The PPSH 41 was a submachine gun designed by George Shpagin for the Russian military during WWII. This was a classic Soviet design infused with the user in mind. The user is likely to be illiterate and poor and not necessarily someone who has even worked around machine industries. It was made of stamped metal, easily taken apart and reassembled, and it worked under conditions of extreme cold in the arctic Russian landscape.
Six million PPsh-41s were manufactured during the Second World War. Germans liked them as well and often picked them up and fought with them. The Germans also probably appreciated the ability of the weapon to fire in the cold. The MP-40s Germans brought with them used German machine oils that couldn’t operate in minus 30 degrees. They fired a 7.62mm round from either a Mosin Nagant or a Mauser 98K. During the Korean War, Americans came up against them. In large formations they gave infantry the ability to put an impenetrable wall of lead.
Source: Photo: Nick’s Blog, Wiki