The heaviest projectile, that shoots well in *your* rifle. Black Hills 77gr loaded with sierra matchkings will likely do the trick. But - at 300 yds max, you could likely go with the Hornady 68's, or SMK 69's and do just about at well. Heavier projectiles are better at wind. Ballistically, its a drop chart, and at those range the load will matter a bit more than the projectile.