a 100 mm tube and the lower part of the conning tower's supporting structure was protected with 20 mm plates. Aft there was a lightly protected auxiliary control station with 50 mm sides. Between the middle and lower decks the funnel uptakes were protected by 100 mm of armor and between the upper and middle decks. A 125 mm upper and lower grating protected the boilers from shells and fragments entering through the uptake openings. The torpedo protection system was developed on the basis of model tests and full-scale trials using the incomplete hull of the prewar battlecruiser Kronshtadt and was expected to resist a torpedo warhead equivalent to of TNT. It was made up of an external bulge with four longitudinal bulkheads. The first was thick, the second was , the third was 50 mm and the fourth . Presumably the thinner thicknesses were at the ends of the ships where the bulkheads were squeezed together. The outer space was left empty, but the two middle spaces were filled with oil that was intended to be exchanged with sea water as it was consumed, and the inner space was also to be left empty. One curious feature was that the first and second bulkheads were concave in profile. Apparently this was believed to improve their protective qualities, although there is no indication of how it did this. "The total depth of the system was about amidships, which seems rather shallow." The triple bottom underneath the armored citadel was believed to protect the ship against a charge equivalent to of TNT below the ship's hull. Armament Rather than use the Tsarist-era MK-3-12 gun as originally planned, or use the 305-mm/54 guns ordered for the Kronstadts, it was decided in 1947 to adopt a new and more powerful 61-caliber gun of the same size that was to use three newly designed triple SM-6 turrets. Each individual gun weighed and the complete turret weighed . The guns could be depressed to −4° and elevated to 50° at a rate of 10° per second. Traverse speed was 4.5° per second and each turret was ordinarily remotely controlled from the More-82 main fire control director, but could be locally controlled if necessary. They fired shells at a muzzle velocity of to a maximum range of around using of propellant. Their rate of fire was 3.26 rounds per minute and 80 rounds were stowed aboard