Bad gas system from the go using the crap direct inpingment sytem. The HK 416 is the stuff. Have owned several 'civilian' inpingment systems. Nothing innovative about them any longer. U.S. is long over due for a nice system for all conditions.
Here is bit of info: 1/5 of all the small arms in the world are an AK variant. Reason? A superbly reliable weapon system that will function under the most extreme conditions with the design nature knowing soldiers need a weapon to shoot - not clean.
"Well, I thought it was a rabbit but it turned out to be Bear Grylls in a rabbit hide."