Mike, we took one of these "portable" buildings, made reloading benches on each side, then put windows in the front to shoot out of with 1.5" plywood tops, 1.5" floor, added incredible insulation, heat, and AC. We shoot in all kinds of weather.
My non-trued 700s are in good stocks, and good glass shoots are incredible. When groups get 1/2", I am looking for the load to have lost its tune, throat wear, etc. I do have customs in 6 PPC, 6 BR, and a flock of BR variants with multiple barrels per action to compare. Replacement of the firing pin/spring and custom recoil lug is as far as I will go.
Alignment with the bore Axis/throat is where much of the accuracy starts and ends, and we proved this on a variety of different kinds of actions that were never trued.
If you have disposable income, buy a custom action for the joy and pride of ownership. I like the custom actions that have proven to be tried and true and whose owners have a well-known reputation for honesty and integrity, Borden, Stolle, and Bat are my personal favorites.
Guys that can reload at the rifle range, out of the camper shell on their truck, pull behind trailer, separate table etc, tune their barrels' accuracy to an incredible level....I cannot stress this enough. Many men never think of reloading at the rifle range, it is a very different mindset, and those who think outside the box on this issue, see HUGE dividends on the first trip to the range!