The AK is not an StG copy!
The concept is the same.
A rough history of Assault Rifles:
Cei-Rigotti = Italian, turn of Century, 6.5mm full power, gas-operated, 25 round box mag, 900rpm, innacurate, not adopted.
Fedorov Avtomat = Russian, 1916, 6.5mm intermediate round (later converted to Jap Arisaka full-power), gas-operated, versions similar to AKSU RPK, used in WW1 and Red Revolution - but not adopted.
MKb42/MP43/MP44/StG44 = German, 1942-45, 7.92 intermediate round (KurzPatrone), gas-operated, adopted at squad-section level and intended to replace SMG's LMG's and Rifles, too little too late.
AK47 = Russian, 1949-present, 7.62 intermediate round, gas-operated, adopted by Soviets and just about everyone else!
Borrowed feaures from PPK44 and M1 Garand, but not StG44 as everyone thinks (but was influenced by it and the MP40 Schmeisser).
Hugo Schmeisser more or less directly responsible for AKM and AK47S/AKMS upgrades.