Hey,
I have a Rem. 700 action with a Hart S.S. Fluted barrel combo. The bullet that works the best for me is the Sierra 60gr. HP sitting on top of 43.5 grains of Varget. CCI B.R. primer.
My barrel was formerly a 6BR, My gunsmith had on one of his rifles. He sold and rechambered the barrel for me, so it's now a 6mm Rem. The twist in the barrel will decide on which bullet it likes best. My gunsmith gave me a box of his own custom match bullets in 68 gr. Well, they didn't shoot all that well, when I switched to the Sierra 60's, 4 shots in the same hole at 100 yards.
Try a variety of bullets to find which one shoots the best, just bought a box of 58 gr. V-Maxes, can't wait to try them out
Good Luck with your rifle,
CF