A new design used on France's Treaty Cruisers in twin turrets and 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: John Campbell in his "Naval Weapons of World War Two" published in 1985 states that Algérie was armed with a new gun, the 203 mm/55 (8") Model 1931. Many French and English references both newer and older disagree and state that Algérie used the same 50 caliber gun as did the earlier French 203 mm cruisers. However, John Jordan has recently (December 2024) informed me that he has found what he terms "compelling evidence" that Campbell was correct and that she was indeed armed with a new 55 caliber gun. Mr. Jordan will be formally publishing his findings in "Warship 2026."
| Designation | 203 mm/50 (8") Model 1924 |
|---|---|
| Ship Class Used On | Duquesne, Suffren and Surcouf 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 | Cruisers: 4 - 5 rounds per minute 1 Surcouf: 3 rounds per minute |
- ^Planned rate of fire for cruisers was 5 - 6 rounds per minute, but in practice it was closer to the above values.
| Type | Bag |
|---|---|
| Projectile Types and Weights 1a 2a 3a 4a | SAP M1924 5a 6a: 271.4 lbs. (123.10 kg)
HE M1924: 272.98 lbs. (123.82 kg) |
| Bursting Charge | SAP M1924: 17.8 lbs. (8.07 kg) Mélinite
HE M1924: N/A Mélinite |
| Projectile Length | All: 39.6 in (100.5 cm) |
| Propellant Charge 7a | Original Charge: 116.8 lbs. (53 kg) BM 13 8a Standard Charge: 103.6 lbs. (47 kg) BM 13 |
| Muzzle Velocity 4a | SAP and HE M1924 with Original Charge: 2,936 fps (895 mps)
SAP and HE M1924 with Standard Charge: 2,790 fps (850 mps) |
| Working Pressure 4a | SAP and HE M1924 with Original Charge: 20.3 tons/in2 (3,200 kg/cm2
SAP and HE M1924 with Standard Charge: about 18.0 tons/in2 (2,8000 kg/cm2) |
| Approximate Barrel Life | about 600 rounds |
| Ammunition stowage per gun | Cruisers: 150 rounds 9a Surcouf: 300 rounds |
- ^
Actual French designations SAP M1924 OPf Mle 1924 HE M1924 OEA Mle 1924 - ^As in many French weapons, there were multiple variations of the OPf and OEA projectiles. This was primarily due to which sort of fuze was used in them, such as instantaneous or delay types.
- ^Besides those projectiles listed here, these cruisers were also issued projectiles developed later for the 203 mm/55 (8") Model 1931 guns. Please see that datapage for details.
- ^4.14.24.3In the mid-1930s the heavier APC 1936 was introduced. See the 203 mm/55 (8") Model 1931 datapage for details. The muzzle velocity for this projectile with the Later Charge in the M1924 gun was about 2,690 fps (820 mps) and the working pressure was about 19.0 tons/in2 (3,000 kg/cm2).
- ^Research by myself and John Jordan suggests that the SAP M1924 did not have an armor cap.
- ^Some of these and the later shell types had a dye bag added after March 1939. Colors were assigned as follows:
Ship Color Duquesne red Tourville yellow Suffren green Others N/A - ^The propellant charge was in halves. Each cartridge used a 1.76 lbs. (0.80 kg) black powder igniter.
- ^The Original Charge was found to cause excessive bore erosion and was replaced with the Standard Charge to reduce the muzzle velocity.
- ^At least the Suffren class and probably the others had a peacetime outfit of 120 rounds per gun but had enough magazine space for 150 rounds per gun.
| Elevation | SAP and HE @ MV = 2,790 fps (850 mps) [Standard Charge] | APC M1936 @ MV = 2,690 fps (820 mps) [Later Charge] |
|---|---|---|
| 30 degrees | 30,620 yards (28,000 m) | --- |
| 45 degrees | 34,340 yards (31,400 m) | about 32,800 yards (30,000 m) |
The range for the SAP and HE when using the Original charge [MV of 3,936 fps (895 mps)] is not known.
| Designation | Cruiser Two-gun Turret 1b Duquesne (4) and Suffren (4): Model 1924 2b Algérie (4): Model 1931 Submarine Twin Mounting
|
|---|---|
| Weight 4b | Model 1924: 177 tons (180 mt)
Model 1929: N/A |
| Elevation | Model 1924: -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 1929: about +90 / -90 degrees |
| Train Rate | Model 1924: 6 degrees per second Model 1929: N/A |
| Gun recoil | 27.5 in (70 cm) |
| Loading Angle | -5 / +10 degrees |
- ^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. RPC for training was added during the 1930s. The Model 1924 was considered successful and was used on all cruisers except Algérie. Her M1931 turrets were similar to the previous M1924 but had more powerful training motors to handle the increased armor weight.
- ^Model 1924 gun axes were 74 in (188 cm) apart while those in Model 1929 were about 104 in (264 cm) apart.
- ^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.
- ^Armor thickness of the Model 1924 turrets from "French Cruisers: 1922 - 1956" 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.
"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
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Ministère de la défense
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Special help from Zhu Shipeng and Email conversations with John Jordan of 14 February 2022 and 10-17 December 2024
22 July 2007 - Benchmark
03 March 2012 - Updated to latest template
28 March 2013 - Added photographs of Foch and Algérie
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. Redid side view photograph of Surcouf and added new photograph of Surcouf showing the turret training.
11 November 2020 - Updated to HTML 5 format
12 March 2022 - Added sketch of 203 mm SAP projectile, added details to ammunition table
17 August 2022 - Added ammunition RPG for cruisers, added details to turret design
13 May 2023 - Added additional details in note for SAP M1927
04 August 2024 - Added sketches of OPf(k) 1936 ammunition
17 December 2024 - Redid ammunition section based upon new research