Re: How much of the neck to size??
It also depends on what the ammo is used for, and how much neck tension you are using. For example, I wouldn't neck size less than half the neck with .001-.002 neck tension for hunting or tactical matches. It's too light, and the bullet can shift on you. If you're bench shooting only, then it should be alright.
I neck size almost all the way to the shoulder, and run .002 in my 260, and .002-.004 (depending on which bullet) in my 300 WM.