Vickers K machine gun " Not to be confused with the Vickers light machine gun " The Vickers K machine gun , known as the Vickers Gas Operated ( Vickers G . O . ) in British service , was a rapid - firing machine gun developed and manufactured for use in aircraft by Vickers - Armstrongs . The high rate of fire was needed for the small period of time when the gunner would be able to fire at an attacking aircraft . Development . The Vickers K was a development of the Vickers - Berthier ( VB ) light machine gun , adopted in 1932 by the Indian Army . The VB , like the Bren light machine gun , used a tilting locking breechblock . However , unlike the Bren , the VB locked its breech only at the last moment of forward travel and this enabled the development of the Vickers K also known as the " Vickers Gas Operated " ( VGO ) or " Vickers GO " . With lighter moving parts and the VB locking design , the Vickers K had an adjustable rate of fire between 950 and 1 , 200 rounds per minute ; faster than the German MG34 . The weapon was adopted for British service as the VGO . It was test - flown with a large 300 - round drum , and beat the . 303 Browning in reliability . However , the wide drum would have caused problems to accommodate , since it would have interfered with wing structures . When the belt - fed Browning Mark II was selected as the standard machine - gun armament for RAF aircraft , the VGO became redundant for the RAF . It continued to be used by the Fleet Air Arm until 1945 Variants . Some were made in 7 . 7mm for the Belgians before the war and at least one example survives in a European museum . VGO No . 2 Mk . 1 . . Originally intended for RAF airfield defense units , these guns were remanufactured from original Vickers G . O . No . 1 Mk . 1 aircraft guns . A number of these ‘ Vickers G . O . Land Service ’ machine guns found their way to a variety of British Commando and reconnaissance units which operated in Europe during 1944 and 1945 . Once the war was over , all Vickers GO machine guns were declared obsolete and subsequently removed from service . The Vickers class K / Vickers G . O . machine gun is a gas operated weapon , firing from an open bolt in full automatic mode only . Its gas cylinder is located below the barrel , and a long stroke gas piston operates a vertically tilting bolt . Feed is from top - mounted flat pan magazines with a nominal capacity of 100 rounds , although it was customary to load only 96 or 97 rounds to ensure reliable feeding . The gun is fitted with a single spade grip at the rear of receiver , with trigger to control fire . In ground applications , it was normally mounted on single or twin pintle mounts on various jeeps and trucks . Vickers GO No . 2 Mk . 1 Land Service . The Land variant has the spade grip replaced with a short stock at the rear and a pistol grip with trigger below the receiver . A short forend or a folding carrying handle are added below the gas cylinder , and a folding bipod is attached to the gas block . New iron sights are provided on folding bases . Vickers G . O . Camera Gun . A camera gun version was made for training . The body was of cast metal . The grip and trigger mechanism were realistic . Gunners in training exposed film when " shooting " at attacking aircraft and these images were analysed later . This was a technique developed in World War I with Lewis Camera Guns . Combat use . The Vickers K was fitted to a number of two - and three - seater aircraft in RAF service such as the Fairey Battle and Handley Page Hampden . It was also used in gun turret s , such as the dorsal turret in the Bristol Blenheim , the nose turret in the Armstrong Whitworth Whitley and the rear turret of the Fairey Battle . It was the standard Royal Navy Fleet Air Arm " Telegraphist Air Gunner " machine gun , on British built carrier ( Torpedo Strike Reconnaissance ) aircraft - the Fairey Swordfish , the Fairey Albacore and the Fairey Barracuda . As supplies of air - cooled . 303 in ( 7 . 7 mm ) Browning machine guns increased the Vickers G . O . was phased out of use with the RAF . These machine guns were then reallocated from RAF stocks to units of the British and Commonwealth armies . The gun continued in service with the Fleet Air Arm , and its last recorded use by the navy was by 812 Squadron RNAS Barracudas in anti piracy patrols off Hong Kong in October 1945 . The Long Range Desert Group was supplied with large numbers of the Vickers G . O . for use on its vehicles . They were used in single or custom built twin mountings . The Special Air Service adopted it for their hit and run tactics , mounting it in pairs on their jeeps . Over the years , it was assumed by some that the latter services took the phased - out VGO because they could obtain no other suitable machine guns but with its high rate of fire and low - friction locking design ( which proved resistant to jams from sand ) , the LRDG and SAS found the G . O . markedly superior to either the . 303 in ( 7 . 7 mm ) water - cooled Vickers or the Bren gun . In a similar manner , the Airborne Reconnaissance Squadron of the Reconnaissance Corps mounted the VGO on jeeps when they were attached to the 1st Airborne Division during Operation Market - Garden in September 1944 . Royal Marine and Army Commandos used the VGO for infantry support / squad automatic weapon briefly around D - Day . In military terminology , it was known as Gun , Machine , Vickers G . O . . 303 - inch . In the Coastal Forces of the Royal Navy , the Vickers K began to replace the Lewis gun on board Motor Torpedo Boats , Motor Launch es and other light craft , from 1942 onwards .