Originally Posted by robin12
If I am wanting to jump into the lands should I shorten the Coal by .10 making the coal 3.280? or do you shorten the case?
I don't think the latter part of your question was adequately addressed.
Your case size is important as follows...
Ideally it has just enough clearance (headspace) to chamber easily/reliably.
When fired, it expands to fill and seal the chamber while launching the bullet.
Then, it springs back slightly so that you can extract the spent case.
When done correctly, full length resizing should bump the shoulder case back about 2-3 thousandths of an inch in order to facillitate easy chambering/extraction in the event things get a little dirty.
But, you don't want the case expanding and contracting too much or the brass will work harden faster, becoming brittle, and split creating a dangerous situation.
So, trim to the "trim to" length shown in your loading manual. And adjust the dies according to the die manufacturer's specification. But, don't alter the case dimensions to tune your load. Rather, adjust seating depth as explained by Azshooter.
Good luck and be safe,