HighDesertWolf. you may want to reconsider and use a 7mm Rem. Mag. with 160 gr. Sierra Pro Hunter. Your 338 UM will drift 3.2" at 200 and 7.6" at 300 in a 10 mph. breeze. The 7mm Rem. Mag. will drift 2.9" at 200 and 6.8" at 300 and you will have some useable meat after the shot.