When camping in cold weather, I always leave my rifle where it stays cold- I don't have any condensation issues that way. About 10+ years ago I was on a deer hunt in Montana with Muledeer. We were staying in motels and bringing the rifles in every night. A week went by and I tried to shoot a buck. My rifle went "click", twice. I had to use his spare at that point (an ULA in 257Imp).
When I got home, I found that the interior of the bolt was rusted, cushioning the firing pin which didn't fall hard enough!
That was an eye opener...
++1!
Taking equipment from cold into warm is harder on it than leaving it out in the rain IMO. Moisture condenses on the cold metal, inside every part. Going from dry cold to warm moist air is also a severe test of waterpoofing on optics.
We leave rifles outside in the cold if possible, under some kind of rain shelter if it is raining: porch, big tree or plastic bag as long as the plastic is above the rifle and not clinging. If not possible, I have taken a hair drier and warmed and dried the rifle and action thoroughly in a motel room. At least open the action, remove muzzle tape, dry, and wipe down till the piece is warm, dry and no longer condensing moisture.
Getting in and out of a warm pick-up in cold weather produces condensation each time you get in the rig with the rifle. I don't have a good solution but I keep windows open if I can stand it for short stays in the rig, or try to warm the piece slowly, then put it right in front of a blast of warm dry heater air to dry out the action inside.
I've had ice form from water inside the bolt that has caused misfires on two rifles. One was a Rem 700 on a bull elk at dawn. It had rained the afternoon before and I'd wiped down my rifle and left it outside the tent as usual, where it froze hard overnight. At the break of the sear there was a soft "chiiink". I knew what had happened. I ejected the cartridge as quietly as possible in the morning fog and saw a small dimple in the primer. I hoped that the firing pin had broken enough ice to fall harder on the next try. It did and the rifle fired. Hidden behind a big log I was resting over, the bull hadn't noticed me in the sound-dampening fog at 100 yards. Lucky. The other one was on a coyote with a 22-250 in a 788.
