Re: How does cold affect your barrel?
I do a great deal of shooting in both 60-80 degree air as well as sub zero air close to sea level. If my ammo is kept in a warm truck around 70 degrees I dont notice a zero or accuracy change out to 300 yards. 400-600 is small and after 600 yards its time to really compensate for the thick air. I only use McMillan stocks to minimize the cold air's effect on my rifle. I am VERY lucky to have a 308 that will not throw bullet #1 out of the group due to the "cold bore" shot. Even if the barrel has been in -10 degrees for quite some time. This is of course if I am using warm ammo. If your ammo is going to get that cold, its best to develop a load for your hunt in those conditions. Personaly I tend to keep ammo in my pocket and load the rifle when I am setting up for the shot.
Some key points to think about in cold air shooting:
Use a GOOD synthetic stock free floated.
Keep the barrel to 26" or less. including brakes.
Keep your ammo warm or develop for the enviornment and/or use only EXTREEM powders or learn in detail what happens to you velocity at various temps, then compensate for your POI and trajectory accordingly.
If your rifle has a cold bore issue, concider a warm up shot followed by the killing shot. You will not need to use this practice up to 300 yards unless you have a real turd of a rifle.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.