500 m. In urban battles however, the 122 mm cannon's barrel length often prevented the vehicle from manoeuvring in tight spots.

From August 1944 to September 1945, the ISU-122 with its A-19 cannon and the modernised ISU-122S with its D-25S cannon were produced in tandem, as the 122 mm D-25S cannon supply was insufficient to furnish all the SPGs. By the 1st of June 1945, 475 ISU-122S SPGs were built and used in battles in the final stage of the Great Patriotic War. In total, 675 of them were made in their mass production period.

ISU-122S SPGs were used across the entire functional scope of self-propelled artillery application. It was used as an assault weapon in breaking through fortified zones and in urban battles, but with reduced effectiveness in comparison to the ISU-152. On the whole, the SPG was highly regarded in this role as well. In the middle of the 1960s, the SPGs were removed from service in the Soviet Army.

Media

Skin and Camouflages for the ISU-122S in Warthunder Live.

See also

Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:

• reference to the series of the vehicles;
• links to approximate analogues of other nations and research trees.

External links

• [Wikipedia] ISU-122