Caliber: 9x19mm Luger/Para
Weight: 4,7 kg loaded, 4,03 kg empty
Length (stock closed/open): 630/833 mm
Barrel length: mm
Rate of fire: 500 rounds per minute
Magazine capacity: 32 rounds
Effective range: ca. 100 meters

The M.P. 38 submachine gun started its life 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 serveup 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.