Bones,
I don't know exactly where to start and I'm not sure I have the energy to finish.
The 270wsm is one of my favorite cartridges. Bullet selection is adequate for reloaders but I have zero experience with factory ammo since about 1969.
You're barking up the right tree. If you're using it for dual purpose then go bigger than smaller bullet weights. 140-150 shoukld be OK.
I've killed a traincar load of deer with one or the other of the 2 that I own but elect to use a bigger caliber for elk.
It's GENERALLY accepted that the .277 is just big enough for elk. I'd say it's just fine and I would not hesitate using one. Evidently you feel the same way.
It's also generally accepted that a bullet should strike with about 1800 ft lbs, at least, and a remaining velocity of 1800 fps. A quick check of the ballistics tables should tell you the cartridge's MAX effective range.
Your maximum effective range is another story altogether. If you can keep 5 shots inside a 8" circle at 650 yards, under field conditions, then you MIGHT be qualified to drop the hammer on a buck at that range. (I guess this is the lecture section)
I like the bullets (projectiles) that you mentioned and have used them in the short mag and the 270 win on a variety of game. Partition, AB, Barnes X are my bullets of choice. The higher BC bullets will have a SLIGHT edge for trajectory within real-world hunting ranges (by slight I mean an inch or two) so it's a no-big-deal IMHO. With rangefinders and lots of time at the range you'll shoot circles around a guy who pins all his hope on his new high BC bullets. Again, just my opinion.
Ok, I'm out of energy. Go buy some ammo and give it a whirl. If it shoots nice tiny groups then go out and buy all the same lot that you can get you hands on. When that doesn't work, give me a shout.
Whew!
Zeke