"Mutsu"s eight 45-calibre 41 cm/45 3rd Year Type naval gun guns were mounted in two pairs of twin-gun, superfiring turrets fore and aft. Numbered one to four from front to rear, the hydraulically powered turrets gave the guns an elevation range of −2 to +35 degrees. The rate of fire for the guns was around two rounds per minute. A special Type 3 "Sankaidan" incendiary shrapnel shell was developed in the 1930s for anti-aircraft use. The turrets aboard the "Nagato"-class ships were replaced in the mid-1930s using those stored from the unfinished s. While in storage the turrets were modified to increase their range of elevation to −3 degrees to +43 degrees, which increased the guns' maximum range from .