I've killed a truckload of deer and pigs with a 6.8 and lots of my hunting buddies use Grendels. As mentioned above, I think they are all pretty similar to a 243 (or maybe a 30-30) in terms of killing power: pretty reliable out to 100 yards, but even getting out to 200 yards you won't always get an exit or very impressive wounding. The Grendel carries energy better than a 6.8 or 300 BLK but none of those rounds with 28-30 grains of propellant capacity kill all that well at longer distances. I think we were all enamored of them for a while but except for pigs we've all since drifted back to cartridges that burn more powder.
Depends on what bullet you're running but at 350 yards, especially out of a 16-18" barrel (most of the published Grendel data is from a 24") I'd expect mild wounding, no exit, and a pretty long dead run.
