Well, hunting big game at 400 is controversial but I will stick with the question. The 338 Win Mag (and its variants) has bullets with pretty good weight and ballistic coeffecients. They retain a ton of energy a long ways out.... if you have a good barrel. (Don't put on a stubby) The bullets also have a larger frontal area. If you try this on game that hunts back, please hunt with a partner and I will feel better.