30mm DS30M Mark 2 Automated Small Calibre Gun The 30mm DS30M Mark 2 is a ship - protection system made by MSI Defence Systems consisting of a 30mm Mark 44 Bushmaster II cannon on an automated mount . It was designed to defend Royal Navy frigates from fast inshore attack craft armed with short - range missiles , rockets , rocket - propelled grenades , heavy machine guns or explosives . It replaced in this role the 30mm Oerlikon KCB gun on a DS30B manual mount . The DS30M has also been added to patrol boats and corvettes for the Iraqi and Omani navies respectively . Description . The DS30M Mark 2 system consists of a 30mm Mark 44 Bushmaster II on a fully automated mount with an off - mount electro - optical director ( EOD ) . The gun and the EOD are controlled from a remote operator console elsewhere on the ship . The " mount is a single cannon naval mount that is gyro stabilized , electrically operated and self contained gun mounting featuring a choice of cannon , control mode and sights . It has low magnetic , radar and IR signatures and excellent ergonomic availability , reliability and maintainability ( ARM ) . " In theory " the unique dual feed system of the Bushmaster series allows the operator to select different types of ammunition for use against a variety of targets . The safety , reliability and low life - cycle costs of the Bushmaster system added to its overall value . " However photographs show only a single ammunition feed . History . In August 2005 , the Maritime Gunnery and Missile Systems Integrated Project Team in the UK Ministry of Defence awarded MSI - Defence Systems ( part of MS International PLC ) a contract " to supply a total of 26 ASCG systems for retrofit to the RN ' s 13 Type 23 frigates as part of the wider littoral Defensive Anti - Surface Warfare ( ASuW ) upgrade programme . " This contract is worth more than £15 million ( USD30 . 7 million ) to MSI . The system is being bought because " Fleet Command and the UK Ministry of Defence ' s ( MoD ' s ) Directorate Equipment Capability ( Above Water Effect ) - DEC ( AWE ) - have identified a significant capability gap in the RN ' s ability to defend itself against fast attack craft and ' swarming ' fast inshore attack craft threats in the littoral . The latter include powerboats , interceptors , rigid inflatables and jet - skis variously equipped with short - range missiles , rockets , rocket - propelled grenades , heavy machine guns or explosives . " MSI undertook land - based trials at Eskmeals in Cumbria . In mid - 2007 MSI delivered the first two mountings , which were installed on HMS " Somerset " in August 2007 , and used in sea trials on gun ranges in the English Channel in starting in early October 2007 . In 2008 , a small analysis and management consultancy company CORDA ( part of BAE Systems ) was " awarded a £300 , 000 research contract by the UK MoD ' s Defence Technology and Innovation Centre ( DTIC ) to assess the level of protection British warships receive from small calibre 30mm guns . " CORDA ' s programme manager said : " What we are doing is looking at the performance of the Royal Navy ' s 30mm Automated Small Calibre Gun ( ASCG ) [ 30mm DS30M ] and what can be done to increase the level of protection it provides . ' . . . ' The ASCG system has significantly enhanced capability , but we have been asked to look at how improving tactics or integrating further technology could improve the performance of the system further . " The study used " simulator based operator trials and aims to quantify the performance of the entire weapon system when engaging multiple vehicles attacking together in a co - ordinated fashion . Results of the study are expected in early 2009 . " The trials were at the Maritime Warfare School at HMS Collingwood . CORDA worked in partnership with GE FANUC and BAE Systems ' Advanced Technology Centre , in conjunction with the DE & S Integrated Project Teams ( IPTs ) , with Dstl providing technical direction . Operators . United Kingdom The system is being fitted to the Royal Navy ' s Type 23 frigates , starting with HMS " Montrose " . In January 2009 the ship began a six - month refit at Rosyth , in which it was fitted with the 30mm DS30M Automated Small Calibre Gun systems in place of its older manually operated 30mm DS30B . Iraq The system is being fitted to fifteen Swiftships Model 35PB1208 E - 1455 patrol boat s building for the Iraqi Navy . ' Oman The system is being fitted to three Khareef Class Corvettes building for the Royal Navy of Oman . Thailand The system is being fitted to newly indigenous built Krabi class offshore patrol vessel ( Modified Port of Spain class corvette ) , Angthong class LPD ( Modified Endurance class LPD ) , Naresuan class frigates ( during MLU ) , and Inshore patrol vessel T . 991 - T . 996