I have Kimber 8400's in all three of the WSM's. Hopefully I can start on the Montana's next year. My three rifles have the following personalities:
The 270 WSM is the most accurate i.e. 1/2 to 3/4" 3 shot groups at 200yds.
The 7 WSM is driving me nuts because I haven't yet found a handload that shoots better than Federal 160gr Accubonds (at 3120fps). I shot Sunday and out of a cleaned bore the first 2 shots were less than 1/2" the third opened it up to a little over an inch. This rifle always dead centers the first 2 shots at 200yds from a cleaned bore - I'm taking it Elk hunting next weekend.
The 300 WSM hasn't yet shot as well. Some 1 to 1 1/2 200yd groups. I may have been trying to make loads that have worked well in my other 300 WSM's work in it too much instead of trying to find what it likes. So far it's my least favorite of the three - but I have a Sako Finnlite in 300WSM that's also going on the Elk hunt for days I may be walking in rain or snow......
-Federal loads the 180 Accubond in the 300 WSM and the 160 Accubond in the 7 WSM. At 300yds and out the 7 WSM has more energy than the 300.
So in conclusion:
-If you don't handload definitely buy the 300 WSM, it's far the most popular
-If you want the most efficient ballistically buy the 7 WSM.
-If you want the most accurate and easiest to shoot buy a 270 WSM
The 7 WSM in a Montana might be pretty hard to find.
