Re: 300 Win Mag or 338 Lapua
There are so many great choices out there it'll make your head spin if you do not know what you are talking about. Use the search function and READ READ READ. Then after you know a little something about the various cartridge selections, barrel twist, ballistic co-efficients, etc, then ask your question---if you still need to--and then you many actually be able to interpret the advice you receive.
As it stands now, all you will understand is what cartrdige someone else selects for you---what you need to understand is WHY that cartridge will suit you best.
Give a man a fish, he eats for a day, teach a man to fish and he eats for life