I too reload for the 270 win. Sierra's manual, like the Lyman, list an accuracy load and hunting load. I suppose the hunting load might give up a small amount of accuracy for top velocity. Anyway, Sierra lists Reloader 22 as the powder of choice for both accuracy and hunting. That's certainly promising.
You'll also notice in your manual, the ten or so powders listed are sorted by I believe burn rate and the amount of charge required to give a specific velocity. This is strictly hunch - but all other things being equal I would pick powders two/three or so powders evenly spaced in the list, so that if you're trying more than one powder you're getting enough of a difference to matter. Of course if you're loading for another caliber as well, being cross compatible is more important.
Couple other tidbits of advice...
The most accurate load is usually not the fastest load - at least for me. Don't be afraid to try charges equally spaced, throughout the useable range of charge/velocity. In 270, I start 1 grain apart and further refine by .3 grains based on results of the first test. Without looking at the book I might try charges like 51.2, 52.2, 53.2, 54.2, 55.2 to start.
I have found it best to stick with one quality primer. When I have needed to change primers (no stock for example), I usually have to fine tune the load again but can regain the accuracy I had with the previous primer.
As a handloader you have the ability to make cartridges as long or short as you wish. Getting the bullet closer to the lands usualy results in better accuracy while causing higher pressure too. Might be a good idea to google this topic. Try googling "seating lands COL"
Above all else, I have found that the brand and weight of the bullet play the biggest role in accuracy. Sierra has been very good to me, so has Hornady. Others have found their rifles like Noslers or another brand. No way to tell without experimenting.
Good luck, and try not to get addicted to accuracy beyond what is practical.