Get a wsm. If your lucky you may find a 7 wsm like I did. If not get a 270 or 325 wsm for cheap and have it barreled. I picked up a used 270 wsm last year in a Montana for under $700.
The WSM action has an almost 3" mapbox. The barrel also has a little more shank so a wide shouldered round has enough meat around it. Hold a 284 case next to a 7-08 Montana shank and you'll see where some of the concern comes from on that thin contour.
My 7 wsm is factory and shoots great.
Bb
Lilja will duplicate the factory contour in 1:7 or 1:8 .284. Figure ~$850ish for a donor and $600-$700 for a bbl and threading/chambering and you've got a sub 8# all-up rifle with enough case capacity, magazine capacity, velocity, and bullet weight/variety to easily make a 1-rifle big-game do-all for $1,500 give or take.
