As far as I remember it wasn't a very successful rifle. The cartridge was too powerful to shoot short bursts like STG would and the gun had no bipod to be used like a BAR. In effect the only point of using full auto was fighting in close quarters. Such characteristics, when transformed into coh2 weapon model would mean very short burst at long to mid range, effectively equal to SVT and big dps increase at short range that would overlap with SMGs. It doesn't sound great, does it?
Btw. honestly, we don't really need assault rifle on every faction. And SVT troops definitely give soviet forces enough mid range oriented firepower.
Look at how pretty controllable the AVT-40 is in short bursts, even the full automaton has a return strictly backward. And M14 - which jumps like a mad bull.
Also about the AVT, the soldiers demanded that they be sent more AVT to the front, the SVTs altered in AVT in the front-line masters. And therefore, from 1943 until 1945, SVT was produced only as AVT. The soldiers liked the automatic fire in critical situations.
For AVT produced 15-cartridge magazine. Like this soldier of the Czechoslovakian corpus:
In 1944, when Tokarev modernized the SVT-40, a reliable 20-cartridge magazine for SVT was developed. Improved SVT was not produced (because in 1943 the military focused entirely on weapons for an intermediate cartridge), but the 20-cartridge magazine was issued in small batches and used on the front.