I have to argue with you about some of that CD.
The M 1/ M2 carbines built a good reputation in any reasonable climate, both during WWII and in Vietnam, according to my Dad, who got there about 4 months after Chosin, the carbines worked fine in the summer, but in the winter, if you went into a heated bunker you had to leave your carbine outside or condensation would form on the steel , when you took it back out side it would freeze up.
The other weapons had more power and heavier parts so they were less prone to jamming from this.
But they all had to be run un-lubed in winter.