When would you want to use a 180gr and could you get away with a 150 gr in those situations if need be? I ask this cuz i see people hunting larger game with .270's using a 130 or 140 gr. So a 150 should be a good gr bullet for most things correct?
180 for elk and above! The reason you see people shooting .270's, etc., using lighter bullets is that the lighter bullet in the .270 has greater sectional density than the same weight in the .308" size, so it will penetrate better! You CAN use a 150 grain .30 for larger game, but don't be surprised when it doesn't prform as well on big stuff as the 150 grain in a .270 does!! You'll have to shoot it in exactly the right spot, or shoot it more times!