Accuracy is a lot more complicated than barrel and cartridge, so no guarantees, but yes, the 6.8 or the 6.5 will kill deer if well placed at 200yrds, using the right bullet. (Lots of modifiers there, if you didn't notice).

I ran a 6.5G before the AA fall out and things got hairy (wasn't interested in playing games with the 264LBC or any of that jazz), so I swapped over to the 6.8SPCII. Been quite happy with both. Really bought these to be coyote rifles, but they've done well as deer rifles. I've only used them on meat hunts. The moderate velocity of these in heavier bullets keeps them pretty kind to fur, but still penetrates well enough to kill deer cleanly.

I wouldn't have issue taking deer at 350, maybe a push to consider 400yrds if I had to.