Not this again!
Federov designed a select fire, magazine fed rifle using a reduced power cartridge (6.5mm Japanese v. the 7.62x54R) in 1916. It worked, but wasn't totally successful.
The Germans really refined the Assault Rifle concept into what it is today. Other than the overall layout, there are no functional similarities between the Stg and the AK47. The Stg uses a falling block locking mechanism v. the rotating bolt of the AK. Stg has a hinged receiver, AK has a dust cover. Stg has a recoil spring in the butt, AK locates it above the bolt carrier. Stg removes the butt for stripping, AK the dust cover. Stg has separate selector and safety switches. AK has a single lever. Stg has a button mag release, AK a lever. Absolutely none of the mechanics are even close between the two. You'd think that Mikhail would have used something if he "copied" the Stg.
As was stated previously, the SKS is a scaled down, modified version of an earlier 14.5mm anti-tank rifle. Not a copy of anything from the Stg.
The German M43 7.92x33mm cartridge was adopted in 1943. Design work began in 1938 I believe. The Soviet M43 7.62x39mm cartridge was adopted in 1943 and design work began in 1939. There were Soviet spies in Germany at the time and the concept may have been stolen by the Russians and started their work to the M43. Don't really know that one. However, don't lay it at Kalashnikov's feet as he simply designed a weapon around the cartridge he was given.