Have you consider swapping bottom metal and going to an aics 300WM 3.715 mag? Some people hate mags but it is a nice option if you wish to increase length.I would try and make sure you have enough magazine length to load heavy bullets far enough out in the case. In my dads 300 win mag I have to stuff the big bullets deep to fit mag length. I wish I had a longer magazine to seat them farther out so I could take advantage of more case capacity.
I am becoming a believer in Seekins rings too.