at a muzzle velocity of . Their effective anti-aircraft range was . Fire control Each main gun turret was given a DM-12 rangefinder for use in local control, but they were generally controlled by one of three KDP-8 fire-control directors. These had two stereoscopic rangefinders, one to track the target and the other to measure the range to the ship's own shell splashes. Two of these were protected by of armor and were mounted atop the rear superstructure and the tower-mast. The other was mounted on top of the conning tower and was protected by 50 mm of armor. They used a TsAS-0 mechanical computer to generate firing solutions. Four KDP-4t-II directors, with two rangefinders each, controlled the secondary armament. One pair was on either side of the tower-mast and the aft pair was on each side of the aft funnel. Three SPN-300 stabilized directors, each with a 4-meter rangefinder, controlled the heavy anti-aircraft guns. There was one on each side of the forward funnel while the other was atop the rear superstructure. Protection Soviet armor plate plants proved incapable of producing plates of cemented armor thicker than which forced the decision to replace cemented plates thicker than with face-hardened ones with less resistance in November 1940. The plants tended to compensate by making the thicker plates harder, but this often made them more brittle and large numbers did not pass the acceptance tests. This would have significantly reduced the level of protection enjoyed by the Sovetsky Soyuz-class ships in combat. The Sovetsky Soyuz-class ships devoted a total weight of to armor protection, a slightly greater weight than that of the larger Japanese Yamato class (). Their armor was intended to resist 406 mm shells and 500 kg bombs, specifically shells fired from forward bearings between 35° and 50° from the centerline. This led to the very unusual situation where the armor belt thickened toward the bow to compensate for the narrowing of the ship near the forward magazines, which had to be compensated for by thicker armor. The belt was long and covered 57% of the total waterline length. It was inclined 5° to increase its resistance to flat-trajectory shells. Over the machinery spaces it was thick and increased in steps until it was thick over the forward magazines. It was over the rear magazine. The belt armor was carried forward of the magazines at a thickness of and