United Kingdom World War I Early problems of stability on very hard or soft ground became apparent with the Mk VI, leading to the recoil system not functioning correctly. A Commission went to France to investigate, and a special level "Vickers platform" was adopted, to which the wheels and trail were secured for accurate shooting. A major change in the line of shooting required the platform to be relaid. Setting up and adjusting the platform was labour-intensive. The US manual describes it: The platform consists of wooden beams which assemble to form a triangular platform. The spade must be removed and a special bracket fitted on the trail when using this platform. This bracket travels in a groove which gives a bearing for the bracket and also provides a means of traversing the piece 52° on the platform. The main objects in the use of the firing platform are: To provide a reliable support for the wheels and rear end of the trail, so as to prevent sinking or movement when firing on soft ground; to ensure the gun remaining on the target when firing; and to provide means for shifting the trail transversely through an angle of 52° (26° each side of center). By using the traversing gear on the carriage a total traverse of 30° on each side of the center is obtainable... The carriage wheels rest on steel plates on the wheel platform and are guided by curved-steel angles which prevent lateral movement of the gun off the target when in action. When the firing platform is used, the float plate, with spade attached, which is bolted to the underside of the trail, is removed and another float plate, having a thrust bracket attached, is bolted in its place. At the end of
World War I on the Western Front, Canada had two 6-gun batteries, Australia 1, Britain 37. British 8-inch howitzer batteries serving in other theatres at the Armistice were: UK 1 (6 guns), Macedonia 1 (4 guns) and 2 guns in Palestine
World War II At the start of World War II, some Mk 8s were used in France from May to June 1940. In March 1940, 266 weapons were authorised for transfer from the United States to the British.
United States Versions of the Mk 6 were manufactured in the United States by
Midvale Steel and Ordnance Co,
Nicetown, Pennsylvania during World War I, initially supplied to Britain and then used to equip US forces when it entered the war. These were designated the M1917 in US service. A US Mk 7 and Mk version was also manufactured and adopted in US service from October 1918 as the M1918. "The 8-inch howitzer materiel is called the "Vickers" model of 1917, of which there are in use two types, the Mark VI and Mark VII. The main differences between the Mark VI and Mark VII being that the former has a lower muzzle velocity and consequently a shorter range than the latter, also that the Mark VII has a barrel of the "wire wound" construction, whereas the Mark VI type is of the "built up" construction... The Mark VII has lately been superseded by a Mark VIII , the difference between the two being that the powder chamber walls of the Mark VII proved to be too thin, while the Mark VIII overcomes this defect by having thicker powder chamber walls... ... the average life of the 8-inch howitzer, Mark VI, [before the barrel needs relining] is 7,800 rounds, while that of the Mark VIII is 3,000 rounds. The Mark VI howitzer has a muzzle velocity of 1,300 feet per second and a maximum range of 10,760 yards and is of British design and both British and American manufacture. The Mark VII howitzer has a muzzle velocity of 1,525 feet per second and maximum range of 12,280 yards and is of British design and manufacture. The Mark VIII is an American modification of the British wire-wound Mark VIII howitzer to permit of a built up type of construction and is strictly of American manufacture. The Mark VIII has the same muzzle velocity and range as the Mark VIII. Due to the combination of British and American manufacture, there are several types of breech mechanism in service; the two main types are the T and the French percussion type... The Mark VIII howitzer is also of the built-up-construction type, but differs from the Mark VI howitzer in that it consists of two tubes, an inner and an outer, over which is shrunk the jacket. The jacket in this case supports the howitzer, without the use of guide rings. A breech ring is shrunk on over the jacket and carries a lug for connecting the gun to the recoil mechanism. A breech bushing similar to that of the Mark VI is fitted for the breech mechanism. The total length of this howitzer is about feet [compared to Mk VI feet] and its maximum range is approximately 12,360 yards. This howitzer is mounted on the Mark VII carriage". The 58th Regiment
Coast Artillery Corps (C.A.C.) was in action in France in the final days of
World War I with the US-manufactured Mk 6, and the
44th,
51st, and
59th Regiments were in action with British-manufactured versions. An additional six regiments, three with each type of gun, are described as being nearly ready for the front at the time of the Armistice. Each regiment had an authorised strength of 24 guns. A total of at least 285 M1917 (Mark 6), 116 M1918 (Mark 7), and 61 M1918 (Mark ) weapons were acquired by the US Army, plus 16 for the US Marine Corps. 52 weapons were purchased from the British beginning in January 1918; subsequent inventory figures indicate they were in addition to these totals. By 1922, the 8-inch howitzers were withdrawn from active units and stored as war reserves. A 1926 inventory showed 508 howitzers and 646 carriages in Army hands. An approximate total of 530 howitzers were acquired. In 1933, some of the howitzers' Asbury breech mechanisms were used in developing the 155 mm gun T3, eventually the
M1 "Long Tom". In 1934, the Marine Corps weapons were transferred to the Army. In March 1940, 466 weapons were on hand; 266 of these were authorised for transfer to the British. A further 32 weapons were transferred to Finland in September 1940. In 1941, the remaining weapons were authorised for transfer to the British under
Lend-Lease. None of these weapons were donated as war memorials, and none survive in the United States. == Variants ==