I am not sure how well it would stabilize the heavier 180 Berger.
I think there are few factory 7MMRM with the 1x9 or faster twist for the heavier bullets made as MFG rifles. My Weatherby Vanguard 7MMRM is a 9 1/4 twist and did fire 175 Nosler partitions well.
Its all about budget..good consistent long range shooting rifles need some work typically, trigger and range time to get confident and consistent down range, whatever you purchase and work on.
Such things as action bedding, rifle fit to person, trigger adjustment or replacement, upgrades and such are a few possibilities. Get it all done prior to loading because some of this work my cause you to make loads differently...and can effect point of impact down range.
Other things to consider are what the rifles ultimate use is for. this can guide you to weight of rifle you desire and many other choices to be aware of.
Here is a pretty good example for a starter a bit heavy on $$
*** WTS *** Remington 700 LSS - 24hourcampfire
Good luck selecting plenty out and about to select from