H&K G3 market in East Africa

[M-A Lagrange]

Hello,

H&K G3, the former basic german army assault riffle is more and more popular in East Africa. At least from what I see on the field. Few years ago it was not the case.
Now comes my question:
Most of the combattants in South Sudan have AK47. Former SAF (Sudan Armed Forces, Khartoum army) were having G3 guns. So now, many former SAF supporters or people living close to past SAF opositions are having G3.
But from what I understood, G3 and AK47 ammunitions are not compatibles.
AK47 use 762x39 bullets and G3 762x51 bullets.
So my question is double:
1) Is it possible to use AK47 ammunitions with G3? If yes or no, why?
2) If no, that would mean you need a separate supply source for G3 ammunitions. As I am in South Sudan, where those ammunitions could come from.
For info, I already have with me the Small Arms Survey reports and othyer NGO reports on South Sudan weapons smuggling. But they do not cover the most recent years (2007-2010).

Thanks for your support.

M-A