As the Germans retreated toward Berlin, special squads of machine gunners equipped with MG34's and 42's were created on the spot to set up ambushes against the advancing Soviet military. Field reports claim they were successful where used. The German Army nonetheless had to keep falling back against numerical superiority.
The Russians had more soldiers, vastly more artillery, more tanks, more aircraft, and were finally being led by experienced ground commanders who could respond to attack and plan counterattack. What's missing from many of these discussions is a view that the forces at the commanders disposal aren't just soldiers with guns, but an orchestra of crew served weapons, and a large train of supplies feeding them. Changing just one weapon in the soldiers hands doesn't really affect the overall effectiveness. In fact, as the comment on British weapons points out, you can fight with weapons that are technically and tactically inferior - and win. HOW you fight with what you have is far more important that what you fight with.
To put it in different terms, "If the Soviets had AK's" could be compared to "If the Confederates had lever actions." What then? Ammo shortages. Neither had the ammo production capability for a exponential increase in ammo supply. As said, the Soviets already had problems early on with having enough guns at all. American Lend Lease didn't fill in all the gap, and Soviet industrial capacity was pretty weak to begin with.
The result of Ak's coming into the fray a few years earlier would have meant the Germans shifting production away from the bolt actions they still produced in increasing numbers right up to the end of the war. It took occupying the ground to stop it. Bombs couldn't.
Lincoln dealt with the same problem, a desire to move to the lever action and a military who wouldn't. We always seem to put down the decision makers who won't accept newer firearms, but the issue remains whether it actually adds a great deal of effective power on the battleground. Often not - it's really just an incremental increase, and the other 80% of the army in the field isn't helped at all. They don't use a rifle as their primary tool. They drive, type, and input coordinates. You could give them 5 pound full auto guns with 250 round mags in a .308 equivalent power level, and they would still just qualify with it more than shoot it in self defense.
Individuals focus on their weapon, generals focus on their systems. You win a war because your system was more effective than the opposition.
