Lots of bullets will work, your SST might work fine but based on my experience with a 150 NBT blowing up on a bulls ribs I think you are on the right track going to a stout 130-150 grain bullet in your 270.
For me the Barnes TTSX is the best combination of toughness with great accuracy and performance above its weight on elk. I got lucky with my bull and found him after 500 yards through snow because the shrapnel in his lungs finally did him in. A similar angled shot on a bull with TTSX took out lungs, top of the heart and broke the off side shoulder before it exited. No tracking required.
Don't hesitate to get the bullet that shoots best in your rifle, placement trumps bullet construction every time.
