As I reluctantly recall from my Sub-Saharan days, it was more the SA ammo than the weapon. I also seem to recall the FN having a heavier barrel. Perhaps I got that Sierra backwards :o
Valid point going back to the Sergeant Major's link to the Small Arms Survey. The head stamp will identify the manufacturer's country of origin, but the packaging will identify many other things such as the original destination. Either way you are in for a ton of investigative work.
My best guess still resides with Kenya - Their historic love for the G3 (during that period of time twice as expensive as the AK) together with cheap and easy access to 7.62 NATO :D