ISU-122

ISU-122

SU-85M

ISU-122S

ISU-122

SU-85M

ISU-122S

USSR

III Rank

Battle rating:

AB	RB	SB
5.3	5.3	5.3

Class:

Tank destroyer

Research:20 000

Purchase:135 000

This page is about the Soviet tank destroyer ISU-122. For the version equipped with a D-25S cannon, see ISU-122S.

Description

The ISU-122 is a rank III Soviet tank destroyer with a battle rating of 5.3 (AB/RB/SB). It was introduced during the Closed Beta Test for Ground Forces before Update 1.41.

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 65 mm (7-69°) Gun mantlet case 100 mm Gun mantlet (0-45°)	75 mm (14-15°)	60 mm	30 mm

Notes:

• Suspension wheels are 20 mm thick while tracks are 30 mm thick.

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

122 mm A-19					Turret rotation speed (°/s)					Reloading rate (seconds)
Mode	Capacity	Vertical	Horizontal	Stabilizer	Stock	Upgraded	Full	Expert	Aced	Stock	Full	Expert	Aced
Arcade	30	-3°/+22°	-3°/+7°	N/A	6.16	8.53	__.__	__.__	12.19	26.00	_.__	_.__	20.00
Realistic					4.17	4.90	__.__	__.__	7.00

The ISU-122, like the ISU-152, is a vehicle created by adapting an artillery field gun design on an armoured vehicle. The A-19 gun has the same good ballistic characteristics as the 122 mm on the IS-2 (flat trajectory, high muzzle velocity, accuracy at long range) and the same available ammunition choice.

The gun stays reliably accurate until 1,300 m distance. Beyond 1,000 m your optics will limit your accuracy as your magnification is poor (unless you fire at huge targets like Ferdinand, Jadgtiger, Tiger II, etc.). The high muzzle velocity of your shells grants you pretty flat firing trajectories and thus helps fire at moving targets from a distance. In that regard, using the "sight control distance" feature can increase your chances of successfully hitting enemy tanks.

The gun has a limited traverse on the horizontal axis. That displacement is asymmetrical due to the commander's position limiting rotation towards the left side. This can make the tracking of a target difficult as the gun quickly reaches a stop. You should take that constraint into account when positioning your hull at a firing spot.

Additionally, the rotation speed is very slow compared to other tanks at the same rank or battle rating who can aim their gun in average 2 to 3 times faster than you do. Which means your targeting process will be longer than for other tanks if you aim to be accurate. Any enemy appearing outside of the area your gun covers will require hull movement and will make you restart your targeting process from 0.

Being originally an artillery field gun, the gun uses two-piece ammunition with projectiles and propellant bags. The breech mechanism was not designed to be operated by a limited crew inside a casemate, which explains the very long reload time (between 19 and 26 seconds, which is around 3 times longer compared to vehicles at the same BR).

Your recoil is important but not powerful enough to throw your gun off target after firing: the damping cylinders on the gun are too weak to absorb most of the recoil power and the suspension will absorb much of it. Your reload time being very long, the recoil is not as much of a handicap as it could be.

Ammunition

The available choice of ammunition focuses on heavily armoured targets:

• BR-471: APHE; an armour-piercing shell with high explosive mass and high muzzle velocity that will one-shot any tank that it penetrates.
• BR-471B: APHEBC; the same as the BR-471 but with increased penetration thanks to the ballistic cap. This shell can reliably penetrate the frontal glacis of a Panther from over 700m.
• OF-471: HE; for destroying open and lightly armoured vehicles. While it is a standard shell for a Soviet vehicle, prioritize using your heavy machine gun to deal with lightly armoured targets because of the long reload time of the ISU-122.

Penetration statistics
Ammunition	Type of warhead	Penetration @ 0° Angle of Attack (mm)
		10 m	100 m	500 m	1,000 m	1,500 m	2,000 m
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 (m/s)	Projectile Mass (kg)	Fuse delay (m)	Fuse sensitivity (mm)	Explosive Mass (TNT equivalent) (g)	Ricochet
							0%	50%	100%
BR-471	APHE	795	25.00	1.2	19.0	246.4	47°	60°	65°
BR-471B	APHEBC	795	25.00	1.2	19.0	246.4	48°	63°	71°
OF-471	HE	800	25.00	0.1	0.1	3,600	79°	80°	81°

Ammo racks

Ammo racks of the ISU-122

Full ammo	Ammo type	1st rack empty	2nd rack empty	3rd rack empty	4th rack empty	5th rack empty	Visual discrepancy
30	Projectiles Propellants	25 (+5) 25 (+5)	19 (+11) 19 (+11)	13 (+17) 17 (+13)	7 (+23) 9 (+21)	1 (+29) 1 (+29)	No

Notes:

• The ISU-122 uses two-piece ammunition, composed of propellant bags (orange) and projectiles (yellow). Both have separate racks.
• To go into battle with the right flank depleted of propellant bags (racks 1 to 3), pack 17 (+13) shells.

Machine guns

The 12.7 mm DShK heavy machine gun is located on a pintle mount and can act as both an offensive and anti-aircraft machine gun on the ISU-122, giving it protection against aircraft and lightly armoured vehicles. Best use is within 500 m against lightly armoured vehicles. The 360° movement allows you to point quickly your MG in any given direction. However, the position of the MG high on the casemate and the poor depression angle make it difficult to shoot a low-profile tank when it is close.

12.7 mm DShK
Mount	Capacity (Belt)	Fire rate	Vertical	Horizontal
Pintle	250 (50)	600	-5°/+85°	±180°

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).

Modules

Tier	Mobility		Protection	Firepower
I	Tracks		Parts	Horizontal Drive
II	Suspension	Brake System	FPE	Adjustment of Fire	BR-471B
III	Filters		Crew Replenishment	Elevation Mechanism
IV	Transmission	Engine

Pros and cons

Pros:

• Powerful cannon, can penetrate the majority of enemies it faces
• Great post-penetration damage
• No armour weak spots
• Good acceleration in reverse allows you to hide quickly

Cons:

• Slow reload
• Armour cannot stop most common cannons and penetrations are often lethal
• Like most Tank Destroyers, it lacks a turret and so its firing angles are restricted
• Breech gets damaged often
• Slow traverse means flanking attacks are lethal

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-122 SPG was created in 1943 based on the IS-1 with the 122 mm A-19 Mod. 1937 field cannon's tipping unit installed in its cabin. The cannon was mounted with an offset to the right from the hull's central axis. The driver's compartment was placed to the left of it. The weapon had a relatively low rate of fire, amounting to around 2.2 shots per minute. The barrel's length came to 46.3 calibres. Its armour-piercing round weighed 25 kg and had an 800 m/s muzzle velocity. Its ammunition load consisted of separately loaded shots. Its direct firing range came to 5,000 m, and its maximum range was 14,300 m.

The fighting compartment was also equipped with two 7.62 mm PPSh and PPS submachine guns with 1,491 rounds and 25 F-1 hand grenades. Starting from October 1944, a 12.7 mm DShK anti-aircraft machine gun was mounted on a bracket next to the commander's hatch. The machine gun had a 250 round ammunition complement. The crew consisted of four to five men. The crew housing in this vehicle was the same as in the ISU-152. Its armour protection was also the same as on the ISU-152. The cannon's gun mantlet had 100 mm thick armour.

The vehicle was mass-produced from April 1944 to September 1945 at the ChKZ factory in Chelyabinsk. In total, 1,735 of them were made.

The new SPGs were widely used in battles as tank destroyers and assault weapons in the final stage of the Great Patriotic War.

The long barrel length of the A-19 cannon installed in the fore of the armoured cabin limited the vehicle's manoeuvrability.

A small number of ISU-122s were modernised in 1958. Only their sights and radio sets underwent modernisation. At the beginning of the 1960s, the SPGs were removed from service in the Soviet Army.

Media

Skins

• Skin and Camouflages for the ISU-122 on live.warthunder.com.

Videos

ISU-122 Tank Review - NUSensei

See also

Vehicles equipped with the same chassis

• ISU-122 (China)
• ISU-122S
• IS-2 (Family)

Similar Soviet vehicles

• SU-57B
• SU-85
• SU-152
• ISU-152 & ISU-152 (China)
• SU-85M
• SU-100 & SU-100 (China)
• SU-122-54

Other Soviet vehicles equipped with a 122 mm gun

• KV-122
• SU-122P
• SU-122-54
• T-44-122
• IS-3
• IS-4M
• IS-6

Other vehicles of similar configuration and role

• Panzer IV/70(A)
• Panzer IV/70(V)
• Jagdpanther
• Ho-Ri Prototype
• CA Lorraine
• Ikv 103

External links

• [Wikipedia] ISU-122
• Tanks Encyclopedia - ISU-122 & 122S
• [Wikipedia] 122 mm gun M1931/37 (A-19)