I haven't finished my 6x45 yet but I did a few mock up rounds and it has made me a bit leery. At any sort of 223 mag length be it AR's or a bolt gun mag the heavy bullets are going to be seated way deep, with the 107 probably below the bearing surface. With the 95gr Berger classic hunter I seated at AR mag length the bearing surface is only .015" above the case neck at trim to length. The bullet is seated so deep I'm considering starting bullets right side up and fully seating them in a press mounted upside down so that I can actually get some powder in them without crunching. Even then I think I'm only looking at 2400-2500fps if I'm lucky.
I'm thinking the 6x45 is probably more ideal for lighter bullets at mag length or heavier bullets if single fed. All the numbers I've ran for 6x45 loads show a standard 223 load with 77gr owning it at mag length. The bolt gun loads I've ran the numbers on for the 6x45 my 223AI with 75 AMAX laughs at.
If it wasn't for the fact I want a AR that's hunting legal and I already have all kinds of 223 brass, powder, primers, and 6mm bullets then I would have never entertained it.