I've only used the 150 in my 280AI but the IMR7977 (65.3 grains as I recall) works like a charm albeit a tiny bit bulky/slow burning for my application. The case is really FULL and very compressed but shoots in the 3's, to 5's without breaking a sweat. Never has shot over MOA from zero to 800 yards and everything in between.
I worked up my best 270 WSM load with the same powder and stopped at 72 grains but back it off and settled on 71. I now shoot it in 280AI, 7mm Rem mag and 270 WSM. I think I like it!
I went with that powder since it's suppose to be temp insensitive.
Good luck to you Tikka and let us know what you come up with that works for you since many of us shoot 280AI's.
Zeke