Nagato's eight 45-caliber 41-centimeter (16 inch) guns were mounted in two pairs of twin-gun, superfiring turrets fore and aft.
Numbered one through 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.
The turrets aboard the Nagato-class ships were replaced in the mid-1930s with the turrets stored from the unfinished Tosa-class battleships.
While in storage the turrets had been modified to increase their range of elevation to –3 to +43 degrees, which increased the gun's maximum range from 30,200 to 37,900 meters (33,000 to 41,400 yd).

The ship's secondary armament of twenty 50-caliber 14-centimeter guns was mounted in casemates on the upper sides of the hull and in the superstructure.
The manually operated guns had a maximum range of 20,500 metres (22,400 yd) and fired at a rate of six to 10 rounds per minute.
Anti-aircraft defense was provided by four 40-caliber 3rd Year Type three-inch AA guns in single mounts.
The 3-inch (76 mm) high-angle guns had a maximum elevation of +75 degrees, and had a rate of fire of 13 to 20 rounds per minute.
The ship was also fitted with eight 53.3-centimeter (21.0 in) torpedo tubes, four on each broadside, two above water and two submerged.

Around 1926, the four above-water torpedo tubes were removed and the ship received three additional 76 mm AA guns that were situated around the base of the foremast.
They were replaced by eight 40-caliber 12.7-centimeter Type 89 dual-purpose (DP) guns in 1932, fitted on both sides of the fore and aft superstructures in four twin-gun mounts.
When firing at surface targets, the guns had a range of 14,700 meters (16,100 yd); they had a maximum ceiling of 9,440 meters (30,970 ft) at their maximum elevation of +90 degrees.
Their maximum rate of fire was 14 rounds a minute, but their sustained rate of fire was around eight rounds per minute.
Two twin-gun mounts for license-built Vickers two-pounder light AA guns were also added to the ship that same year.
These guns had a maximum elevation of +80 degrees which gave them a ceiling of 4,000 meters (13,000 ft).
They had a maximum rate of fire of 200 rounds per minute.

When the ship was reconstructed in 1934–1936, the remaining torpedo tubes and the two forward 14 cm (5-1/2 inch) guns were removed from the hull.
The remaining 14 cm guns had their elevation increased to +35 degrees which increased their range to 20,000 meters (22,000 yd).
An unknown number of license-built Hotchkiss M1929 machine gun 13.2 mm (0.52 in) in twin mounts were added.
The maximum range of these guns was 6,500 meters (7,100 yd), but the effective range against aircraft was 700–1,500 meters (770–1,640 yd).
The cyclic rate was adjustable between 425 and 475 rounds per minute, but the need to change 30-round magazines reduced the effective rate to 250 rounds per minute.

The unsatisfactory two-pounders were replaced in 1939 by twenty license-built Type 96 Hotchkiss Type 96 25 mm (0.98 in) light AA guns in a mixture of twin-gun and single mounts.
This was the standard Japanese light AA gun during World War II, but it suffered from severe design shortcomings that rendered it a largely ineffective weapon.
According to historian Mark Stille, the twin and triple mounts "lacked sufficient speed in train or elevation; the gun sights were unable to handle fast targets; the gun exhibited excessive vibration; the magazine was too small, and, finally, the gun produced excessive muzzle blast".
These 25 mm guns had an effective range of 1,500–3,000 meters (1,600–3,300 yd), and an effective ceiling of 5,500 meters (18,000 ft) at an elevation of 85 degrees.
The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the frequent need to change the fifteen-round magazines.
Additional Type 96 guns were installed during the war; on 10 July 1944, the ship was reported to have 98 guns on board.
An additional 30 guns were added during a refit in Yokosuka in November.
Two more twin 12.7 cm (5 inch) gun mount
Nagato's eight 45-caliber 41-centimeter (16 inch) guns were mounted in two pairs of twin-gun, superfiring turrets fore and aft. Numbered one through 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. The turrets aboard the Nagato-class ships were replaced in the mid-1930s with the turrets stored from the unfinished Tosa-class battleships. While in storage the turrets had been modified to increase their range of elevation to –3 to +43 degrees, which increased the gun's maximum range from 30,200 to 37,900 meters (33,000 to 41,400 yd).
The ship's secondary armament of twenty 50-caliber 14-centimeter guns was mounted in casemates on the upper sides of the hull and in the superstructure. The manually operated guns had a maximum range of 20,500 metres (22,400 yd) and fired at a rate of six to 10 rounds per minute. Anti-aircraft defense was provided by four 40-caliber 3rd Year Type three-inch AA guns in single mounts. The 3-inch (76 mm) high-angle guns had a maximum elevation of +75 degrees, and had a rate of fire of 13 to 20 rounds per minute. The ship was also fitted with eight 53.3-centimeter (21.0 in) torpedo tubes, four on each broadside, two above water and two submerged.
Around 1926, the four above-water torpedo tubes were removed and the ship received three additional 76 mm AA guns that were situated around the base of the foremast. They were replaced by eight 40-caliber 12.7-centimeter Type 89 dual-purpose (DP) guns in 1932, fitted on both sides of the fore and aft superstructures in four twin-gun mounts. When firing at surface targets, the guns had a range of 14,700 meters (16,100 yd); they had a maximum ceiling of 9,440 meters (30,970 ft) at their maximum elevation of +90 degrees. Their maximum rate of fire was 14 rounds a minute, but their sustained rate of fire was around eight rounds per minute. Two twin-gun mounts for license-built Vickers two-pounder light AA guns were also added to the ship that same year. These guns had a maximum elevation of +80 degrees which gave them a ceiling of 4,000 meters (13,000 ft). They had a maximum rate of fire of 200 rounds per minute.
When the ship was reconstructed in 1934–1936, the remaining torpedo tubes and the two forward 14 cm (5-1/2 inch) guns were removed from the hull. The remaining 14 cm guns had their elevation increased to +35 degrees which increased their range to 20,000 meters (22,000 yd). An unknown number of license-built Hotchkiss M1929 machine gun 13.2 mm (0.52 in) in twin mounts were added. The maximum range of these guns was 6,500 meters (7,100 yd), but the effective range against aircraft was 700–1,500 meters (770–1,640 yd). The cyclic rate was adjustable between 425 and 475 rounds per minute, but the need to change 30-round magazines reduced the effective rate to 250 rounds per minute.
The unsatisfactory two-pounders were replaced in 1939 by twenty license-built Type 96 Hotchkiss Type 96 25 mm (0.98 in) light AA guns in a mixture of twin-gun and single mounts. This was the standard Japanese light AA gun during World War II, but it suffered from severe design shortcomings that rendered it a largely ineffective weapon. According to historian Mark Stille, the twin and triple mounts "lacked sufficient speed in train or elevation; the gun sights were unable to handle fast targets; the gun exhibited excessive vibration; the magazine was too small, and, finally, the gun produced excessive muzzle blast". These 25 mm guns had an effective range of 1,500–3,000 meters (1,600–3,300 yd), and an effective ceiling of 5,500 meters (18,000 ft) at an elevation of 85 degrees. The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the frequent need to change the fifteen-round magazines. Additional Type 96 guns were installed during the war; on 10 July 1944, the ship was reported to have 98 guns on board. An additional 30 guns were added during a refit in Yokosuka in November. Two more twin 12.7 cm (5 inch) gun mount
Japanese battleship Nagato