The 700 is a fine place to start if you are looking to build an accurate hunting rifle at a reasonable price.
However, if you are looking for record-setting benchrest accuracy you would be best served by starting with a BR action. The hottest action in BR now is the BAT. A BAT action is very stiff, all steel and can be had with a magazine cut. Be prepared to pay about $1,300 for the action alone if you go this route.
You might be able to build a rifle that can shoot an ag of 1 moa or a bit better at 600 if you build on a 700 action. Small groups are possible with quite a few rifles, but rifles and shooters that shoot small ags are rare.