Japan
41 cm/45 (16.1") 3rd Year Type
40 cm/45 (16.1") 3rd Year Type
Updated 16 July 2014

These were the first large-caliber guns designed entirely in Japan.  They were mounted afloat only on the Nagato class, but had been planned for use on the Kaga, Amagi and Kii classes of the early 1920s, all of which were canceled as a result of the Washington Naval Limitation Treaty.  Those completed guns and mountings intended for the canceled ships were then used for the modernization of the Nagato class during their 1930s rebuilds and as coastal artillery, covering the southern entrance to the Sea of Japan.  One of the old turrets removed from Mutsu was installed as a static display at the Japanese Naval Academy at Etajima.

These guns were generally similar to British wire wound guns of the time but were of lighter construction, being about an inch (25 mm) less in diameter at the muzzle than the 15"/42 (38 cm) Mark I.  This may indicate that they were not wire wound over their full length.  Used a Welin screw breech but with an Elswick 3-motion short-arm mechanism, which resembled that used on the British 18"/40 (46 cm) guns of 1917.  The breech block needed to be withdrawn straight back into the carrier before it could be swung.  A total of about 40 guns were manufactured at the Kure and Muroran Ironworks.

Mutsu was destroyed by a main magazine explosion on 8 June 1943.  The Japanese attempted to salvage the wreck both during and shortly after the war but it was not until 1970 that a successful effort was begun.  Two guns recovered from Turret #3 are now displayed at the Yamato Museum in Kure and at the Museum of Maritime Science in Tokyo.

Originally designated as 41 cm/45 3rd Year Type.  Redesignated as 40 cm/45 3rd Year Type on 29 March 1922.  Actual bore diameter was 41.0 cm (16.14 inch).

Some of the APC shells for these guns were converted into aircraft bombs and then designated as Type 99 (Model 1939) No 80 Mark 5.  It is believed that one of these destroyed USS Arizona BB-39.  In 1942 the design was modified and new bombs were then designated as Type 2 (Model 1942) No 80 Mark 5 Model 1.

WNJAP_161-45_3ns_Nagato_bow_pic.jpg

Bow Turrets of Battleship Nagato

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Click here for additional photographs
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Gun Characteristics
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Designation 41 cm/45 (16.1") 3rd Year Type (Model 1914)
40 cm/45 (16.1") 3rd Year Type (Model 1914)
Ship Class Used On Nagato, Kaga, Amagi and Kii Classes
Date Of Design 1914
Date In Service 1921
Gun Weight 100 tons (101.6 mt)
Gun Length oa 741.7 in (18.840 m)
Bore Length 720.24 in (18.394 m)
Rifling Length 615.3 in (15.629 m)
Number Of Grooves (84) 0.161 in deep x 0.345 in (4.1 mm x 8.754 mm)
Lands 0.259 in (6.58 mm)
Twist Uniform RH 1 in 28
Chamber Volume 28,505 in3 (467.11 dm3)
Rate Of Fire 1.5 - 2.5 rounds per minute
Notes:

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.

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Ammunition
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Type Bag
Projectile Types and Weights
(see Notes 1 and 2)
Prior to World War II
   APC Type 3 - N/A, but probably 2,205 lbs. (1,000 kg)
   APC Type 5 - 2,205 lbs. (1,000 kg)
   APC No. 6 / Type 88 - 2,205 lbs. (1,000 kg)

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

Bursting Charge APC Type 91 - 32.8 lbs. (14.89 kg)
Common Type 0 HE - 97.7 lbs. (44.3 kg)

Others - N/A

Projectile Length APC Type 91 - 68.4 in (173.85 cm)
Common Type 0 HE - 55.1 in (140 cm)
Common Type 3 IS - 70 in (160 cm)

Others - N/A

Propellant Charge World War I:  494 lbs. (224 kg)

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

Muzzle Velocity APC Type 3 - N/A, but probably 2,592 fps (790 mps)
APC Type 5 - 2,592 fps (790 mps)
APC Type 6 / Type 88 - 2,592 fps (790 mps)

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)

Working Pressure 19 - 19.5 tons/in2 (3,000 - 3,070 kg/cm2)
Approximate Barrel Life 250 - 300 rounds
Ammunition stowage per gun About 90 rounds
Notes:

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 redesignated 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).

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Range
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Elevation
With 2,249 lbs. (1,020 kg) APC
Striking Velocity
Angle of Fall
2.5 degrees
5,470 yards (5,000 m)
2,247 fps (685 mps)
3.4
5.7 degrees
10,940 yards (10,000 m)
2,001 fps (610 mps)
7.5
9.2 degrees
16,400 yards (15,000 m)
1,768 fps (539 mps)
11.8
13.5 degrees
21,870 yards (20,000 m)
1,624 fps (495 mps)
17.5
18.8 degrees
27,340 yards (25,000 m)
1,526 fps (465 mps)
24.5
25.5 degrees
32,810 yards (30,000 m)
1,516 fps (462 mps)
34.0
43.0 degrees 
(max elevation
of turret)
42,350 yards (38,725 m)
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Elevation With 2,069 lbs. (938.5 kg) HE
Range @ 43.0 degrees 33,930 yards (31,025 m)
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Aircraft Bombs
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Characteristic
Type 99 (Model 1939) No 80 Mark 5
Type 2 (Model 1942) No 80 Mark 5 Model 1
Bursting Charge
49.4 lbs. (22.4 kg) TNA
78.7 lbs. (35.7 kg) TNA
Total Weight
1,757 lbs. (796.8 kg)
1,788 lbs. (811.2 kg)
Length oa
92.6 in (235.1 cm)
91.7 in (233.0 cm)
Diameter
16.1 in (40.9 cm)
15.9 in (40.4 cm)
Nose thickness
19.17 in (48.7 cm)
11.97 in (30.4 cm)
Notes:

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.

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Mount / Turret Data
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Designation Two-gun Turrets
   Original Design:  Nagato (4)
   New Design:  Kaga (5), Amagi (5) and Kii (5)
Weight 1,004 tons (1,020 mt)
Elevation
(see Note 2)
Original Design:  -5 / +30 degrees

New Design:  -3 / +35 degrees

Nagato class as modernized:  -3 / +43 degrees

Coastal Defense turrets:  -2 / +35 degrees

Rate of Elevation 5 degrees per second
Train about +/- 130 degrees
Rate of Train 3 degrees per second
Gun Recoil N/A
Loading Angle
(see Note 1)
Original:  -5 to +20 degrees
As rebuilt:  +3 degrees
Notes:

1) The design of the original 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 theoretically ram at any angle of elevation.  Difficulties with this method, probably similar to those found by the British, led to the newer mountings intended for the canceled ships having a fixed loading angle of +3 degrees.  Mountings were powered from a hydraulic ring main.  The training gear used a worm drive which was subject to wear problems.  Shell rooms were above the magazines.  When these turrets were removed during the 1930s rebuilds, Turret #4 from Mutsu was erected as a static display at the Naval Academy on Etajima.  It is not clear what happened to the other seven turrets, but they appear to have been scrapped.

2) 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.  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 was 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.  During the modernization of the Nagato class during the mid-1930s, their original eight turrets were removed and these ships were then rearmed with eight of the turrets originally intended for Kaga and Tosa.  The maximum elevation of these later mountings was also increased to +43 degrees during the rebuilds by deepening the gun wells and lowering the revolving structure further down into the ships.  The armor thickness on these turrets was also increased as noted below.  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.

3) The contracts for the turrets intended for the canceled ships were split between the Kure Arsenal and the Yokosuka Arsenal.  The Kure Arsenal was contracted to build five mountings for Amagi, three for Akagi, three for Tosa and five for Kaga.  The Yokosuka Arsenal was contracted to build two mountings for Akagi and two for Tosa.  No orders were placed for the Kii class turrets prior to their cancellation in 1922.  Out of the twenty turrets contracted, it appears that a total of fourteen were actually completed, with eight of these being used to rearm the Nagato class during mid-1930s modernization program.  The remaining six were transferred to the Army.  Four of these were modified with three being actually emplaced to guard the southern entrance of the Sea of Japan and the fourth held as a spare.  The other two were not modified and were also held in reserve.  The coast defense turrets were powered by individual oil hydraulic units rather than by a ring main as in the earlier turrets.  The turret emplaced at the Toyo Battery on Tushima was originally Tosa Turret #1; the Choshito Battery at Busan, Korea was Tosa Turret #2; and the Kurosaki Battery on Ikishima was Akagi Turret #1.  The US Naval Technical Mission to Japan report O-55(N) states that the Tsushima battery lacked adequate fire control and communications equipment.  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 in actuality the loading angle could not exceed +5 degrees.

4) 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."

5) 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.

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

7) Armor thickness of original turrets as 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 Coastal Defense Turrets as given in "Survey of Japanese Seacoast Artillery, 1946" by US Army (this was probably the armor protection intended for the canceled ships):
    Face:  12.0 in (30.5 cm)
    Sides:  12.0 in (30.5 cm)
    Roof:  4.0 in (10.2 cm)

Armor thickness of new turrets used to rearm the Nagato class as 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)

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Data from
"Naval Weapons of World War Two" by John Campbell
"Battleships:  Axis and Neutral Battleships in World War II" by W.H. Garzke, Jr. and R.O. Dulin, Jr.
"The Japanese Ships of the Pacific War" by The Koku-Fan
"Japanese Cruisers of the Pacific War" by Eric Lacroix and Linton Wells II
"Ship's Data IJN Warships 1868-1945 - Part 1 Battleships and Battlecruisers" by Ishibashi Takao
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US Naval Technical Mission to Japan report O-19:  Japanese Projectiles General Types
US Naval Technical Mission to Japan report O-47(N)-1:  Japanese Naval Guns and Mounts-Article 1, Mounts Under 18"
US Naval Technical Mission to Japan report O-55(N):  "Defenses of Tsushima and Entrance to Sea of Japan"
US Army Report "Survey of Japanese Seacoast Artillery, 1946"
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"Nagato Details" an unpublished paper by Sander Kindsepp
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Special help from Rob Lundgren and J. Bren
Page History

19 April 2007 - Benchmark
11 May 2009 - Fixed typographical error
30 June 2012 - Added information about surviving guns, turret designs, armor thickness, use as coastal artillery and flashtightness of turrets
16 July 2014 - Added additional information about turrets intended for cancelled ships