Re: 7mm mag vs. 300 win mag
If it were me I would go 300, but thats just me. This choice is going to come down to personal preferance.
Youre going to get about 3100 FPS from a 160-162 grain bullet in 7mm RM. Youre going to get about the same velocity from the 300 WM with a 190 grain bullet. So, what do you want?...In my opinion, the accuracy POTENTIAL (please note: emphasis on potential) could be better for the 300 as well as slightly better barrel life. Go with the one that makes you the most happy. I also feel there is a better selection of bullets for the 30 cal. 110-240 grains in any configuration you like.
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.