The MP40 is descended from the MP38, the differences being in cost-saving alterations, especially the use of more pressed rather than machined parts and an improved safety. The changes resulted from experiences with the several thousand MP38s, (in service since 1939), used during the Invasion of Poland. The changes were incorporated into an intermediate version (MP38/40), and then used in the initial MP40 production version. Just over 1 million would be made of all versions in the course of the war.
The designer of the MP38/40 was Heinrich Vollmer.
The MP40 was often called the Schmeisser by the Allies, after weapons designer Hugo Schmeisser. Although the name was evocative, Hugo Schmeisser himself did not design the MP40, but helped with the design of the MP41, which was effectively a MP40 with an old-fashioned wooden rifle stock, and the Sturmgewehr 44. Also, Schmeisser did not work for Erma, but for Haenel.
An MP38 can be easily distinguished from an MP40 by a round hole in the magazine housing, and a series of small grooves along the length of the steel machined receiver. The initial production MP40 had a smooth side on the magazine receiver, the main production was actually the MP40/I which had small indented grooves on the magazine side to strengthen it. The MP40/II was the experimental 64 round variant. There is some variation in modern sources with naming of the variant numbers.
The design actually used a similar amount of stamped sheet metal parts for its day as some other weapons, but is unique in that had a folding metal stock with plastic furniture rather than wood stock. The gun was quite reliable and rather cheap to make, as its parts were machine stamped. It had relatively low recoil even fired fully automatic. This is due to its slower rate of fire. Nevertheless, it gave the weapon a good accuracy compared to the American Thompson submachine gun.
The weapons magazine spring however were found to wear out very quickly, and cause jams if loaded fully with 32 rounds so they were nearly always loaded with 1-2 rounds left out, giving a capacity of 30. At one point a double magazine MP40/II was also experimented with 64 round capacity, with the double magazine being slid horizontally to use one magazine and then the next.
The MP40 had an overall length of 833 mm, though its folding stock could allow the weapon to shorten to 630 mm. The odd 'spur' near the end of the barrel was designed to allow the troops to hook the MP40 onto the firing ports of armoured personnel carriers, such as the Sdkfz 251 half-track.
Variants and developments Edit
- MP40/I - main production version
- MP40/II - experiment with a 64 round magazine.
- MP41: Technically different from the MP40 even though it looked similar. A wooden stocked weapon used by police units.
In the 1930s, its precursor weapon was developed. Though it was informally known as EMP 36, it was a factory prototype, not a deployed military weapon.