French
155 mm/50 (6.1") Model 1920
Updated 14 August 2010
Unusual for this size gun in that the twin turrets had the guns individually sleeved.  They were also used in single casemate mountings on the carrier Bearn.

Built with an autofretted A tube, liner, jacket in two lengths and breech ring.  The Welin breech opened upwards.
WNFR_61-50_m1920_Duguay-Trouin_pic.jpg

Light Cruiser Duguay-Trouin
WNFR_61-50_m1920_Bearn_pic.jpg

Experimental Carrier Bearn
The 155 mm (6.1") guns are in the stern casemates
Photograph courtesy Charles Cordier
WNFR_3-50_m1922_Bearn_pic.jpg

Experimental Carrier Bearn in 1937
This view shows the bow 155 mm (6.1") casemate guns
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Gun Characteristics
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Designation 155 mm/50 (6.1") Model 1920
Ship Class Used On Duguay-Trouin, Jean d'Arc and Bearn classes
Date Of Design 1920
Date In Service 1926
Gun Weight 8.73 tons (8.87 mt)
Gun Length oa 316.9 in (8.050 m)
Bore Length 305.1 in (7.750 m)
Rifling Length 250.5 in (6.362 m)
Grooves (about 46) about 0.059 in deep x 0.295 in (1.5 mm x 7.5 mm)
Lands about 0.120 in (3 mm)
Twist Uniform RH 1 in 22.35
Chamber Volume 2,238 in3 (36.67 dm3)
Rate Of Fire
(see Note)		 3-5 rounds per minute
Note:  The expected rate of fire for the light cruisers was six rounds per minute, but three rounds per minute was the usual rate of fire.  The Permanent Trials Board criticized the complicated ammunition supply system.
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Ammunition
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Type Bag
Projectile Types and Weights SAP - 124.6 lbs. (56.5 kg)
HE, internal nose fuze - 130.1 lbs. (59.0 kg)
HE, base fuze - 124.6 lbs. (56.5 kg)
Bursting Charge SAP - about 6.5 lbs. (2.9 kg)
HE, internal nose fuze - 12.4 lbs. (5.6 kg) picric acid
HE, base fuze (original) - about 7.4 lbs. (3.3 kg) picric acid
HE, base fuze (later) - about 6.5 lbs (2.9 kg) cast TNT
Projectile Length SAP - 31.5 in (80 cm)
HE - about 30.5 in (77.5 cm)
Propellant Charge 43.67 lbs. (19.81 kg) BM11
Muzzle Velocity New gun with SAP:  2,854 fps (870 mps)
New gun with HE, base fuze:  2,835 fps (864 mps)
Average gun:  2,789 fps (850 mps)
Working Pressure about 19.4 tons/in2 (3,050 kg/cm2)
Approximate Barrel Life about 700 rounds
Ammunition stowage per gun
(see Note 2)		 Duguay-Trouin:  125 rounds
Others:  N/A
Notes:

1) The propellant charge was in halves and was rectangular in shape.

2) Duguay-Trouin outfit was 1,000 HE, 60 illumination for upper turrets, no illumination for lower turrets, 40 practice rounds for upper turrets and 120 practice rounds for lower turrets.
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Range
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Elevation With 124.6 lbs. (56.5 kg) SAP Shell
Range @ 5 degrees 9,400 yards (8,600 m)
Range @ 10 degrees 14,220 yards (13,000 m)
Range @ 30 degrees 24,060 yards (22,000 m)
Range @ 40 degrees 27,340 yards (25,000 m)
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Elevation With 124.6 lbs. (56.5 kg) HE Shell
Range @ 40 degrees 28,543 yards (26,100 m)
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Mount / Turret Data
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Designation Single Mounts
   Bearn (8):  N/A

Two-gun Turrets
   Duguay-Trouin (4) and Jean d'Arc (4):  Model 1921
Weight  Single Mount:  N/A
Twin Mount:  about 78.7 tons (80 mt)
Elevation -5 / +40 degrees
Elevation Rate about 6 degrees per second
Train Model 1921:  -140 / +140 degrees
Others:  N/A
Train Rate 6.4 degrees per second
Gun recoil Nominal:  19.7 in (50 cm)
Maximum:  21.7 in (55 cm)
Notes:

1) Training and elevation for the two-gun turrets were electrically powered.  RPC for training was slated to be added to these but cancelled upon France's surrender in 1940.

2) The gun axes were 59 in (150 cm) apart.
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Data from
"Naval Weapons of World War Two" by John Campbell
Article in Warships International No. 3, 2001, "French Light Cruisers" by Jean Guigliani and Albert Moreau
"Navies of the Second World War - The French Navy" by Henri le Masson
"Cruisers of World War Two" by M.J. Whitley
Page History

24 March 2007 - Benchmark
14 August 2010 - Added additional projectile weights and burster weights