Re: .300 WSM or .300 Win Mag
Personally I would strongly consider the .300 Win mag for a few reasons. First of all, I have had very good luck with this caliber. Deer, elk, moose and black beer all taken with this caliber, over 30 animals total... not a one wandering off wounded. Many kills over 500 yrds, still has the energy to do it. Longest shot was a moose at 830 yrds and just killed an elk this week at 643 yrds, one shot.The 300WSM would probably give you similar if not identical results... so on to a couple other reasons.
Second, reloading data is more widely available for the standard .300 Win Mag, especially if you or your buddies have older manuals.
Third, availability of factory ammo. Enough said... you just went through the nation wide ammo shortage like the rest of us. It is a "military round" which also opens up the availability of "surplus ammo" for target shooting or emergencies.
Finally, if you reload, the brass can be found cheaper and more abundantly.
Hope this opinion helps. Have a couple buddies who really like their .300WSM rifles as well.
Either way, if you reload, try the .30 cal Berger 190 vlds out. I just shot a three shot group of these reloads at 500 yrds... 2.5 inches minus! That was out of my "stock" Remington 700 Sendero. The elk I just shot this week was my first kill with one of these guys. At 643 yrds it took out the lower lungs and busted both front legs almost clean off