So I am going off on a tangent a bit. What was wrong with The Aug, and other 5.56 rifles like HK 93, the FN and others? And a host of others from the 80's-90s.
The AUG soldiers on and has been upgraded. I wanna say the Australia, New Zealand, and Ireland (and Austria of course)use it as their service weapon and are generally pretty happy with it.
The H&K G33 is reliable, but it's a heavy, unweildy and not real great for adapting to the modern things you want on an assault rifle...it would quickly become a boat anchor. The G33 was really kind of a stop gap rifle, it was just making a G3 into a 5.56 and it was never ideal.
The FNC is a great rifle and has served the Belgians well, but it too is a bit on the heavy side and not the best for adding accessories and modernization. The Belgians will be dumping the FNC and replacing it with the SCAR in the near future.
