41 submachine gun originally  chambered for 7.62x25 Tokarev, a round the Germans did not  (officially) use. But the 41 was easily rebarrelled for 9 millimeter  parabellum round, which the Germans did use, and the weapon was, in  fact, adopted by the Germans as the MP717(r). While the drum  magazine worked with 9mm ammo, the Russian curved stick magazine did  not. If the Germans chose to use stick magazines with this gun, they  had to modify the magazine housing to accept German issue MP38/40  magazines. However, doing this would prevent the use of the drum  magazines. So Steiners weapon, therefore, may be in the original  caliber, or may have been rebarrelled for 9mm parabellum, but had  not been modified for German stick magazines.