I have been looking at a heavy 6mm build also. Not trying to hijack your thread but have you looked at the 6mm slr. It has caught my attention for a build. anyone have real word experience
I just got a 7.5"twist 26" criterion in 6 SLR on my rifle. So far so good. Ive only shot 110 Matchkings out of it so far. Only .5MOA right now but Im not done tuning.
These were my max speeds, none of which showed pressure but i didnt push the limits.
COAL: 2.920"
H4350: 3110 FPS
H4831SC: 3065 FPS
H1000: 3210 FPS
I went with H1000 and am working in a load around 47.5 grains, 3130 fps ish.
The extra barrel life of the H1000 is a plus as well.