Interesting (although not surprising) that the handloads were nearly twice as accurate as the factory loads. I would imagine that there are other factory loads out there that would group as well as the handloads - it's just a matter of finding the right factory load.
Still, your new rifle achieves good very good accuracy with your handloads. Congrats on the rifle.
On a side note, you may also want to post your experience with your Mueller scope on the optics forum. I'm sure that many members would appreciate your scope report.
Zachary