Re: 308 and 300wsm
The bullets for each are the same size. 30 caliber or 0.308" The cases are the same length but the 300 wsm is much fatter. Reloading is very different. As a general rule you will use slower powders and much more of it for the 300 wsm.
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.