Britain
Hotchkiss 3-pdr (1.4 kg) [1.85"/40 (47 mm)] QF Marks I and II
Updated 15 December 2013
Hotchkiss 3-pdr guns were introduced in 1886 for locations where the 6-pdr gun was considered to be too heavy.  Used as anti-torpedo boat guns on most small cruisers built prior to World War I.  As did other nations, the British found that these small-caliber projectiles were too light to be effective and many guns were converted following World War I to sub-caliber training and saluting guns.  This last use meant that a number of these guns survived until World War II when they were converted back to shooting guns and used on MLs and other minor auxiliary warships.  An approximate total of 2,950 of these guns were in naval service, with about 1,950 of these still available in 1939.

Mark I was of monobloc construction while the Mark II was a built-up design.  Almost all surviving guns in 1939 were Mark I.
WNBR_3pounder_m2_Furious_pic.jpg

HMS Furious in 1898
Two 3-pdrs are in the fore-top
U.S. Naval Historical Center Photograph # NH 61062
WNBR_3pounder_H_mk1_Lorry_pic.jpg

Hotchkiss 3-pdr and machine gun being used on an Armored Lorry
IWM Photograph Q 14633
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Gun Characteristics
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Designation Hotchkiss 3-pdr (1.4 kg) [1.85"/40 (47 mm)] QF Marks I and II
Ship Class Used On Many
Date Of Design about 1885
Date In Service 1886
Gun Weight 528 lbs. (240 kg)
Gun Length oa 80.6 in (2.048 m)
Bore Length 74.1 in (1.881 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume 43 in3 (0.705 dm3)
Rate Of Fire 20 rounds per minute
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Ammunition
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Type Fixed
Weight of Complete Round HE - 5.7 lbs. (2.6 kg)
Projectile Types and Weights HE - 3.3 lbs. (1.5 kg)
Bursting Charge N/A
Projectile Length N/A
Complete Round 21.4 in (54.2 cm)
Propellant Charge World War I:  0.54 lbs. (0.24 kg) MD
World War II:  0.465 lbs. (0.211 kg) HSCT 134-055
World War II:  0.602 lbs. (0.273 kg) NF 029
Muzzle Velocity HE - 1,884 fps (574 mps) (new gun)
HE - 1,873 fps (571 mps) (average gun)
Working Pressure N/A
Approximate Barrel Life about 6,000 rounds
Ammunition stowage per gun Monitors of World War I carried 300 rounds per gun
Note:  During World War II, outfits were all HE, although some common rounds were used during the early part of the war.  Flashless was issued in the latter part of the war.
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Range
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Elevation With 3.3 lbs. (1.5 kg) HE Shell
20.7 degrees 6,500 yards (5,944 m)
45 degrees 7,900 yards (7,200 m)
Maximum AA Ceiling about 10,000 feet (3,000 m)
Effective AA Range about 1,200 yards (1,100 m)
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Mount / Turret Data
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Designation Single LA Mountings:  Mark I and Mark I*
Single HA Mountings:  Mark IV HA, Mark V HA and Mark VI HA
Weight  0.7 tons (0.8 mt)
Elevation Marks I and I*:  -5 / +25 degrees
Mark IV:  N/A
Mark V:  -5 / +70 degrees
Mark VI:  -5 / +60 degrees
Elevation Rate Manually operated, only
Train 360 degrees
Train Rate Manually operated, only
Gun recoil N/A
Note:  Marks I, I* and IV were pre-war and World War I mountings.  Marks V and VI were build during World War II.  The Mark VI used rubber recoil buffers.  Some Mark I mountings were converted to HA types and then designated as Mark IC HA.  These had an elevation range of -8 to +60 degrees.
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Data from
"Big Gun Monitors:  The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton
"Naval Weapons of World War Two" by John Campbell
Page History

27 February 2007 - Benchmark
12 February 2012 - Updated to latest template
15 December 2013 - Added picture of 3-pdr on a lorry