Ten of each weapon; 6,000 rounds per weapon; 120 rounds fired per "dust cycle" (and when they say dust, they mean DUST...testers had to wear respirators and Tyvec suits); wiped and light lube every 600 rounds, fully cleaned and lubed every 1,200 rounds.
XM8: 127 Class I, II and III stoppages.
Mk16 (5.56 SCAR): 226 Class I, II and III stoppages.
HK 416: 233 Class I, II, and III stoppages.
M4: 882 Class I, II and III stoppages.
Thus, in this extreme dust environment, XM8 firearms failed 2% of the time, while the current weapon of the U.S. military, the M4 failed about 14% of the time.
The Army could care less, despite the fact that it conducted the tests.
I have never pretended to be an expert on small arms. But, it is hardly surprising that it is possible with 21st century technology to make a small arm that is better than a Vietnam War era firearm.
Small arms cost a pittance, compared to other major military systems, and small arms are far more important to the U.S. military effort on a day to day basis than many other expensive major weapons systems that the military is currently in the process of procuring.