Specification Crew : 5 Engine power : 600 hp Combat weight : approx 43,000 kg (94,815 lb) (later 52,000 kg (114,660 lb) Max speed : road 35 km/h (21.74 mph) Range : 335 km (208.03 miles) Length : 6.68 m (21.92 ft) Width : 3.32 m (10.89 ft) Height : 2.71 m (8.89 ft) Main gun : 76.2 mm Armour : 25 mm (0.98 in) to 75 mm (2.96 in) (later 130 mm (5.12 in)

The T-100 heavy tank was supposed to be the successor to the T-35.It had two turrets one with a 76.2 mm gun the other with a 45 mm (1.78 in) gun , but it was an unwieldy beast and was passed over in favour of a simplified heavy tank which became the KV-1. The first KV-1s were prone to clutch and transmission faults which took time to eliminate.The main armament was a 76.2 mm gun but although the armour used was the thickest that could be produced at the time it was still considered insufficient , a drawback which was overcome by adding sheets of applique armour to the front hull and turret.Later improvements included a longer-barrelled 76.2 mm gun , and the welded turret was provided with a cast steel component.KV-1s were continually up-armored to make them virtually invulnerable to German anti-tank guns.Yet the weight of all this extra armour was not compensated for by any added power from the engine which remained unchanged. The KV-1 remained in production until 1943.By then production was switching to the KV-85 which had an 85 mm (3.35 in) gun in a new turret the same combination being adopted for the T-34/85.Only 130 KV-85s were produced.