Regarding bin Ladens's AKS-74U, the rumor that is put out by his boys is that he took it off a fallen Russian general. But the closer reality is that it was picked-up by a member of the Mujahadeen off a fallen Russian soldier and presented to him as a war trophy later. That's what the guys that used to run with him back in the day said about it, anyway.
And that side-folding AKM he's firing used to eat on me as far as identifying it until I was doing some reference on another firearm and happened upon a photo of a Russian soldier in the field with one (looked to be circa. 1980's). It looked to be some kind of prepared photo showing it as a prototype in the field. I usually save all my photos for reference myself but naturally that was one of those days where I couldn't save it on anything. I will try to dig it up again for everyone.