Pál Király Pál Király ( 1880 – 1965 ) is an Hungarian engineer and weapons designer . Work & designs . Király ' s career as weapon designer had is beginnings in Switzerland , where he emigrated after WW1 . One of his designs was called the Kiraly - Waffen . In the 1920s he developed the SIG KE and the SIG Kf . 7 Machine Guns , and the SIG MKMO machine - carbine . The MKMO ( and its shortened variant , MKPO ) was successfully sold to various countries in 7 . 63 & 9mm Mauser and 7 . 65 & 9mm Parabellum chamberings . In 1929 Király designed an advanced 9x19mm pistol , designated as ' KD Danuvia ' . 20 guns were manufactured for trials . Among others , Germany was very interested in this pistol , but the 1929 - 33 market crash put a hold on new developments worldwide . Interestingly , the later Walther P . 38 displays extreme ' similarities ' with the KD Danuvia . The two guns internally are the same , outside differences were the P . 38 ' s distinctive grips and a shorter barrel . Király most significant development is the lever - delayed blowback workiing principle , successfully applied in many of his designs , like the machine carbines Danuvia 39 . M and Danuvia 43 . M , and used in the French FAMAS assault rifle . In 1932 Király designed a self - loading ( automatic rifle ) , which was the first automatic rifle in the world utilizing a muzzle brake . ( The more famous Simonov Model 1936 featured the first muzzle brake outside Hungary , 4 years later ) . The Király rifle was very well balanced , it weighed less than 4 kg [ 8 . 8 lbs ] . It had a well sealed dustproof operating mechanism , came with a small 10 - round box magazine . In 1933 Király introduced a larger version of his 1932 automatic rifle . This gun weight 6 . 5 kg [ 14 . 3 lbs ] , had heavier , longer barrel , a large 80 - round magazine and a muzzle brake . On 7 / 11 / 34 the Italians reviewed Danuvia ' s available arsenal , showed interest , but eventually decided to stay with their own weapons . ( Except for the 12 . 7mm Gebauer GKM ' s , to which the Italians had no equal . ) In 1939 the Honvédség adopted Király ' s Machine - Carbine with the Danuvia 39 . M designation . A modernized version was adopted in 1943 under the Danuvia 43 . M designation . His last Hungarian design , designated Danuvia 44 . M was not adopted due to the Soviet invasion of Hungary . His 44 . M design was the basis of the Hungarian Kucher K1 Machine Pistol in 1951 . He designed the Danuvia 39M and improved it into the Danuvia 43M Submachine gun . After he moved to the Dominican republic , he designed the . 30 Kiraly - Cristobal carbine , which was essentially a copy of his earlier work , specifically the 44M ( an improved 43M ) . He made two more Cristobal carbine versions , the delayed blowback M2 ( Cristobal Automatic Carbine ) in . 30 Carbine and the gas - operated M3 in 7 . 62x51mm NATO . He patented the latter in 1961 as a competitor to the Belgian FN FAL . His . 30 Carbine M2 model was manufactured in about 200 , 000 exemplars between 1950 and 1966 , and " it remained in service until the late 1980s or early 1990s " . Although a semi - automatic weapon , its design was " more akin to submachine guns such as the Beretta Model 38 and the Hungarian 39M . " Personal life . Pál Dedai Király ( 1880 – 1965 ) was born in Budapest , Hungary , earned his degree in Machine Design at the Technical university of Budapest in 1902 . He became a Professor ' s Assistant at the University . He also earned a Military Reservist degree with an Artillery Lieutenant rank . During WW1 he served in the military 1914 - 18 and reached a rank of Artillery Captain . In 1915 he wrote his first publication about automatic weapons . After WW1 Hungary was prohibited from weapon development , so he moved to Switzerland and worked for SIG Neuhausen . From 1928 weapon development was again allowed in Hungary , so Király started to develop automatic weapons for Hungary . SIG refused to release some of Király ' s research to Hungary as they originally agreed , so Király moved back to Hungary to work with the Danuvia Rt , but he still worked for SIG under contracts in the 1930s . During 1929 - 44 he was paid from the Danuvia Factory ' s profit sharings . In 1945 Király escaped to Switzerland before the Soviets came . In 1947 he moved to the Dominican Republic , where he was employed by the Armeria of San Cristóbal , ran by a fellow Hungarian , Sándor Kovács . Király developed several weapons here , the most successful was his Cristóbal Carbine , of which a 1 / 4 million was sold . His last design was adopted in 1962 , when he was 82 .