"M" Class Monitor (1915)

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The nineteen "M" Class Monitors were launched in 1915. Fourteen of them had a 9.2-in gun, and five had two 6-in guns.

Overview of 19 vessels
Citations for this data available on individual ship pages
Name	Builder	Laid Down	Launched	Completed	Fate
M.15	William Gray & Company, Tees	1915	28 Apr, 1915	Jun, 1915	Torpedoed 11 Nov, 1917
M.16	William Gray & Company, Tees	1915	3 May, 1915	Jun, 1915	Sold 29 Jan, 1920
M.17	William Gray & Company, Tees	1915	12 May, 1915	Jul, 1915	Sold 12 May, 1920
M.18	William Gray & Company, Tees	1915	15 May, 1915	Jul, 1915	Sold 29 Jan, 1920
M.19	Raylton Dixon, Tees	1915	4 May, 1915	Jun, 1915	Sold 12 May, 1920
M.20	Raylton Dixon, Tees	1915	11 May, 1915	Jul, 1915	Sold 29 Jan, 1920
M.21	Raylton Dixon, Tees	1915	27 May, 1915	Jul, 1915	Mined 20 Oct, 1918
M.22	Raylton Dixon, Tees	1915	10 Jun, 1915	Aug, 1915	Sold Dec, 1938
M.23	Raylton Dixon, Tees	1915	17 Jun, 1915	Jul, 1915	Broken up 21 Apr, 1959
M.24	Raylton Dixon, Tees	1915	9 Aug, 1915	4 Oct, 1915	Sunk 29 Sep, 1936
M.25	Raylton Dixon, Tees	1915	24 Jul, 1915	Sep, 1915	Scuttled 16 Sep, 1919
M.26	Raylton Dixon, Tees	1915	24 Aug, 1915	Oct, 1915	Sold 29 Jan, 1920
M.27	Raylton Dixon, Tees	1915	8 Sep, 1915	Nov, 1915	Scuttled 16 Sep, 1919
M.28	Raylton Dixon, Tees	1915	28 Jun, 1915	Aug, 1915	Sunk 20 Jan, 1918
M.29	Harland & Wolff, Belfast	Mar, 1915	22 May, 1915	Jun, 1915	Sold 9 Sep, 1946
M.30	Harland & Wolff, Belfast	Mar, 1915	23 Jun, 1915	Jul, 1915	Sunk 13 May, 1916
M.31	Harland & Wolff, Belfast	Mar, 1915	24 Jun, 1915	Jul, 1915	Broken up 1948
M.32	Workman Clark & Company, Belfast	Mar, 1915	22 May, 1915	Jun, 1915	Sold 29 Jan, 1920
M.33	Workman Clark & Company, Belfast	Mar, 1915	22 May, 1915	Jun, 1915	Preserved

Armament

The ships were armed as follows.^[1]

As built:

M.15, M.16, M.17, M.18:

one 9.2-in B.L. Mark X gun on an altered Mark V mounting
one 12-pdr 18 cwt gun on P. V mounting on quarterdeck
one Hotchkiss 6-pdr H.A. gun
two Maxim machine guns

These first four used spare 9.2-in guns and mountings for the Drake and Cressy class, converted to provide 30 degree elevation.

M.19, M.20, M.21, M.22, M.23, M.24, M.25, M.26, M.27, M.28:

one 9.2-in B.L. Mark VIII gun on an altered C.P. III mounting
one 12-pdr 18 cwt gun on P. V mounting on quarterdeck
one Hotchkiss 6-pdr H.A. gun
two Maxim machine guns

These ten ships used 9.2-in guns removed from the Edgar class and altered to provide 30 degree elevation.

M.29, M.30, M.31, M.32, M.33:

two 6-in B.L. Mark XII on P. IX mountings
one 12-pdr 18 cwt gun on P. V mounting on quarterdeck
two Hotchkiss 6-pdr H.A. gun
four Maxim machine guns

These ships got their 6-in guns from those aft-most pairs that were not mounted in the Queen Elizabeth class battleships.

In November 1918:

M.21, M.23, M.24, M.25, M.26:

one 7.5-in

These guns were formerly from H.M.S. Swiftsure.

M.27:

one 6-in B.L.

Others: unchanged.

Footnotes

↑ The Technical History and Index, Vol. 4, Part 28. pp. 31, 32, 36.

Bibliography

Buxton, Ian L. (1978). Big Gun Monitors: The History of the Design, Construction and Operation of the Royal Navy's Monitors. Tynemouth: World Ship Society. (on Amazon.com and Amazon.co.uk).
Admiralty, Gunnery Branch (1917). The Director Firing Handbook. O.U. 6125 (late C.B. 1259). Copy No. 322 at The National Archives. ADM 186/227.
Admiralty, Technical History Section (1919). The Technical History and Index: Fire Control in H.M. Ships. Vol. 3, Part 23. C.B. 1515 (23) now O.U. 6171/14. At The National Archives. ADM 275/19.