Which gun to start with?

[J]

The A-Bolt is a surprisingly nice gun out of the box. Way better than most 700s in stock form IMHO. Parts aren't easy to find for it, but the trigger is adjustable down to the 2-3lb area with a good clean break. The twist rates are almost always on the fast side in the A-Bolt (which are hard to find in most calibers/models of 700s), which is good for the heavier loads you will want to shoot for long range. Stock form, I'd take an A Bolt over just about any 700... but the 700 has so many parts, barrels, and data/knowledge that it can easily be made into a nicer long range setup. That said, given your current needs and desires, you have my vote for the browning.

I'd say invest in a good tactical scope, 20 MOA base (if you want to stretch further than 800), good rings, and pull the trigger out of the stock and crank the set screw out for a lighter pull. You should have no issues pushing a 7mmRM A Bolt out to your desired distances, or even a good bit further with that right there.