5 shot group will probably be bigger than a 3 shoot group...10 shot bigger than a 5... That was the case with my .280. The more I shot, the bigger the group got. Final measurement for it was 1.342''/10 shot @100 yards. Its my go to hunting rifle (for the time being) and I'm happy with the results. I might tweak it a bit after hunting season. I measured from outer edge to outer edge. Center to center it would be even smaller. If I miss 300 yards and in it won't be the rifles fault. I'm a big fan of the .243 cal. and I think you're on to something. Thanks for sharing the load data with us
