The building of Britain's "Super-Dreadnoughts" prompted France to increase the size of her battleship guns as well. This meant a reduction from twelve main guns to ten, but this was more than offset by the abandonment of wing turrets in favor of having all turrets on the centerline.

The Model 1921 was the original design and were used on the Bretagne class. These guns were considered to be an excellent weapon by the French, but the ships they were installed on were handicapped by poor fire control and low maximum turret elevations and hence a short range. Salvo dispersions at their maximum range of 15,860 yards (14,500 m) was 330 feet (100 m).

The Model 1912M was a slightly modified version intended to be used on the Normandie class which were never completed. Some of the unused guns intended for these ships were used as railway guns while others were later used to rearm the Bretagne class when they were reconstructed in the 1930s. Other spare guns were employed as coast artillery, with four guns in two twin turrets being mounted at Cap Cépet near Toulon. Four additional guns were used with a French version of the German BSG mounting and installed at Plouharnel near Quiberon. After Provence was scuttled at Toulon in November 1942, the Germans removed two guns from her after turrets and used them in Turret F at Cap Cépet to replace two guns that had been sabotaged by the French. These emplacements saw action in August 1944 during the Allied invasion where they were fired upon by the French battleship Lorraine and by USS Nevada (BB-36).

The Type C, an interim designation, was planned for the never-built Lyon class. This would have used the same barrel as the Model 1912M but designed to fire an improved and lengthened APC projectile. No guns were built and a Model Year designation was never assigned.

In May 1943 the French proposed to the USA that the incomplete Jean Bart be finished in a US yard as a combination anti-aircraft / carrier platform. Jean Bart had already given up her four operational 380 mm (14.96") guns to re-arm sister-ship Richelieu, so this proposal saw refitting Jean Bart's single main turret with four 34 cm (13.4") guns taken from the old battleship Lorraine together with cradles from the Métline coastal defense battery in Tunisia. All smaller caliber guns were to be removed and replaced with fifteen twin 5"/38 (12.7 cm) mountings and sixteen 40 mm Bofors quad mountings. Six aircraft of either USA Avenger or British Barracuda torpedo bomber types along with US Hellcat or British Seafire fighters were to be carried. A second proposed reconstruction saw removal of all aircraft facilities and the secondary battery increased to seventeen twin 5"/38 (12.7 cm) mountings along with twenty 40 mm quads. This latter design also entailed using eight Mark 37 GFCS and twenty Mark 51 fire control systems. Nothing came of this plan as the USN decided that their resources would be much better spent turning out new ships rather than to use them to rearm an obsolescent foreign warship - the guns and directors were the equivalent of about six Gearing class destroyers. Following this decision, Jean Bart then languished until her postwar rebuild in France.

Gun construction was generally similar to that of the 380 mm (14.96") guns used on the later Richelieu class battleships, but there was an additional C tube and no loose liner. The Welin breech block is believed to have opened horizontally.

French guns designed between about 1902 and 1922 were designated in centimeters. Actual bore length was 45.82 calibers.

Designation	34 cm/45 (13.4") Model 1912 34 cm/45 (13.4") Model 1912M 34 cm/45 (13.4") Type C
Ship Class Used On	Model 1912: Bretagne class Model 1912M: Normandie 1 Type C: Lyon classes
Date Of Design	1912
Date In Service	1915
Gun Weight	65.89 tons (66.95 mt)
Gun Length oa	634.5 in (16.115 m)
Bore Length	609.6 in (15.485 m)
Rifling Length	521.7 in (13.250 m)
Grooves	(102) 0.075 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 29.89
Chamber Volume	15,646 in3 (256.4 dm3)
Rate Of Fire	about 2 rounds per minute 2

• ^During rebuilds in the 1930s, guns originally intended for the uncompleted Normandie class were used to regun the Bretagne class.
• ^The firing cycle was officially listed at 28 seconds but in practice the ships could fire one round every 35 seconds. In case of hoist failures, the auxiliary hoist could be manually worked by eight men to bring up one complete round every seven minutes. It then took a second crew of four men five minutes to hoist the round into the gunhouse.

Type	Bag
Projectile Types and Weights 1a 2a 3a	Ship Projectiles    APC M1912 4a: 1,190 lbs. (540 kg)    APC M1912-1921 5a 6a: 1,221 lbs. (554 kg)    HE M1926: 842 lbs. (382 kg) Projectiles for Railway Guns    HE 15A: 1,025 lbs. (465 kg)    HE17 FATO: 981 lbs. (445 kg)    HE FATO 32-6: 952 lbs. (431.8 kg) Projectile for Coast Defense Guns    APC M1924 7a: 1,268 lbs. (575 kg)
Bursting Charge	APC M1912-1921: 47.8 lbs. (21.7 kg) Others: N/A
Projectile Length	APC M1912: 42.1 in (107.0 cm) APC M1912-1921 5a: 49.6 in (126.0 cm) APC M1924: about 58.9 in (150.0 cm) HE M1926: 41.5 in (105.4 cm) Others: N/A
Propellant Charge 8a	APC M1912: 341.7 lbs. (155.0 kg) BM 17 APC M1912-1921: 341.7 lbs. (155.0 kg) BM 1 APC M1924: 338.4 lbs. (153.5 kg) BM 16 HE M1926: 308.6 lbs. (140 kg) BM 15 HE 15A: 338.4 lbs. (153.5 kg) BM 16 HE 17 FATO: 390 lbs. (177 kg) SD19G HE FATO 32-6: 390 lbs. (177 kg) SD19G
Muzzle Velocity	APC M1912: 2,605 fps (794 mps) APC M1912-1921: 2,559 fps (780 mps) HE M1926: 2,904 fps (885 mps) HE 15A: 2,930 fps (893 mps) HE 17 FATO: 3,005 fps (916 mps) HE FATO 32-6: 3,022 fps (921 mps)
Working Pressure	17.8 tons/in2 (2,800 kg/cm2)
Approximate Barrel Life	about 250 rounds
Ammunition stowage per gun	Bretagne: 100 rounds Normandie: 100 rounds Lyon: N/A, but probably 100 rounds

• ^A Note on Sources: The secondary sources listed below differ greatly on the details for the ammunition used for these guns. John Jordan kindly provided me with information taken from French official documents and these values are used throughout this section for shipboard projectiles.
• ^Of the projectiles listed here, only the first three were used on ships, the others were used only for Railway and Coastal Defense guns.
• ^

  Actual designations for Ship Projectiles

  APC M1912	340 mm OPf Mle l912
  APC M1912-1921	340 mm OPf Mle 1912-1921
  HE M1926	OEA Mle 1926

• ^The APC M1912 did not have a ballistic cap. They were classified as obus alourdi (heavyweight shell). The base fuzes had a dual delay mechanism which in theory enabled them to engage both thin-skinned and heavily armored targets. They therefore replaced both the separate APC (obus de rupture) and SAPC (obus de semi-rupture) shells carried by earlier battleships. These dual delay base fuzes did not work particularly well but their performance was improved over the years.
• ^5.15.2The APC M1912-1921 had a detachable ballistic cap and was designed to be stable during an underwater trajectory.
• ^The APC M1912-1921 was modified to add dye bags around 1940 (K version). These projectiles weighed 1,230 lbs. (558 kg) and were 49.6 inches (126.0 cm) long.
• ^It is not known if any ships were modified to use the significantly longer APC M1924.
• ^Propellant was in four bags.
• The new APC intended for the Type C guns would have weighed 1,300 lbs. (590 kg) with a burster of 47.6 lbs. (21.6 kg) and a length of 51.2 in (130 cm). It was designed to have an underwater trajectory up to (100 m). This design eventually became the post-war APC M1912-1921.

• The "Warship Volume X" articles listed below give contradictory ranges for 18 degrees of elevation. The above tables attempt to reconcile the data in those articles and also contain information provided by John Jordan.
• The APC Model 1912 had a residual velocity of 1,552 fps (473 mps) at the designed engagement range of 10,940 yards (10,000 m).

Designation	Twin Turret: Bretagne (5) 1c 2c 3c Quad Turret: Normandie (3) and Lyon (4) 4c
Weight	Twin Turrets: About 985 tons (1,000 mt) Quad Turrets: About 1,476 tons (1,500 mt)
Elevation	Bretagne: -5 / +12 degrees 5c Normandie and Lyon: -5 / +15 degrees 6c Coastal Artillery: 0 / +50 degrees
Rate of Elevation	Twin Turret: 3.0 degrees per second 7c Quad Turret: 3.0 degrees per second
Train	Forward and aft turrets: about -150 / +150 degrees Q turret: about 30 to 150 degrees on either side
Rate of Train	Twin Turret: 4.5 degrees per second 8c Quad Turret: 4.5 degrees per second 9c
Gun Recoil	N/A
Loading Angle	+2 degrees

• ^The twin turrets were similar to the 30 cm turrets used on the Courbet class. They used British-style split hoists and ammunition transfers in the working chamber. The main hoist was divided into three sections by flash-tight automatic doors, but the magazine doors had to be left open during action as there was no flash-tight doors or scuttles through which charges could be passed. The upper cage hoist was also fitted with flame-proof shutters. Eight projectiles were stored in the working chamber and these could be lifted to the gunhouse by a small crane should upper hoists fail.
• ^The amidships turret was removed from Lorraine in 1934-35 in order to fit an aircraft catapult and additional AA guns.
• ^Turret No. 2 on the Bretagne class was fitted with an 8.20 m (26 ft) rangefinder during various rebuilds in the late 1920s and early 1930s.
• ^The quad turrets had four guns arranged in two pairs with a 1.6" (4 cm) longitudinal bulkhead separating the pairs. Turrets were trained electrically but elevated hydraulically by Williams-Janney motors for control. These turrets differed from previous ones by having a separate compartment at the base of the forward end of the turret which housed the turret commander, rangetaker and telephone operator. The mounting also differed from earlier ones by having the magazines and shell rooms concentric with the stalk with the magazines above the shell rooms. Two dredger hoists, one for each pair of guns, ran from here up to the working chamber. The hoists were linked such that one would be descending while the other was ascending. Cages had three levels, similar to earlier ships, with the projectile on the lowest level. When the cage arrived at the working chamber the projectiles and charges were slid onto waiting trays for the upper hoists. Eight ready rounds per gun were carried in racks behind the guns with the propellant charges stowed in lockers around the walls of the working chamber.
• ^As originally completed in 1915-16, all turrets had a maximum elevation of 12 degrees with the exception of Provence. As an experiment, it was decided during construction to increase the elevation of her No. 5 turret to 18 degrees. As a result, the ship was completed without guns in this turret and they were not installed until July 1917, a year after she entered service. During reconstruction between 1919 and 1923, the elevation of all turrets on all ships was increased to 18 degrees and increased again during the late 1920s to 23 degrees.
• ^The maximum elevation of the Quad turrets would almost certainly have been increased had the Normandie and Lyon classes been completed.
• ^Elevation was by Janney motor with selectable speeds. Manual backup was available with a maximum speed of 0.25 degrees per second. Guns could be elevated independently or yoked together.
• ^Training of the twin turrets was by Janney motor with selectable speeds. Manual backup was available with a maximum speed of 1.0 degrees per second.
• ^Training of the quad turrets was by Janney motor with selectable speeds. Manual backup was available with a maximum speed of 0.4 degrees per second.
• Twin turret personnel consisted of a supervisor, four gunlayers and trainers (including one spare), two loaders, two breech operators and two assistant breech operators. The armored hood at the rear of the turret contained the turret commander, a range taker operating a Barr & Stroud 6 ft (2 m) rangefinder, an assistant fire control director, a telephone operator, and two manipulateur Routin operators, a device manufactured by Brequet that used synchronized electric motors that allowed the central fire control station to directly set the range on the gunsights. Turrets 2 and 5, which were auxiliary fire control stations, had two additional operators, a ladder ranging assistant and operator responsible for transmitting the order to fire.
• The Bretagne class were equipped with electric motors driving hydraulic training and elevation gear. Chain rammers were also electric powered. Each gun had its own hoist which ran from the working chamber under the turret and a second pair of hoists ran down to the magazines. Gun loading cages had three compartments, the lower one for the projectile and the upper two each carrying two charges.
• For the proposed Jean Bart reconstruction, the coastal battery gun cradles would have allowed a maximum elevation of +35 degrees.
• Armor thickness for the Bretagne Class as given in "French Battleships of World War One:"
      Face: 8.9 in (22.5 cm) FH over two layers of 0.6 in (1.6 cm) plates
      Sides: 7.4 in (18.8 cm) FH over two layers of 0.6 in (1.6 cm) plates
      Rear: 7.4 in (18.8 cm) FH over two layers of 0.6 in (1.6 cm) plates
      Roof: Three layers of 0.9 in (2.4 cm) plates
      Floor: 2.4 in (6.0 cm) over two layers of 0.8 in (2.0 cm) plates
      Barbette (parapet tronçonnique) above weather deck: 6.1 in (15.4 cm) over two layers of 0.5 (1.2 cm) plates
• Armor thickness for the Normandie Class as given in "French Battleships of World War One:"
      Face: 11.8 in (30.0 cm) FH over two layers of 0.8 in (2.0 cm) plates
      Sides: N/A
      Rear: 9.3 in (23.5 cm) FH over two layers of 0.8 in (2.0 cm) plates
      Roof: 3.9 in (10.0 cm)
      Floor: N/A

"Naval Weapons of World War Two" by John Campbell
"The French Dreadnoughts: The 23,500 ton Bretagne Class" articles by Robert Dumas in "Warship Volume X"
"Naval Weapons of World War One" by Norman Friedman
"The Big Gun: Battleship Main Armament 1860-1945" by Peter Hodges
"French Battleships of World War One" by John Jordan and Philippe Caresse
"French Battleships: 1922 - 1956" by John Jordan and Robert Dumas
"French Battleships 1933 - 1970: An Illustrated Technical Reference" by Wayne Scarpaci
"Battleships of World War Two" by M.J. Whitley
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USS Nevada BB-36 DANFS Entry from Warships1 files
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Batterie de 340 de Cépet
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Special help from John Jordan and Helen Peeters

12 August 2006 - Benchmark
22 December 2009 - Added information on proposed Jean Bart reconstruction
07 January 2012 - Added pictures of Lorraine and APC shells
25 February 2012 - Added information on guns used as Coastal Artillery
05 August 2018 - Converted to HTML 5 format, added details on guns, ammunition and mountings, added photograph of Lorraine
05 January 2023 - Added information about replacement of sabotaged guns at Cap Cépet, updated formatting to the latest template