After the Battle of Kursk it was realized that larger guns than 85 mm were needed. Kotin's team at Zavod Nr 9 initially placed an 85 mm gun in the IS series but it was then determined that a 100 mm or 122 mm gun was needed. The 100 mm BS-3 and 122 mm A-19 were put through tests in November 1943. The 100 mm was better at armor penetration but the 122 mm could rip off the armor of a captured Panther. The 122 mm was selected as it was available and the 100 mm was in very short supply.
Based on the IS-1 with a longer turret to accept the 122 mm, which was designed by General A. A. Petrov. Initially had a single chambered muzzle brake which later became a double chamber after a test which almost fatally wounded Marshal K. E. Voroshilov.
The A-19 122 mm gun was based on a naval gun. The ammunition was in 2 parts which slowed it's loading. An IS-2's crew could fire around 2 or 3 rounds a minute. In 1944 the 122 mm D-25T gun was installed which had a better breech which helped its performance.
The IS-2 had a cast hull front which was uniformly sloped, not bent as in the IS-1. The better sloping provided better protection without an increase in weight. The IS-2 could now withstand a direct hit by a 88 mm AP round at over 9,144 yards / 1,000 m.
crew: 4
weight: 101,963 lb
Length w/gun:31' "
Length w/o gun:21' 10"
Height:8.9'
Width:10' 1.6"
Ground clearance:13.75"
Ground contact length:14' 3.25"
Ground pressure:11.25 psi
Main:122 mm D-25
MG:3: 7.62 mm DT MG
Hull Front, Upper:4.3"
Hull Front, Lower:90-95mm
Hull Sides, Upper"3.5"
Hull Sides, Lower:90mm
Hull Rear:2"
Hull Top:20 - 30mm
Turret Front:3.9"
Turret Sides:3.7"
Turret Rear:90mm
Engine (Make / Model)
V-2-IS
Bore / stroke
4 stroke
Cylinders
V-12
Net HP
600 @2,000 rpm8
Power to weight ratio
11.3 hp/ton
Transmission (Type)
8 forward, 2 reverse
fuel Quantity
217 gallons, 158 gallons + 104 gallons in auxiliary
speed: 37 kmh
