330 mm/50 (13") Model 1931
Updated 29 November 2009

These guns were used to arm the first French capital ships built since World War I, the Dunkerque class.  These weapons had a high muzzle velocity, which gave them long range and good vertical armor penetration at the cost of having poor deck penetration.  They were mounted in quad turrets, which were really more of a dual-twin arrangement.  The design of the quad turret was based upon one designed but never built for the Normandie class.

Although equipped with RPC, the Sautter-Harlé-Blondel gear for these turrets was apparently far from satisfactory.  As the guns were closely spaced together, these ships also suffered from problems with excessive dispersion.

The dual quad-gun turret arrangement was calculated to be 27.6% lighter than a quad twin-gun arrangement, but it did mean that a single hit could eliminate half of the main battery.

The construction of these weapons is not clear, but it is believed to have been similar to that of the 380 mm/45 (14.96") guns used on the Richelieu.  This would make the construction a loose autofretted liner and A tube reinforced at the breech by a single row of short hoops along with an outer jacket.  The breech mechanism was a Welin screw breech block, hydro-pneumatically powered and balanced by counterweights.  The breech plug opened upwards.  Actual bore length was 50.44 calibers.

Some of the APC shells for these guns were converted to aircraft AP bombs.

A note on sources:  "Battleships:  Allied Battleships in World War II" and "Battleships of the World 1905-1970" list this weapon as "330 mm/52" but, as noted above, the actual bore length was 50.44 calibers.


Dunkerque in 1939
Photograph courtesy of Charles Cordier


Strasbourg in 1938


330 mm APC being brought aboard Dunkerque
The lack of a nose fuze shows that this is an OPf Model 1935
ECPA(D), Ft. d'Ivry Photograph

Gun Characteristics
Designation 330 mm/50 (13") Model 1931
Ship Class Used On Dunkerque Class
Date Of Design 1931
Date In Service 1939
Gun Weight 155,503 lbs (70,535 kg)
Gun Length oa 676.0 in (17.170 m)
Bore Length 655.3 in (16.645 m)
Rifling Length 548.8 in (13.940 m)
Grooves (80) 0.126 in deep x 0.304 in (?) (3.2 mm x 7.73 mm)
Lands 0.205 in (?) (5.2 mm)
Twist Uniform RH 1 in 25.57
Chamber Volume 17,880 in3 (293 dm3)
Rate Of Fire 1.5 - 2 rounds per minute
Note:  The intended rate of fire was 3 rounds per minute.  However, the shell supply arrangements in the shell rooms proved to be inadequate and the designed ROF was never met.
Type Bag
Projectile Types and Weights
(see Notes 3 and 4)
APC - 1,235 lbs. (560 kg)
HE - 1,151 lbs. (552 kg)
Bursting Charge APC - 44.7 lbs. (20.3 kg)
HE - 140 lbs. (63.5 kg)
Projectile Length 65 in (165 cm)
Propellant Charge 423 lbs. (192 kg) SD19
Muzzle Velocity APC - 2,854 fps (870 mps)
HE - 2,904 fps (885 mps)
Working Pressure 20.3 tons/in2 (3,200 kg/cm2)
Approximate Barrel Life 250 rounds
Ammunition stowage per gun Turret I:  114 rounds
Turret II:  110 rounds

1) Propellant charges were in quarters.

2) Aircraft AP bomb weighed 1,235 lbs. (560 kg) and was designated as M1939.

3) Actual projectile designations:  APC - OPf Mle 1935 (no Dye) and OPfK Mle 1935 (with Dye).  HE - OEA Mle 1935.

4) HE projectiles may not have actually entered service.

5) APC had a radius head of 6crh.  The large burster of this shell, 3.6% of total weight, is thought to indicate that it was intended primarily for use against the lightly armored German Panzerschiffes.

With 1,235 lbs. (560 kg) APC
Striking Velocity
Angle of Fall
4.3 degrees
10,936 yards (10,000 m)
2,261 fps (689 mps)
7.2 degrees
16,404 yards (15,000 m)
2,005 fps (611 mps)
10.2 degrees
21,872 yards (20,000 m)
1,755 fps (535 mps)
14.8 degrees
27,340 yards (25,000 m)
1,614 fps (492 mps)
19.6 degrees
32,808 yards (30,000 m)
1,529 fps (466 mps)
25.4 degrees
38,276 yards (35,000 m)
1,512 fps (461 mps)
35.0 degrees
45,604 yards (41,700 m)
With 1,151 lbs. (522 kg) HE Shell
35.0 degrees
44,401 yards (40,600 m)
Armor Penetration with 1,235 lbs. (560 kg) APC Shell
Side Armor
Deck Armor
0 yards (0 m)
28.08" (713 mm)
25,153 yards (23,000 m)
13.46" (342 mm)
3.47" (105 mm)
30,114 yards (27,500 m)
11.48" (292 mm)
4.32" (110 mm)
Note:  This data is from "Battleships:  Allied Battleships in World War II" for a muzzle velocity of 2,854 fps (870 mps) and is based upon the USN Empirical Formula for Armor Penetration.
Mount / Turret Data
Designation Quad Mount
   Dunkerque (2):  St Chamond Model 1932
(see Note 2)
1,473 tons (1,497 mt)
Elevation -5 / +35 degrees
Rate of Elevation 6 degrees per second
(see Note 7)
Turret I:  +/- 143 degrees 
Turret II:  +/- 150 degrees
Rate of Train 5 degrees per second
Gun Recoil 45.3 in (1.15 m)
Loading Angle
(see Note 8)
Any angle

1) These guns were sleeved in pairs.  There was apparently some adjustment between the guns in a pair, possibly for alignment purposes.  Dunkerque was the first French battleship to have RPC for training and elevation.  The turrets were powered by Léonard electric servo-motors with hydraulic drive with Sautter-Harlé-Blondel (SHB) RPC gear.  However, the SHB equipment was found to be unreliable, synchronization between the directors and turrets was poor and manual intervention was needed for fine adjustment.  In addition, the servo motors were underpowered which resulted in slow tracking speeds and frequent breakdowns.  Major problems were found on trials and even after modifications the system never worked properly.  Two 100 HP training motors were provided for each turret, with only one needed at a time.  One 75 HP elevation motor was provided for each pair of guns.

2) These mountings were developed by St Chamond and were electrically powered.  The supporting ball race contained 152 balls of 7.17 in (18.2 cm) diameter.  The magazines and shell rooms for each pair of guns were on the same deck on opposite sides of the barbette and on two levels, with those for the port pair of guns on the reinforced inner bottom and those for the starboard side on the deck directly above.  Ammunition supply from the magazines was by dredger hoist, one for each pair of guns.  Ammunition was transferred in the working chamber to the gun loading cages of the upper hoists.  Each gun had its own hoist and the cages had three compartments, the lowest one for the shells while each of the upper compartments held two charges.  Although there is only one weight given for all four turrets, it should be noted that the rear of "B" turret on Dunkerque had 1 cm thinner armor than "A" turret and that Strasbourg had 3 cm thicker face armor and 1 cm thicker roof armor than the turrets on Dunkerque.  For these reasons, I would conclude that there were at least three different weights among the four turrets.

3) The gunhouse was divided internally by a 4 cm (1.6") bulkhead.  This ran down into the working chamber where it was thinned down to 2.5 cm (1").

4) Heavy leather blast bags were fitted to the main gun embrasures in 1939.

5) Two 100 hp training motors were in each mounting, either one of which could be used to train the turret.  There were two elevation motors, each rated for 75 hp.

6) The gun axis in each pair were 66.5 in (169 cm) apart while the two inner guns were 100 in (254 cm) apart.

7) These gun arcs should be regarded as approximate as various official plans give differing figures.  Some of this may be due to concerns about blast effects on the ship fittings.

8)  An electric chain rammer was carried on an extension of the gun cradle and theoretically permitted loading and any angle of elevation.  In practice, it was found that shells jammed in the breech at higher elevations when the other guns were firing.  As a result, loading usually took place at angles no more than 15 degrees.

Data from
"Battleships of the World 1905-1970" by Siegfried Breyer
"Naval Weapons of World War Two" by John Campbell
"Battleships:  Allied Battleships in World War II" by W.H. Garzke, Jr. and R.O. Dulin, Jr.
"The Big Gun:  Battleship Main Armament 1860-1945" by Peter Hodges
"French Battleships:  1922 - 1956" by John Jordan and Robert Dumas
"Battleships of World War Two" by M.J. Whitley
Page History

23 May 2006 - Benchmark
29 November 2009 - Added picture of APC, data on gun construction, projectiles, turret arrangements and RPC equipment