BL 8 - inch howitzer Mk VI – VIII The BL 8 - inch howitzer Marks VI , VII and VIII ( 6 , 7 and 8 ) were a series of British artillery siege howitzers on mobile carriages of a new design introduced in World War I . They were designed by Vickers in Britain and produced by all four British artillery manufacturers , but mainly by Armstrong , and one American company . They were the equivalents of the German 21 cm Morser and in British service were used similarly to the BL 9 . 2 - inch howitzer , but were quicker to manufacture , and more mobile . They delivered a 200 lb shell to 12 , 300 yards . They had limited service in the British Army in World War II before being converted to the new 7 . 2 - inch calibre . They also equipped a small number of Australian and Canadian batteries in World War I and by the US Army in that war . They were used in small numbers by other European armies . Design and variants . 8 inch was a calibre adopted in the First World War by the British Army . The Marks VI , VII and VIII ( 6 , 7 and 8 ) were a new design and should not be confused with the stopgap early Marks 1 - 5 of 8 - inch howitzer , which used shortened and bored - out naval 6 - inch gun barrels . Mark VI . The Vickers design , very similar to their 6 - inch howitzer , was approved in August 1915 and first substantial order placed in March 1916 for 50 howitzers , with 30 more in the autumn . It was 4 - 5 tonnes lighter than the improvised 8 - inch " howitzers " Mks I - V . The Mk VI barrel was of built - up construction and was 14 . 7 calibres ( 117 . 7 inches ) long , with a range of 10 , 745 yards ( 9 , 825 m ) . Mark VII . Introduced July 1916 . Mk VII had a longer barrel ( 17 . 3 calibres , or 138 . 4 inches ) of wire - wound construction and increased the range to 12 , 300 yards ( 11 , 250 m ) . The new barrels turned out to have short lives and suffered from cracked A tubes ( the inner rifled layer of the built - up barrel ) . Mark VIII . Mk VIII incorporated various small improvements and a thicker and stronger barrel . Combat use . 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 . By the start of World War II some Mk 8 were still in use and were used in France in May to June 1940 . After the Fall of France , remaining guns were used for training only . The advent of the BL 7 . 2 - inch howitzer meant that remaining 8 - inch barrels were relined to 7 . 2 inch . With no guns left , they were , not surprisingly , declared obsolete by July 1943 . Use by United States . Versions of Mk 6 were manufactured in the United States by Midvale Steel and Ordnance Co , Nicetown , Pa . during World War I , initially supplied to Britain and then used to equip US forces when it entered the war . A US Mk 8½ version was also manufactured and adopted in US service from October 1918 . Quoting from the US Army manual of 1920 on artillery in US service : - " 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 1 / 2 , the difference between the two being that the powder chamber walls of the Mark VII proved to be too thin , while the Mark VIII 1 / 2 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 1 / 2 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 1 / 2 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 1 / 2 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 1 / 2 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 12½ feet [ compared to Mk VI 10½ 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 44th , 51st , and 59th Regiments were in action with British - manufactured versions . Use by Finland . During the Russo - Finnish Winter War Finland found itself in dire need of heavy artillery . Thirty - two " 8 in Howitzer Mk 7 ( Vickers Mk 6 ) " 8 - inch howitzers were bought from the United States in 1939 but arrived too late to see action in the war . The howitzers were given the designation 203 H 17 ( 203 mm , Haupitsi [ Finnish for howitzer ] , 1917 ) and were first issued to three heavy artillery battalions ( 1st , 2nd and 3rd ) , which later were re - organised into six heavy artillery batteries ( 11th , 12th , 13th , 14th , 15th and 16th ) . The howitzer with its durable design was well liked by the Finnish army . Thirteen of these howitzers were lost in the battles during the summer of 1944 , eight of these belonged to Heavy Artillery Battery 4 and were lost at Valkeasaari on 10 June , while the other five belonged to Heavy Artillery Battery 3 , located northeast of Lake Ladoga . The howitzers were stored after the war and were stricken from the lists in the late 1960s .