I have a dtech 6x45... wouldn't even think of having any one else build one for me.
I have a couple uppers from dtech. The accuracy and precision from the builds are incredible.
He starts by machining the barrel face on the receiver square. Nobody but precision accuracy builders do that.

The bad part is the year wait on his stuff.

He, Mike, is currently using Shilen match barrel blanks. Before diving into the 6x45 you might consider the 6mmDTI. It is a 6.8SPC necked down for more case capacity than the 6x45. It ought to come close (just shy) to 243 ballistics without having to get into the AR-10 chassis or the WSSM. I had a WSSM so no need here, but just a thought. The 6.5 version is tempting but case length is too long for the VLD bullets.