My load is very similar to Jim Watsons.
43 grains of Varget
175 Sierra MK
Federal brass (necks turned, trimmed, primer pockets trued, flash holes done)
CCI BR2 primer
C.O.A.L. .0010 to .0015 off the lands
On the 6mmbr website a national champion says his load is similar to this, but he found that brass and primer were not nearly as important as how far you seated the bullet from the lands. Seating depth is a matter of experimentation to see what your rifle likes.
Another load I have had good luck with:
150 grain Lapua lock base bullet (higher BC than the 165 Sierra MK)
44.5 grains of Reloader 15
CCI BR2, or Federal 210M
Lake City match brass, or Federal Brass. (all brass has been worked as above)
COAL: 2.815
OR:
168 Sierra MK
42.5 Reloader 15
CCI BR2 or Federal 210M
Federal Brass
COAL 2.815
I haven't found any significant difference between my Federal and the lake city brass. I even measured the water weight content and found it to be the same. That surprised me as I had always heard that LC is thicker with less volume capacity. Maybe this lot of LC brass is an oddity, in any case I would sure recommend checking your brass before interchanging such an important (and potentially dangerous) component.