I'd much rather always have a faster twist. As always when I end up with a factory 6mm or 224 cal rifle I'm always disappointed and wanting a faster bbl. Never ever had a problem with lighter bullets in fast twist 224 guns.
My custom 1 in 7" twist standard 223 chambered 700 shoots great groups with 50's and great groups with 75 and 77s of all brands.
In 6mm an 80 or 85 Barnes will hammer deer under 350 at anything I've tried over 3,000 fps if you are stuck w a slow twist. Prob most good 75 and 85 sp bullets as well.
Do with a 6.8 all the time with 85s and same range with 75 amax in the 223. Put it in his heart and lungs and they are dead soon enough. Most will pass through when broadside. Other angles I've only had opposite side skin catch em.
They will open at 350 when launched at over 3,000. Even yotes and 40 lb yearling does are enough to open em up completely and pass through at 300-350 and every range in between.
I have shot a bunch of the 85s barnes and should maybe save money and try a cheaper sp as I know they will work, but on a big 250 lb buck quartering away I would rather KNOW the bullet is gonna get to his boiler room. It will.