Re: .264 Win Mag for Elk
IMHO the 264 using 140's is big enough for elk. The only thing I would do differently at the 264 win mag velocities would be to use a stouter bullet for elk such as the ACCUBOND or similar.
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.