OKW get inf-stg-44's
Yet sov cant get avt-40 
Well historically, Stavka determined the AVT's combat performance was "less than that of a submachine gun" (their actual words, full quote is
When converting a semi-automatic rifle to fully automatic by only modifying the trigger group, its combat usefulness decreases to less than that of a submachine gun. ). So unless you want a gun that's worst than the PPSh's. Better off with PPSh's
Even if they ignored the accuracy / recoil problem, it's still a rifle that spits out it's 10-round magazine in about a second, so taking into account the SVT's reload time of 2-3.5, you'll have them spend more time reloading than shooting!