2 - inch mortar The Ordnance SBML 2 - inch mortar , or more commonly just " 2 - inch mortar " , was a British mortar issued to the British Army and the Commonwealth armies that saw use during the Second World War and later . It had the advantages of being more portable than larger mortars which needed vehicles for them to be carried around , but the ' 2 - inch ' gave greater range and firepower than rifle grenade s . History . The British Army had two types of mortar in service at the outbreak of the Second World War , one of which was the 2 - inch weapon for use with infantry platoons . The 2 - inch mortar had been developed during the 1930s after the British Army had inspected weapons of a similar calibre in service with other European countries , including the Spanish 50mm version . Although deemed unsuitable for the British Army as it stood , the Spanish mortar did serve as the starting point from which the Armament Research Department could begin development of its own weapon . In November 1937 ten examples of the new mortar were readied with 1 , 600 rounds each of high - explosive and smoke bombs . The resulting trials confirmed the reliability and dependability of the weapon . The Director of Artillery ordered it to be placed in production in February 1938 , only four months after the initial field trials , which meant that by 1939 some 500 of the weapons and their associated ammunition were already established in service as the Mk II , with crews trained in its use . Over the duration of the war the 2 - inch mortar was developed into no fewer than eight separate marks , from which also stemmed a number of other variations . Some were successful and others less so ; one of the latter , the ' Weston ' version , was developed in 1944 , but was found to be less than satisfactory when used on soft ground . This weapon had the advantage of being fitted with an automatic recocking feature of the firing mechanism , but despite this it was withdrawn from use . The standard service version of the mortar had a barrel length of and could fire a high explosive bomb weighing out to a range of 500 yards . With such a short barrel the normal firing method , where the bomb was dropped down the tube and a pin in the base of the barrel struck the detonator in the tail of the bomb , would not work so firing was by a small trigger mechanism at the breech . Originally the mortar was fitted with a large collimating sight with elevating and cross - level bubbles , but this was soon dropped as unnecessary for front - line use . It was replaced instead with a simple white line painted up the length of the barrel . The firer only had to line this up in the direction of the target and fire a number of bombs for effect . Whilst this method of operation may sound rather haphazard , it worked well and the practice continued long after the war . The mortar evolved in other directions too , with the original large base plate being replaced by a simple curved model , to give it a combat weight of . Due to its small size , and for simplicity , the mortar had no forward strut or bipod that most larger designs needed . The barrel would be held at the correct angle by one soldier while the other loaded and fired the round . It could achieve a firing rate of some eight rounds per minute . The bombs were cylindrical with a ( perforated ) four finned tail . For the HE projectile an impact fuze was fitted in the nose of the bomb . The illuminating round weighed , the smoke round weighed . A whole range of other ammunition was also developed , including a specialised bomb that cast a lightweight explosive - filled net over minefields which could be detonated , clearing a path . Variants of the weapon itself included the Mk VII * with a shortened barrel , for use by airborne units , the Mk VII for use in Universal ( Bren Gun ) Carriers and the Mk III used as a smoke discharger in tanks . Post war , the 2 - inch mortar was kept in service to fire smoke and illuminating rounds . It remained in service until the late 1980s when it was replaced by the L9A1 51 mm Light Mortar . Ammunition type ( + round weight and colour ) . note : the Multi Star available in white , red , green , and red / green mixed Modern Variants . India ’ s Ordnance Factory Board ' s 51mm E1 mortar is a copy of the 2 - inch British mortar of World War II ; it is still in production and service in India .