My favorite load for two of the 300 RUMs I shoot is the 200 gr Accubond using Retumbo powder. My preference is shooting heavy bullets in big magnums, and especially at the speeds a RUM will produce. With 200 gr Accubonds my loads average 3200 fps and 3257 fps depending on the rifle.
Retumbo...
LOL....Fortunately not using speculation within this thread was limited to animals that were lost/not recovered. Since the deer was in fact found dead I took the liberty to use this exception and speculated to the best of my ability.
My son shot a buck at 600 yards last weekend with a 143 ELDX out of a 6.5 PRC. Perfect lung shot. Buck ran about 20 yards and tipped over dead. Bullet exited, but one interesting thing was there were two exit holes when we skinned him out, one higher mid body and the other coming out through...
Barnes 250 gr TMZ with the blue sabots are what I shoot in my Omega with Blackhorn 209. I mainly use it for deer. If I were going after elk I would also give the 290's a try and then shoot whichever bullet shot the best.