1 . 59 - inch Breech - Loading Vickers Q . F . Gun , Mk II The 1 . 59 - inch Breech - Loading Vickers Q . F . Gun , Mk II was a British light artillery piece designed during World War I . Originally intended for use in trench warfare , it was instead tested for air - to - air and air - to - ground use by aircraft . Although it fired shells and had no capability to launch rocket s , it was widely but misleadingly known as the " Vickers - Crayford rocket gun . " Design . Vickers designed the gun early in World War I , intending it as a piece of light artillery for use by infantry in trench es in attacking machine gun positions and pillboxes . To make it portable for infantry use , it was very small and light for a gun of its calibre . Its light construction dictated a low muzzle velocity , which resulted in it having a short range . It was too light to withstand the detonation of standard British explosive propellants , so its ammunition used ballistite packed in cambric bags instead . The gun fired a 1 . 2 - pound ( 0 . 54 kg ) high - explosive shell at 800 feet ( 244 meters ) per second ; it also could fire an armour - piercing round at 1 , 000 feet ( 305 meters ) per second . The guns 40x79R cartridge was a shortened version of the naval 40x158R anti - aircraft cartridge , with the shell case reduced from 158 mm ( 6 . 22 inches ) to 79 mm ( 3 . 11 inches ) in length . The gun was , for ease of use in trenches , single shot ; the gunner had to extract the empty case of a fired cartridge manually and reload the gun after firing each round , which gave it a low rate of fire . It had a simple block breech with percussion gear , and was mounted on a non - recoiling frame consisting of a hydraulic buffer , trunnion block , and rear guide tube . Hand grips were mounted on the guide tube . The gun had a large muzzle brake to reduce recoil . Vickers manufactured the gun at its plant in Crayford , England . Operational history . The concept of using the 1 . 59 - inch Breech - Loading Vickers Q . F . Gun , Mk II in the trenches was superseded by that of the trench mortar , which was simpler , cheaper , easily portable , and more effective . With the gun no longer wanted in the trenches , it was decided to adapt it for use on aircraft as an air - to - air weapon against airship s and observation balloon s and for use against ground targets such as trains , ammunition dump s , and tank s . When mounted aboard aircraft , the gun could fire incendiary , armor - piercing , and high - explosive cartridges . The incendiary shell in flight emitted very hot flames from two openings in its base , which made it look as if the gun had fired a rocket ; this led to the guns misleading but widely used popular name of " Vickers - Crayford rocket gun . " The gun was approved for aircraft use in 1917 . For operational testing , it was fitted to F . E . 2b aircraft of Nos . 100 and 102 Squadrons , Royal Flying Corps , in April 1917 . The squadrons tested it on night operations and reported mixed results . No . 102 Squadrons Captain T . J . C . Martin , an F . E . 2b pilot , reported that his observer stopped a train after firing about 30 rounds at it , and that it took his observer 30 minutes to fire 50 aimed rounds ; he submitted an enthusiastic report on the gun and its potential . No . 100 Squadron , however , reported problems with the gun ; its report stated , " Sometimes the shell does not leave the barrel for some time after the striker has been released ; " in one incident , a gunner who thought the gun had misfired was about to open the breech to remove what he thought was a hung round when the shell went off in a shower of sparks . This led the squadron to require gunners to wait five minutes before removing a misfire . The gun also suffered from weak trigger springs and some of its shells had defective primers . It was hoped that the gun would prove useful in attacking German airships over the United Kingdom , mounted on British fighters so as to be able to fire upward into an airship flying above the fighter . Plans to mount the gun on the Parnall Scout fighter apparently did not come to fruition . At the request of the War Office , Vickers built a single prototype of the Vickers F . B . 25 two - seat night fighter to employ the gun , but the F . B . 25 failed official tests and crashed in May 1917 on the way to Martlesham Heath . The Royal Aircraft Factory N . E . 1 night fighter was also constructed to the same specification to carry the gun ; though it flew well , it lacked the performance for use as a night - fighter . After the failure of both the F . B . 25 and N . E . 1 to win production orders , interest in operational employment of the 1 . 59 - inch Breech - Loading Vickers Q . F . Gun , Mk II appears to have waned ; moreover , the introduction of an incendiary round for use in machine guns had made aerial use of the gun less desirable . The gun was withdrawn from use entirely , apparently by no later than the end of World War I .