Nice, I would go ahead and load up 20 rounds of 46.0 and call it good. I think you did pull that shot on the middle group. But it looks like you've dialed in an OCW node where a +/- 0.3 gr difference in powder charge will still give you sub MOA performance.
Now it is time to play with seating depth to see if you can't tighten the group a tad (your choice), once I get to sub MOA for a tactical rifle I call it good and go shoot.
Machine guns are awesome until you have to carry one.