1) Firing cycle was 21.5 seconds at low elevations, which probably means at the loading angle of +3 degrees.

2) US Naval Technical Mission to Japan report O-54(N) states that guns meant to be loaded at high elevations had "ridges around the compression slope, to aid in gripping the projectile rotating bands and prevent the projectile from slipping back after seating."

3) The post-war US survey of Japanese Seacoast Artillery states that the coastal artillery turrets could fire 1 round per gun per minute.

World War II
   APC Type 91 - 2,249 lbs. (1,020 kg)
   Common Type 0 HE - 2,069 lbs. (938.5 kg)
   Common Type 3 IS - 2,072 lbs. (940 kg)
   Illum - N/A

Others - N/A

Others - N/A

World War II:  483 lbs. (219 kg) 102 DC₁ or 110 C₂

APC Type 91 - 2,645 fps (806 mps) [new gun]
APC Type 91 - 2,559 fps (780 mps) [average gun]
Common Type 0 HE - 2,641 fps (805 mps)
Common Type 3 IS - 2,641 fps (805 mps)
Illum - 2,297 fps (700 mps)

1) IS is my abbreviation for the incendiary shrapnel round (sankaidan) intended for AA use.  Fuzes were usually set on the waiting tray in the working chamber.

2) The APC Type 3 was adopted in 1917.  This was superseded by the APC Type 5 which was adopted on 15 June 1925 and was in turn superseded by the APC No. 6 which was adopted on 17 November 1928.  APC No. 6 was essentially similar to the Type 5 in terms of armor penetration but was better protected from premature detonation and had enhanced underwater performance.  APC No. 6 was redesignated as the Type 88 on 6 April 1931.  On that same date, the improved APC Type 91 was adopted.  By World War II, APC Type 5 was only used by the coastal artillery units.  Dye was introduced in 1941 and Type 91 shells containing it were designated as Type 1.

3) Type 91 shells were all 6 / [infinity] crh with boat tail and two copper driving bands.  The diameter of the bourrelet was 16.11 in (40.919 cm).  AP Cap, cap head and windshield together weighed 358 lbs. (162.4 kg).

4) The propellant charge was in four bags.  Bags had a single 8.8 oz (250 gm) black powder igniter patch.

5) The Shômeidan B₁ Illumination round had an illuminating power of 5.3 million candelas.  The maximum ballistic range was 24,900 yards (22,770 m).

1) These bombs were rated as being able to penetrate 5.9 inches (15 cm) of armor plate.  Height for this performance is not available but was probably around 10,000 feet (3,000 m).

2) An aluminum plug was used between the burster and the cap as a shock absorber.

3) Both types had two base fuzes to ensure detonation.

Nagato class as modernized:  -3 / +43 degrees

Coastal Defense turrets:  -2 / +35 degrees

1) The turrets intended for the canceled ships had improved protection and were somewhat larger and roomier than the earlier ones used on the Nagato class.  For that reason, when the Nagato class were modernized during the mid-1930s, they were then given turrets taken from the unfinished battleships Kaga and Tosa.  The elevation of these later mountings was increased by deepening the gun wells and lowering the revolving structure further down into the ships.  The original Nagato class turrets had sighting hoods on the roof of the turrets while the later ones had sighting ports on the sides of the turrets.  This is consistent with British practice where their post-Jutland designs did away with hoods in favor of ports. The close relationship between the British and Japanese navies meant that the Japanese designers were well aware of this changeover and incorporated this knowledge into improving their own designs.

2) The design of this mounting was very similar to that for the British 15"/42 (38 cm) Mark I.  For example, like the British gun, the rammers were mounted on a continuation of the slide and could ram at any angle of elevation.  Difficulties with this method, probably similar to those found by the British, led to the rebuilt mountings having a fixed loading angle of +3 degrees.  The mountings were powered from a hydraulic ring main.  The training gear used a worm drive which was subject to wear problems.  A double longitudinal bulkhead separated the two guns and also the working chamber.  This consisted of two flashtight bulkheads spaced about 20 inches (50 cm) apart.  A flashtight door in this bulkhead was the only access between the two sides of the turret.  The working chamber where shells and charges were transferred from lower to upper hoists was similarly subdivided.  Shell rooms were above the magazines.  The post-war US survey of Japanese Seacoast Artillery states that the coastal artillery turrets could be theoretically loaded at any angle up to +15 degrees but actually the loading angle could not exceed +5 degrees.

3) The US Naval Technical Mission to Japan report O-47(N)-1 states that "Japanese major caliber turrets (14 and 16-inch) are all of old design and were copied from the British-built turrets for the BB Kongo.  In general arrangement and in most details, they are similar to the British 15-inch turrets, but some improvements have been made by the Japanese . . .[including] Better flash tightness in gunhouses and working chambers.  All battleships were fitted with longitudinal flashtight bulkheads between the guns, and between the gun loading hoists in the working chambers. . . In the 16-inch turrets, the gunloading cages are designed to hold four one-quarter charges end to end, thus enabling a full charge to be rammed with a single stroke of the rammer."

4) Run out was by compressed air.  Gun elevation was by cylinder and piston attached to the rear of the slide.  Each gun loaded from a cage which contained the shell and all four charges laid end to end in a flash tight compartment.  This allowed the charges to be rammed in a single stroke.

5) The gun axes were 96 in (244 cm) apart.

6) The coast defense mountings are thought to be those originally intended for either Kaga or Tosa.  These turrets were more rectangular in appearance and were powered by individual oil hydraulic units rather than by a ring main as in the earlier turrets.  A post-war USN report states that the Tsushima battery lacked adequate fire control and communications equipment.

7) Armor thickness of original turrets given in "Nagato Details" by Sander Kindsepp:
    Face:  11.7 in (29.9 cm)
    Sides:  8.8 in (22.4 cm)
    Rear:  7.4 in (18.7 cm)
    Roof:  4.9 - 5.9 in (12.5 - 14.9 cm)
    Floor:  3.9 in (10.0 cm)

Armor thickness of modernized turrets given in "Naval Weapons of World War Two" by John Campbell:
    Face:  18.1 in (46.0 cm)
    Sides:  11.0 in (28.0 cm)
    Rear:  7.5 in (19.0 cm)
    Roof:  9.8 - 9.0 in (25.0 - 23.0 cm)

Coastal Defense Turrets given in "Survey of Japanese Seacoast Artillery, 1946" by US Army:
    Face:  12.0 in (30.5 cm)
    Sides:  12.0 in (30.5 cm)
    Roof:  4.0 in (10.2 cm)

Modernized turrets were given thicker armor plating during the 1930s rebuilds.