British
4"/33 (10.2 cm) QF Mark XXIII
Updated 05 September 2006
A light weight gun for submarines.  Developed too late for service during World War II.

Constructed with a monobloc loose barrel and breech ring.  The bore and external parallel section were nickel plated and zinc protective plates were on the breech ring and horizontal sliding breech block.  A total of thirty-one guns were manufactured.  Actual bore length was 33.04 calibers.
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Looking for a picture
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Images at The Vickers Photographic Archive

See XXIII

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Gun Characteristics
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Designation 4"/33 (10.2 cm) QF Mark XXIII
Ship Class Used On A class and a few T class submarines
Date Of Design about 1944
Date In Service 1946
Gun Weight 0.7 tons (0.76 mt)
Gun Length oa 137.6 in (3.495 m)
Bore Length 132.2 in (3.358 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume 183 in3 (3.00 dm3)
Rate Of Fire about 15 rounds per minute
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Ammunition
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Type Fixed
Projectile Types and Weights HE - 35 lbs. (15.9 kg)
HE - 38.5 lbs. (17.5 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 3.75 lbs. (1.7 kg) NF052
3.88 lbs. (1.8 kg) NF052
Muzzle Velocity For 35 lbs. (15.9 kg) - 1,791 fps (546 mps)
For 38.5 lbs. (17.5 kg) - 1,745 fps (532 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A
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Range
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Elevation With 35 lbs. (15.9 kg) HE Shell
Range @ 30 degrees 12,080 yards (11,050 m)
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Mount / Turret Data
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Designation SII
Weight  N/A
Elevation -5 (?) / +30 degrees
(may have later been altered to +20 degrees)
Elevation Rate Manually operated, only
Train 360 degrees
Train Rate Manually operated, only
Gun recoil N/A
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Data from
"British Naval Guns 1880-1945 No 18" article by John Campbell in "Warship Volume X"