During World War Two, both German and Russian soldiers often thought that the other side's weapons were better than their own. In particular, both sides often preferred their opponents' SMGs. In late 1941, a group of German officers formally requested that Germany simply copy and produce the PPSh-41. This led to the HWA formally studying the question of PPSh-41 vs MP-40...and they found that the German gun was better, but the Russian magazine was better.

Naturally, as a result of this finding, the German military chose to convert captured Russian PPSh-41s to use MP-40 magazines . The conversion used standard MP40 magazines, and required magazine well adapters and new 9mm barrels. Some 10,000 such conversions were made in total. Some used cast magwell adapters and some were stamped, and the barrels were made from standard MP40 barrels turned down to fit PPSh trunnions.

The standard 7.62mm PPSh-41 in German service was designated MP-717(r), while the ones changed to 9x19mm like this were designated MP-41(r). Many thanks to Limex for giving me access to film this one for you!