I am going to Colorado for my first elk hunt. I have a 338 win mag with a Bushnell 3x9x40 Elite 4200 on it. I thought that this would be fine for Elk size game when hunting (longest shot 400 yards), but a friend said that I should get a 14 or 15 power. I really don't want to change and can't understand how 9X wouldn't be enough . Any thoughts ?