12-pdr [3"/50 (7.62 cm)] 18cwt QF Mark I
Updated 29 November 2015

Anti-torpedo boat gun of the late 1800s.  Some of these were converted to AA guns during World War I.  None appear to have survived long enough to serve during World War II.

HMS Dreadnought about 1906-1907
12-pdr 18cwt QF Mark I guns may be seen atop the forward and rear turrets.  These were given light shields shortly before the start of World War I
U.S. Naval Historical Center Photograph # NH 63367


7.5" (19 cm) turrets for HMS Shannon under construction with 12-pdr 18cwt guns on top
Library of Congress Photograph LC-DIG-ggbain-19618
Click on this picture for a larger image
This image is also at The Vickers Photographic Archive as 6486

Images at Australian War Memorial

Picture of 12-pdr 18cwt on HMAS Swan

Picture of 12-pdr 18cwt as AA gun on barge

Gun Characteristics
Designation 12-pdr [3"/50 (7.62 cm)] 18cwt QF Mark I
Ship Class Used On King Edward VII (last three units), Lord Nelson, Dreadnought and Minotaur classes

Monitors - Abercrombie, Lord Clive, Marshal Ney and Erebus classes, plus M15 through M28

Date Of Design N/A
Date In Service N/A
Gun Weight 0.9 tons (1.0 mt)
Gun Length oa 154.7 in (3.929 m)
Bore Length about 150 in (3.810 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire 15 rounds per minute
Type Separate
Weight of Complete Round N/A
Projectile Types and Weights HE 2crh - 12.5 lbs. (5.67 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 2.75 lbs. (1.25 kg) MD
Muzzle Velocity 2,600 fps (792 mps)
Working Pressure N/A
Approximate Barrel Life 1,200 rounds
Ammunition stowage per gun Monitors:  300 rounds
Lord Nelson:  230 rounds
Dreadnought:  300 rounds
Others:  N/A
Elevation With 12.5 lbs. (5.67 kg) HE Shell
Range @ 20 degrees 9,300 yards (8,500 m)
Mount / Turret Data
Designation Single Mounting

Africa (14), Britannia (14), Hibernia (14), Lord Nelson (24), Dreadnought (28), Minotaur (18):  PIV

Monitors generally had 1 or 2 guns

Weight  1.71 tons (1.74 mt)
Elevation -10 / +20 degrees
Elevation Rate Manually operated, only
Train 360 degrees
Train Rate Manually operated, only
Gun recoil N/A

1) Some guns were later converted for HA use.  From the Australian War Memorial picture H18888 noted above, these appeared to have used very simple, extemporized mountings.

2) HMS Dreadnought completed with 28 guns but this was increased to 31 by fitting additional guns to the roofs of the centerline turrets.

3) The Lord Nelson class was reduced to 18 guns during the war with the removed guns used on other warships.

Data from
"British Battleships of World War One" by R.A. Burt
"Big Gun Monitors:  The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton
"British Battleships:  1860 - 1950" by Oscar Parkes
Special help from Rod Butcher
Page History

28 December 2008 - Benchmark
04 February 2014 - Added ammunition stowage and number of guns
21 May 2014 - Added ammunition stowage for Lord Nelson class
29 November 2015 - Changed Vickers Photographic Archive links to point at Wayback Archive