I replied to your post about my thread on this same caliber in the assorted 6mm's sub forum.
The reasons that I decided to choose this over a 223,which was also under consideration, along with swapping bolt heads and going to 22-250 or 243, etc.)
1) My girlfriend likes shooting this rifle in 204 bcause it's comfortable to her and no recoil. The 204 has low barrel life, I needed something with a long barrel life just in general.
2) The brass used to make 6x45 is incredibly prevalent, I have about 10,000 cases just in my closet and a full 1k of a single lot of FIOCCI brass which isn't that popular at the range. This is the brass I chose to use for the round, dedicated headstamp that I know is a 6x45 instead of a 223.
3) Tube life is much better than a 243, 6PPC, 6BR, etc etc
4) Powder consumption is much lower than the 'overbore' 6's and it likes H335 which I have about 26 lbs of. It shoots the same charge as a 223 essentially.
5) It will shoot light 60 grainers faster than the 223, but it can handle a heavy 105 at the same velocity as a 223 shoots the 90's and the BC's are almost dead even.
6) Back again to no recoil to deal with, even a 243 with 90's in it, she won't like to shoot,no worries about sharing 30-06 ammo with her...)
Instead of a large capacity 6mm I took this for bore life and that I only had to buy a neck die. My 223 dies work for FL resizing the FIOCCHI brass, then neck it up with the 6mm universal die, then seat the bullets with my 223 die. I would have had to buy a full set of expensive dies for anything else.
Total cost of the project, including the reamer, barrel, die, and first box of bullets,75 Vmax) is 240 bucks.