France
203 mm/50 (8") Model 1924
Updated 08 January 2016

A new design used on France's Treaty Cruisers in twin turrets.  Also used in a special lightweight twin mounting on the submarine Surcouf.

This weapon was of simple construction with a thick autofretted A tube, shrunk jacket and breech ring.  The Welin breech-block opened upwards.

Actual bore diameter was 20.30 cm (7.992").

A note on sources:  Many references state that Algérie used a longer 55 caliber gun, but recent research by John Jordan and Jean Moulin in their "French Cruisers:  1922 - 1956" has determined that she carried the same 50 caliber guns as did the older cruisers.

WNFR_8-50_m1924_Dupleix_pic.jpg

Heavy Cruiser Dupleix in 1940
Ministère de la Défense Photograph

.
Click here for additional pictures
.
.
Gun Characteristics
.
Designation 203 mm/50 (8") Model 1924
Ship Class Used On Duquesne, Suffren, Surcouf and Algérie classes
Date Of Design 1924
Date In Service 1928
Gun Weight 20.389 tons (20.716 mt) including BM
Gun Length oa 413.4 in (10.5 m)
Bore Length 399.6 in (10.150 m)
Rifling Length 319.8 in (8.122 m)
Grooves (60) 0.75 in deep x 0.295 in (1.9 mm x 7.5 mm)
Lands 0.118 in (3.0 mm)
Twist Uniform RH 1 in 25.59
Chamber Volume 5,595 in3 (91.682 dm3)
Rate Of Fire
(see Note)
Cruisers:  4 - 5 rounds per minute

Surcouf:  3 rounds per minute

Note:  Planned rate of fire for cruisers was 5 - 6 rounds per minute, but in practice it was closer to the above values.
.
Ammunition
.
Type Bag
Projectile Types and Weights
(see Note 1)
APC M1927 - 271.4 lbs. (123.1 kg)
APC M19?? - 262.5 lbs. (119.07 kg)
APC M1936 - 295 lbs. (134 kg)

HE M1927 - 273.0 lbs. (123.82 kg)
HE M19?? - 263.9 lbs. (119.72 kg)

Bursting Charge APC M1927 - 17.8 lbs. (8.07 kg) Mélinite
HE - about 18.2 lbs. (8.3 kg)
Others - N/A
Projectile Length APC M1936 - 38.2 in (97 cm)
Others - 39.6 in (100.5 cm)
Propellant Charge For APC M1936 - 103.6 lbs. (47 kg) BM 13
Others - 116.8 lbs. (53 kg)
Muzzle Velocity APC M1936 - 2,690 fps (820 mps)
Others - 2,789 fps (850 mps)
Working Pressure APC M1936 - about 19.0 tons/in2 (3,000 kg/cm2)
APC - 20.3 tons/in2 (3,200 kg/cm2)
Approximate Barrel Life about 600 rounds
Ammunition stowage per gun Surcouf:  300 rounds
Others:  N/A
Notes:

1) Actual projectile designations:
       APC M1927 - Opf Mle 1927
       APC M19?? - Opf Mle 19??
       APC M1936 - Opf Mle 1936
       HE M1927 - OEA Mle 1927
       HE M19?? - OEA Mle 19??

2) APC M1936 added a dye bag in 1939. Colors were assigned as follows:
       Duquesne - red
       Tourville - yellow
       Suffren - green
       Others - N/A

3) The propellant charge was in halves.

.
Range
.
Elevation With 271.4 lbs. (123.1 kg) APC M1927 Shells
Range @ 45 degrees 34,340 yards (31,400 m)
Range @ 30 degrees 30,620 yards (28,000 m)
Elevation With 295 lbs. (134 kg) APC M1936 Shells
Range @ 45 degrees about 32,800 yards (30,000 m)
Elevation With 295 lbs. (134 kg) HE M1927 Shells
Range @ 45 degrees about 32,800 yards (30,000 m)
.
Mount / Turret Data
.
Designation
(see Note 5)
Cruiser Two-gun Turret
   Duquesne (4) and Suffren (4):  Model 1924
   Algérie (4):  Model 1931

Cruiser Three-gun Turret
  C5 and St. Louis (3):  N/A

Submarine Twin Mounting
   Surcouf (1):  Model 1929

Weight Model 1924:  177 tons (180 mt)

Model 1931:  about 220 tons (240 mt)

Model 1929:  N/A

Elevation Model 1924 and Model 1931:  -5 / +45 degrees

Model 1929:  -5 / +30 degrees

Elevation Rate Model 1924:  about 10 degrees per second

Model 1929:  N/A

Train Model 1924 and Model 1931:  about +150 / -150 degrees

Model 1929:  about +90 / -90 degrees

Train Rate Model 1924 and Model 1931:  6 degrees per second

Model 1929:  N/A

Gun recoil 27.5 in (70 cm)
Loading Angle -5 / +10 degrees
Notes:

1) The cruiser mountings used catapult rammers cocked by the recoil forces to load projectiles while propellant charges were loaded by hand.  Guns were individually sleeved.  Each gun used a 30 hp elevating electric motor and the guns could be coupled together.  Turrets used a 22.5 hp electric training motor with hydraulic drive and were equipped for RPC for training during the mid-1930s refits.  However, RPC for elevation was not added.  Shell rooms were generally below the magazines, except for some bow mountings which were on the same level.  Dredger hoists from the magazines ran up to a working chamber where ammunition was transferred to the upper cage hoists which each carried a projectile and two half charges.  Upper hoists ended on the outside of the guns and the projectiles were transferred by swinging arms which were locked to the guns for loading.

2) The Model 1929 used on the submarine Surcouf could open fire within 2.5 minutes after she surfaced.  Guns were not individually sleeved and the turret was water-tight.

3) Model 1924 gun axes were 74 in (188 cm) apart while those in Model 1929 were about 104 in (264 cm) apart.

4) The weight differences for the cruiser turrets were mainly due to armor thickness, which "French Cruisers:  1922 - 1956" list as follows:

Model 1924 - Duquesne and Suffren classes
   Front - 1.2 in (3 cm)
   Sides - 1.2 in (3 cm)
   Roof - 1.2 in (3 cm)
   Rear - 1.2 in (3 cm)

This protection was provided by riveting two 0.6 in (1.5 cm) HT plates together.

Model 1931 - Algérie
   Front - 3.9 in (10 cm)
   Sides - 2.8 in (7 cm)
   Roof - 2.8 in (7 cm)
   Rear - 1.96 - 3.3 in (5 - 8.5 cm)
   Floor - 1.6 in (4 cm)

5) In 1939 the French started designing new cruisers that were intended to replace the Duguay-Trouin class.  The preliminary design was known as "C5" and was for a 10,000 ton Treaty Cruiser similar to Algérie but having nine 203 mm (8") guns in three turrets.  The start of the war ended all treaty restrictions and in early 1940 a more ambitious nine-gun design known as "St. Louis" was under consideration.  Little more than some preliminary sketches for a ship of around 15,000 tons were completed before the June 1940 Armistice halted all work.

.
Data from
"Warship Volume VII" article by Francis J. Allen
"Naval Weapons of World War Two" by John Campbell
"French Cruisers:  1922 - 1956" by John Jordan and Jean Moulin
"Navies of the Second World War - The French Navy" by Henri le Masson
"Cruisers of World War Two" by M.J. Whitley
---
Ministère de la défense
Page History

22 July 2007 - Benchmark
03 March 2012 - Updated to latest template
06 April 2013 - Added projectile and mounting information, notes on Algérie and note on 1939-1940 designs
08 January 2016 - Corrected training angles for Surcouf