Most would agree that the 270 Win is minimum for Elk
I would not say your 270 Win will not work on Elk, of course it does. It is probibly at the starting end of all the Elk cartridges. If your rifle liked the 150gr load in a controlled expansion bullet you would have more sectional density working for you. The higher the SD the deeper a bullet will penetrate on the animal. I would be tempted to try the 140gr loads sense your rifle doesn't like 150s. I always read you can't go wrong with 180gr loads in a 30-06 for Elk, using a 270Win they usually recommend the 150gr. These two have similar sectional densities. Bottom line stay with a controlled expansion bullet in a weight that your rifle likes. Most important thing is to put that bullet in the right place on the animal.