MP - 40 The MP40 ( Maschinenpistole 40 - Submachine Gun 40 ) was a submachinegun developed and used by Nazi Germany during WWII . Description . The MP - 40 submachine gun started its life as MP - 38 . Under requirements from German " Heereswaffenamt " ( " HWA " , Army Weapons Office ) , which saw the need for a compact submachine gun , suitable for use by armored vehicles crews and paratroopers . German arms - making company " Erfurter Maschinenfabrik Gmbh " , better known under its trade name " Erma " , began the development of a new weapon under HWA specifications . It must be noted that a new submachine gun was not built from the scratch ; instead , it was just an evolution of a rarely known prototype weapon , provisionally known as Erma MP - 36 . MP - 36 was a compact version of the better known Erma EMP submachine gun , but fitted with now - familiar underfolding metallic shoulder stock and bottom - feed magazine , which was slightly canted forward to accommodate EMP magazines . MP - 36 was a selective - fired weapon , and in fact the improved MP - 38 was a simplified version of its little known predecessor , adapted for different magazine . Therefore , it took only few months before the new weapon was ready for official adoption and mass production . Manufacture of a new submachine gun , designated as MP - 38 , commenced in summer of 1938 , at Erma , and later on also at C . G . Haenel . The gun was manufactured for just 2 years , when it was replaced in production by externally similar , but less expensive MP - 40 , which used more stamped parts instead of machined parts , found in MP - 38 . There also were minor variations in design of MP - 38 , such as shape of cocking handle etc . MP - 40 was also produced in a number of variations , which differed in shape of certain parts ; also , toward the end of the war , several production shortcuts were introduced to save the costs of manufacturing . probably the most interesting variation of the MP - 40 were the MP - 40 - II and MP - 40 - II . These guns featured dual magazine housings which hold two magazines in a laterally sliding bracket . This increase the total ammunition capacity " in the gun " to 64 rounds , in a desperate attempt to catch up with 71 - round magazine capacity of Soviet PPSh - 41 . The later variant , MP - 40 - II , was made in limited numbers , but turned out to be a failure - sliding dual - magazine housing was a constant source of jams and failures , and was very sensitive to dirt and fouling . Nevertheless , MP - 38 and especially MP - 40 submachine guns were of good design , and set the pattern for so called " second generation " of submachine guns ( " first generation " being represented by the wood - stocked and carefully machined MP - 18 , MP - 28 and the like ) . The second generation weapons usually were of compact design , and made using mostly steel stampings and pressings , or castings . It also must be noted that many MP - 40 that survived the WW2 , continued to serve up until late 1970s or early 1980s , in few European armies such as Austrian or Norwegian . Both MP - 38 and MP - 40 submachine guns are blowback operated weapons that fired from open bolt . Both weapons were full - automatic only , but relatively slow rate of fire permitted for single shots with short trigger pulls . The proprietary bolt system with telescoped return spring guide served as a pneumatic recoil buffer , helping to decrease rate of fire to a very manageable level . The bolt handle was permanently attached to the bolt on early MP - 38 ' s ; on late production MP - 38 ' s and MP - 40 ' s bolt handle was made as a separate part and also served as a safety - pushing the head of bolt handle inward locked the bolt either in cocked or forward position . Lack of such feature on early MP - 38 ' s resulted in field expedients such as leather harnesses with small loop , used to hold the bolt in forward position . One unusual feature on most MP - 38 and MP - 40 submachine guns was an aluminum or plastic rail under the barrel , which served as a barrel support / protector when firing over the board of armored personnel carrier . The short handguard was made from plastic and was located between magazine housing and pistol grip ; barrel lacked any heat insulation , which often caused burns for supporting hand . Folding shoulder stock resulted for compact weapon when folded , but it was insufficiently durable for combat use and hand - to - hand combat . Single - feed , double - row box magazine was another weak point of the design ; it was hard to load without additional help , and often caused jams .