Oldelk,
AC is right, I had a 300WM Montana and it performed very well. As you may know, it is about a bit longer and heavier than the 300WSM. You can look at the stats. The 300WM delivered about 100fps more than my 300WSM's have so that is really of no consequence. I think the 300WSM Montana is a more efficient package. The maximum magazine length, according to my notes was 3.405" which allowed plenty of room for "tweaking" your OAL's.
I also had the same package in a .338WM. After all my playing around, I feel the 300WSM is the best package for what I need done while saving about 12 ounces in the process.
Good luck with your decision.
