Re: upgrade to .300wm or .338wm?
The .338 is larger, sure, but it has a considerable amount more recoil than a .300 WM and is a good bit more expensive to shoot. I've got a Remmy XCR in .300 WM and love the thing. Recoil is very manageable when shooting 20+ times in a day and my XCR is extremely accurate for a stock hunting rig. Off a bench with bipod (no sand bags) it will shoot 1/2 moa all day @ 100yds. It will hold 1 moa with no worries out to around 450yds as well. I have an .06 as well, however you will notice the difference in performance at longer distances with a .300 and it has a lot more wallop at closer ranges when loaded with heavier hunting rounds. The .300 is plenty for any game animal on this continent, although a brown bear would be more worthy of a .338. My opinion, go for the .300 WM and you won't be dissapointed. If you feel that for some reason you have outgrown it, upgrade to the .338 mag.
Chad