Garand Thumb did an unscientific test on the functionality of frozen rifles. I stress unscientific because it seemed to me that the way he froze the rifles, coupled with various rifle designs (indents, etc. on receivers) as well as how the rifles were placed for freezing might have affected how different parts of each rifle froze. Then again, if you were to leave your rifle lying out in the snow, it's probably somewhat haphazardly and randomly laying in the snow.
He did three stages. Firing all the rifles at I think 25deg, then splashing water on all of them and letting that freeze and firing again, then dousing the rifles with water, letting them freeze, and testing again. In the end, the AKs and FALs apparently came out the winners. The Galil did okay as well. It was kind of educational to see just what was freezing up on each rifle to prevent them from functioning. By the third test, on almost everything without a big ass AK style safety, the first thing out the gate was trying to even get the safety from safe to fire.
You can probably skip the first ten minutes. Firing the rifles dry in 25deg, all but one - a milspec AR build - functioned flawlessly. He specifically said that the failed AR was one that he had purposely let go for a long while with no cleaning, so maybe some gunk hardened up.
https://youtu.be/LbjpIP5ShH0