I always wondered if they were just trying to piggyback on American R&D on the cheap.
I can remember when the Soviets used to design American vacuum tubes into their radar equipment. The tube identifications were right there in the specifications.
In a lot of ways, the AK-74 is a nice weapon.
It has less recoil than the AK-47, probably similar reliability. The bullet turns sideways (nearly all rifle bullets pitch or yaw on hitting flesh) but doesn’t usually fragment.
It doesn’t have the accuracy of the M-16 in rapid fire. Moving pistons jostle the line of sight, so to compensate, Russia teaches soldiers to shoot two or three bullets. That isn’t a half bad approach, especially with an enemy that uses camouflage to disguise exact position.
The bottleneck 39mm case is a bit more efficient than the straighter 45mm case of the 5.56x45 M-16, but that doesnit matter much because powder is cheap and light. The difference between them doesn’t drive either flash or recoil.
The point of the smaller bullet is you don’t just shoot at your known enemy, you shoot at where he is, or where he might be. That can suppress him even if he is hidden, and give your side fire superiority (many going his way, fewer going yours). Then your side can maneuver to his flanks and rear, and when he realizes it, the enemy can psychologically break: freeze or try to run away. Either way you will big.
Combine that with thermal goggles so you can see him very well and you have a big advantage. The Soviet Union was very very effective in 1945, and would have been a tough adversary up until its final days. Russia would still be a very tough adversary, though their best units are far smaller than they used to be. (so are ours!)