First, please release the CAP'S LOCK, it makes your post hard to read.
The sizing die reduces the size of the neck so that when you seat the bullet the tension will hold the bullet in place.
I don't reload 270 but the numbers SOUND correct.
With a little lube inside the neck the expander ball should last a long time. I have never worn one out.
You'd be suprised just how much you can screw up just resizing!! I know this for fact! :oops:
A GOOD reloading manual will explain what's happening and why it's happening at every step and what some of the more common mistakes are, why they are occuring and how to correct them.