Originally Posted by phorwath
Back the resizing die away from the shell holder until the shoulder is barely set back on the 338 Edge fired case.
This is what I do. With new .338RUM dies and .300RUM brass I set the die far enough down to fully open the neck and contact the shoulder and then slightly back it off so as not to bump the shoulder until it has fully fire formed to my chamber. Then after every firing I keep track of when the bolt meets any resistance, then I set my die to that and ever so slightly bump the shoulder till the bolt meets a faint amount of resistance. Then the die is set for my rifle's chamber.
After every step I run the brass through the rifle to check it's fit. Just make sure to wipe all the lube off before chambering each time.