2 cm Flak 30 / 38 / Flakvierling The Flak 30 ( " Flugabwehrkanone 30 " ) and improved Flak 38 were 20 mm anti - aircraft gun s used by various German forces throughout World War II . It was not only the primary German light anti - aircraft gun , but by far the most numerously produced German artillery piece throughout the war . It was produced in a variety of models , notably the Flakvierling 38 which combined four Flaks 38 onto a single carriage . Development . The Germans fielded the unrelated early 2 cm Flak 28 just after World War I , but the Treaty of Versailles outlawed these weapons and they were sold to Switzerland . The original Flak 30 design was developed from the Solothurn ST - 5 as a project for the Kriegsmarine , which produced the 20 mm C / 30 . The gun fired the " Long Solothurn " , a 20 × 138 mm belted cartridge that had been developed for the ST - 5 and was one of the most powerful 20 mm rounds in existence . The C / 30 featured a barrel length of 65 caliber s , firing at a rate of about 120 rounds per minute . The C / 30 also proved to have feeding problems and would often jam . This was offset to some degree by its undersized magazine , which held only 20 rounds , which tended to make reloading a common requirement anyway . Nevertheless the C / 30 became the primary shipborne light AA weapon , and equipped a large variety of German ships . The C / 30 was also used experimentally as an aircraft weapon , notably on the Heinkel He 112 , where its high power allowed it to penetrate armored car s and the light tanks of the era during the Spanish Civil War . Rheinmetall then started an adaptation of the C / 30 for Army use , producing the 2 cm Flak 30 . Generally similar to the C / 30 , the main areas of development were the mount , which was fairly compact . Set - up could be accomplished by dropping the gun to the ground off its two - wheeled carriage and leveling with hand cranks . The result was a triangular base that allowed fire in all directions . The main problem with the design remained the fairly low rate of fire , which at 120 rpm was not particularly fast for a weapon of this caliber . Rheinmetall responded with the 2 cm Flak 38 , which was otherwise similar but increased the rate of fire to 220 rpm and slightly lowered overall weight to 420 kg . The Flak 38 was accepted as the standard Army gun in 1939 , and by the Kriegsmarine as the C / 38 . In order to provide airborne and mountain troops with AA capabilities , Mauser was contracted to produce a lighter version of the Flak 38 , which they introduced as the 2 cm Gebirgsflak 38 ( 2 cm GebFlak 38 ) . It featured a dramatically simplified mount using a tripod that raised the entire gun off the ground , which had the side - effect of allowing it to be set up on more uneven ground . These changes reduced the overall weight of the gun to a mere 276 . 0 kg . Production started in 1941 and entered service in 1942 . Ammunition . A wide variety of 20x138B ammunition was manufactured and used in 2 cm Flak weapons ; some of the more commonly used types of ammunition are listed on the following table . Other ammunition types that existed included numerous practise rounds ( marked " Übung " or " Üb " . in German notation ) , and a number of different AP types . A high - velocity " PzGr " 40 round with a tungsten carbide core in an aluminium body existed in 20x138B caliber . 2 cm Flakvierling 38 . Even as the Flak 30 was entering service , the Luftwaffe and Army had doubts about its effectiveness , given the ever - increasing speeds of low - altitude fighter - bomber s and attack aircraft . The Army in particular felt the proper solution was the introduction of the 37 mm caliber weapons they had been developing since the 1920s , which had a rate of fire about the same as the Flak 38 , but fired a round with almost eight times the weight . This not only made the rounds deadlier on impact , but their higher energy allowed them to travel to much longer distances , allowing the gun to engage targets at longer ranges . This meant it could keep enemy aircraft under fire over longer time spans . The 20 mm weapons had always had weak development perspectives , improving just enough to keep them useful . It was something of a surprise when Rheinmetall was able to " pull a fast one " again , introducing the 2 cm Flakvierling 38 , which improved the weapon just enough to make it competitive once again . The name " vierling " means literally " quadruplet " and refers to a four - barreled combination gun . The weapon consisted of quad - mounted 2 cm Flak 38 AA guns with collapsing seats , folding handles , and ammunition racks . The mount had a triangular base with a jack at each leg for leveling the gun . The tracker traversed and elevated the mount manually using two handwheels . The gun was fired by a set of two footpedals — each of which fired two diametrically opposite Flak 38s — and could be operated either automatically or semi - automatically . When raised , the weapon measured 307 cm ( 10 feet 1 inch ) high . Each of the four mounted guns had a separate magazine that held only 20 rounds . This meant that a maximum combined rate of fire of 1 , 400 rounds per minute was reduced practically to 800 rounds per minute for combat use – which would still require 10 magazine swaps per minute on each of the four guns . The guns could be fired in pairs ( diagonally opposite ) or simultaneously , in either semi - automatic or fully automatic mode . The effective vertical range was 2200 meters . It was also used just as effectively against ground targets as it was against low - flying aircraft . The gun was normally transported on a Sd . Ah . 52 trailer , and could be towed behind a variety of half - track s or trucks , such as the Opel Blitz , SdKfz 251 and SdKfz 11 . It was also mounted onto half - tracks and tank bodies to produce mobile anti - aircraft vehicles , such as the SdKfz 7 / 1 ( based on the SdKfz 7 half - track ) and the Wirbelwind and original Möbelwagen prototype ( both based on the Panzer IV tank ) . In Kriegsmarine use , it was fitted to U - boat s and ships to provide short - range anti - aircraft defense , and was also employed in fixed installations around ports , harbors and other strategic naval targets . The Flakvierling was also a common fixture on trains , even on Hitler ' s own command train , where pairs of them were mounted on either end of a " camelback " flatbed car and then covered to make it look like a boxcar , sometimes with a pair of such twin - " Flakvierling " mount cars for defense , one near each end of Hitler ' s " Führersonderzug " train . The closest equivalent fielded by any of the Allied nations to the " Flakvierling " gun system was the Browning M2 - based M45 Quadmount open turret unit , usually fitted as the main armament of the American M3 half track as the M16 Multiple Gun Motor Carriage .