Simoninsky, or however it is spelled in Roman letters, worked on Semi Autos between the wars just like other nations. Like the others, except Garand, he discovered that full power rounds beat the actions to death. His first successful rifle used the 6.5x50 SR Japanese Military loading. The Russian authorities wanted a bigger bullet, hence the 7.62x39. The Germans picked up on that too, and developed the 7.92 Kurtz for thier true assault rifle, the GW 43, adopted in 43. If you say the SKS was used about the same time. I'll take your word for it.