Shot a doe at 322yds with my 7mm08 last season. Shot high the first time, my fault for not ranging her and using the correct hold over. Second shot was straight into the neck as she faced me. Stone dead when she hit the dirt for her nap. I'd stretch out given the right conditions and rest but not much further.
My neighbors son went to a long range school in Arizona, came back an put his new skills to work. He killed a hog a few days ago at 636yds with a 260.