A lot of different topics are discussed on this forum and I'm certainly no expert on any of them, but I have quite a bit of experience with the Sierra 150-grain BTSP "Game King" in several rifles chambered in .270 Winchester, both mine and my Son's. Over the years, since around 1979, I've used that bullet almost exclusively for Pronghorn and Mule Deer in Nevada. This bullet in my Grandfather's old Remington is the reason I stopped hunting with rifles chambered in .308 and .30-06. I was amazed at the terminal results I've obtained with many different shots, from under 100 yards to my last Muley Buck two weeks ago at 510 yards. Most of the kills were clean "bang-flops" but in some cases a big Buck might run 40 yards or so after the Sierra had completely wrecked their boiler room. Large Mule Deer can be very tough animals, and of course even with proper shot placement they will sometimes "kick" and bolt for a couple of seconds before piling up. I recommend these Sierra bullets enthusiastically.
I do recommend, from my family's experiences, you should do your best not to hit shoulder on the way in, as you sometimes will do with a quartering-toward shot. I'd not recommend that angle with any bullet, as you'll necessarily lose some nice shoulder meat. With that situation, especially at close ranges, the Sierra will come apart sooner than you'd like and it's unlikely you'll get any exit. If you can wait for an angle change, broadside hits tight against the shoulders are devastating and make fast kills. The best results we've had were with quartering-away shots when you can hold back into the ribs just a bit away from the near shoulder and have the Sierra punch the lungs and exit through the far-side shoulder. They go down immediately and stay down with those shots. As many on this site have correctly documented, shot placement is very important, regardless of bullet brand and caliber. Happy Hunting!!