Once I have completed the load development process, I consider myself to have observed the maximum accuracy level of a given rifle/load combination. I have been fortunate to be able to achieve MOA or less with every bolt action (and one falling block) rifle I own.
Several of my rifles will shoot 1/2" groups or smaller @ 100 yards. One of them shoots consistently in the .3's and has regularly produced five shot groups in the .1's. With that same rifle, I have trouble maintaining 2 MOA @ 600 yards because my ability to cope with wind and mirage is poor.
Personally, I stop load development when I find a load that will repeatably shoot into 1/2" @ 100 yards. I feel it is a better use of my time and components to practice my shooting skills rather than chase smaller groups. .5 MOA will do anything I am looking to do. Several of my rifles will do it easily. The problem is that I am not yet that capable under real world conditions.
.5 MOA that works for me ................I did discover one thing this weekend that when I neck size with the .272 bushing I get a lot better accuracy than when I use the .271 neck sizing bushing...............Im going to check it out more this monday at the range,................