Rose turret The Rose turret ( sometimes known as the Rose - Rice turret ) was a gun turret armed with two M2 Browning heavy machine guns which was fitted to some British Avro Lancaster heavy bombers in 1944 and 1945 . Development of the turret began in 1943 as part of a program to improve the Lancaster ' s defensive armament , but it did not enter production until late 1944 . The Royal Air Force ( RAF ) ordered 600 Rose turrets in June 1944 , and 400 were completed by the end of the Second World War in Europe . The turret was generally regarded as an improvement over previous designs , although its guns had a high rate of stoppages during combat . Development . When introduced to service , all of the Avro Lancaster ' s three gun turrets were fitted with . 303 Browning medium machine guns . The front and mid - upper turret were each fitted with two . 303 guns , and the rear turret had four . A small number of early Lancasters were also equipped with a ventral turret on the bottom of the fuselage fitted with two . 303s , but this turret was phased out from 1942 . The . 303 guns were soon regarded as being inadequate , however , and in 1942 the Air Staff identified a requirement to fit the Lancasters with a turret armed with more powerful . 50 calibre heavy machine guns " as soon as possible " ; this view was supported by Air Marshal Arthur Harris , the commanding officer of Bomber Command . A conference was held at the Air Ministry on 11 January 1943 to discuss the optimal armament for the Lancaster . The consensus view of the participants was that the aircraft should be fitted with two 20 mm cannon in its mid - upper turret , two . 303 guns in the forward turret and two . 50 calibre guns in the rear turret . At the conclusion of the conference , Air Vice Marshal Ralph Sorley , who was responsible for the RAF ' s technical requirements , stated that " every effort should be made to introduce the mid - upper and redesigned tail turrets in a year ' s time " and that the Lancaster ' s armament would be obsolete if this deadline was not met . Despite Sorley ' s views , development of an upgraded rear turret for the Lancaster proceeded slowly . Harris became frustrated with the slow progress of the project , and did not believe that the Air Ministry would be able to produce the turret in time . As a result , he decided to go outside the official channels and personally asked the small Gainsborough firm of Rose Brothers to develop a turret for the Lancaster ; this company had previously developed an improved gun mounting for the Handley Page Hampden bomber in 1940 upon a request from Harris . The Ministry of Aircraft Production subsequently offered to provide draughtsmen to help Rose Brothers develop the turret , but the head of the company turned down this offer and relied upon Air Vice Marshal Edward Rice for technical advice . Rice was one of the senior Bomber Command station commanders , and had travelled with Harris to visit Rose Brothers at the start of the project . He subsequently led No . 1 Group RAF . Harris obtained Sorley ' s agreement to support the development of what was by then known as the Rose turret in June 1943 . However , the firm Nash & Thomson , which produced the Lancaster ' s . 303 turrets , was also commissioned to develop a . 50 calibre armed turret as the Air Ministry and Ministry of Aircraft production did not want to rely upon Rose Brothers alone . Nash & Thompson ' s design was known as the FN82 . Development of the two new turret designs continued throughout 1943 , but neither was ready by early 1944 . The Rose turret shook severely during its early firing trials ; this was eventually attributed to poor workmanship of the turret ' s base ring . In June 1944 , the RAF placed an order for 600 Rose turrets after the problems with the design had been resolved . The turrets were built by hand at Rose Brothers ' factory at Gainsborough , and were eventually produced at the rate of one per day ; this rate was considered to be slow by the Air Staff . Production of the Rose turret ceased at the end of the war – by this time 400 had been completed . The FN82 took even longer to develop , and the first production model was completed in January 1945 . None of Bomber Command ' s Lancasters had been fitted with an FN82 by the end of the war . Characteristics . The Rose turret was a roomy design equipped with two M2 Browning heavy machine guns . The turret was driven by hydraulics , and the hydraulic system was easier to use than that in previous designs . The considerable internal space meant that the turret could also be fitted with two seats ; while a layout in which one man operated the guns while another fed targeting data into the gunsight computer was developed , this was not used in practice . An unusual feature of the Rose design was that the turret was not fully enclosed . While previous designs had perspex around the gun position , there was no protective shielding immediately in front of the gunner in the Rose turret , and it was open to the air . This feature reflected operational experience in which many Lancaster gunners had cut away parts of their turret in order to obtain a better view . Testing of the Rose turret found that the open design only reduced the temperature in the turret – which was typically very low – by four degrees Celsius compared with a closed design . As well as improving the gunner ' s view , this feature also made it easier for him to bail out of the aircraft in an emergency . Operational service . Rose turrets began to be used operationally from late 1944 . The turrets were mainly fitted to aircraft in No . 1 Group , though some were allocated to No . 5 Group . Most Lancaster rear gunners regarded the turret as an improvement because of its heavier firepower . However , the turrets proved to be less reliable than the older design , and research conducted by the Ministry of Air found that 60 percent of Rose turrets experienced gun stoppages during combat compared with 23 percent of the . 303 - equipped turrets . On the positive side , aircraft fitted with the Rose turret were found to be half as likely to be attacked by fighters as other Lancasters – the researchers suggested that " this may be accounted by the increased field of view from the turret which would assist evasion from attacks " . By the end of the war , 180 Rose turrets had been fitted to Lancasters . In his " Despatch on War Operations " , Harris stated that the turret was the only improvement made to the defensive armament of the RAF ' s heavy bomber s after 1942 , and argued that " those responsible for turret design and production displayed an extraordinary disregard " for Bomber Command ' s requirements .