Let’s make it clear: we never said that the AR platform wouldn't work at negative temperatures. But there's an inherent problem with the AR platform that affected its functioning under certain environmental conditions. In particular, icing can cause a failure of the weapon's operating parts. This can happen at near-zero temperatures, under alternating rain/snowfall, in the mountains, or during air or sea landing.
Gun Myths: AK vs. AR. Icing
One more icing test, but this time with better visual evidence