I've shot (for record) a 4.1" group with the 6.5-284 in 1K BR

My hunting 6.5X284's never could do that.

I've shot 1" groups at 550 yards with my huntnig weight 6.5-06's

I really don't think accuracy goes to one or the other. I feel the accuracy is in fact directly related to this.

The smith
The barrel
The hand load
The nut behind the wheel