Moman, don't wast your time with Remington or Winchester brass. Spend the money on Norma Brass. Norma brass will;
1. Allow you to shoot higher pressure loads for higher velocity and better performance.
2. Allow for less time prepping brass.
3. Last longer, you get about 9 to 10 firings with Norma 270 WSM. You will only get about 3 to 4 firings with Winchester or Remington brass before it turns to junk.
4. Allow your rifle to shoot more accurately.
5. Much better consistancy
I am not saying Remington or Winchester wont work, it will, just not as good as Norma Brass. If you use Remington or Winchester brass, you will have to spend a bunch of time, cleaning necks, uniforming flash holes, uniforming primer pockets, trimming, ect.
Remington and Winchester have been falling down on the QC (Quality Control). I would highly recommend Norma Brass, and I bet you will get much better results. Sure, it's going to cost more up front but it will be cheaper and worth it in the long run.
You can get Norma 270 WSM Brass, at MidwayUSA, for $94.00 for a box of 100. I know it's $40.00 more than the Winchester or Remington brass, but it's worth it.