I was wondering how a 150gr bullet would hold up in a .300 win mag.

Depends on what bullet you are talking about.

A plane bullet like a core lokt, SST, balistic tip will have very rapid to explosive expansion and cause an extreme ammount of trauma and likley mess up a good deal of meat.

A bullet like the TBBC, Barnes, Failsafe will stay together and make a good mushroom and mess up much less meat.

Personally out of a 300 mag of any kind I feel that a bonded bullet (Accubond, Interbond, A-Frame) is a better choice for all types of game. On deer and pronghorn size animals it gives good reliable expansion to create a good wound channel but holds together to keep meat loss down and on larger game like elk and moose it does the above pluss it holds together and retains a high percentage of weight to penetrate deep into the vitals.

I think that the plane style bullets are better suited to velocites below 3000 fps.

big bulls was on the money here, but why use the 150's the 180's with a premium bullet are the way to go w/ the 300winmag, shoot flat and give you better downrange energy. Just my thoughts.