If your not going to reload then considering anything outside the norm is limiting as far as cartridge or chambering. Like wise spending a bunch of money on the custom gun itself seems pointless to me as you your stuck with what the ammo manufacturer's give you, insteadof finding optimal results for your specific gun. The 2 go hand and hand IMHO. Likewise if your looking for the next step to accuracy and custom, then reloading should be the first one to take. Turn your 300wm and anything else you may buy into the shooter you desire. Small relative inexpensive tweeks can be made to any production grade rifle coupled with reloading can find sub MOA loads, tailored to the use. Once you've got to this basis and are confident in your abilities, taking the step to building a custom rifle is a natural one to make allowing you to pick which ever platform/cartidge you desire then rolling your own mo to see its true potential.

If your going to be a factory ammo guyI'd stick with off the rack stuff, thenchoose a cartirdge that has the best options for ammo/application.

JMO