As Ajo said shot placement will make any bullet work.. Is the reason you want to use a 150gr bullet because your gun shoots the best groups with it or because you like that weight the best? I would step up to the 180gr. Not sure if you have tried a heavier grain bullet in your gun or not.
I'm sure a well placed bullet will do fine, but like others have said here, I go with a 180gr in .30 caliber for Elk as well, leaving the lighter bullets for deer. I happen to use the Nosler Partitions, but get a good penetrating bullet like mentioned above as well.
If you pick up a reloading manual that has a balistic table in it you will find that the magnum calibers were designed to shoot the heaver bullets for better performance of game. The light bullets will work but then why did you buy a magnum rifle speed isn't everything.
Historically, hunting has been a sport that has been predominately participated in by men. There have been notable exceptions, of course. Eleanor O’Connor, wife of the famous hunter and outdoor writer, Jack, traveled with him and hunted in many parts of the world, taking her share of game, including some exceptional trophies. Not as well-known to hunters today were Martin and Osa Johnson of the early to mid-1900’s. Together they traveled to many places that seemed extremely exotic and...