My hunting ar, lightly lubed bcg with wolf head sae 30 got pretty gummed up feeling this winter on a frigid -15 degree morning. I did not shoot it, I know I should have tested it, but when I went to cycle it to remove the chambered round before transport it was very sluggish and gummed up.
Now, if I plan on hunting in the cold I go out with a bone dry rifle and lube up before I put it back in the safe
Next winter I will run some reliability tests by leaving a lubed gun out all night.
I've heard they use dry lubes in cold places like Alaska. I'd like to find some of that stuff.
From an article I read on here, the only semi auto rifle to pass Alaska state trooper test trials was the galil
Tests included frozen rifles if I remember correctly
Eta, a 0w-20 oughta perform fine. I think straight thirty is nice in warm weather to keep oil in place but too vicious for cold start (cold shot) in sub zero