First things first...I have the Larry Willis die....excellent tool. But, I only use it when I NEED to.
Second....What you need to know about FL sizing is this...as you run the brass into the die...to where it starts to squeeze the brass, but not yet bump the sholder...the brass GROWS in length a little. If you never get the sholder to the bump stage in the sizing process, you will have brass that is tight. Most of the problems I see stems from not getting to the sholder bump part of the prcess ... even with the die turned all the way down to the shellholder.
My process. First, dissasemble your bolt and insert the bare bolt back into your gun. Now, when you push your bolt ahead, it will litteraly fall closed with gravity when empty. Now you can feel the contact between boltface and the brass.
Next, grab a bunch of fired casses, back your die out about a turn and run one lubed case through the die. Clean it up, and insert it into the gun. If the bolt won't close, or is stiff, set that brass aside, grab another piece, lube it up, turn the die in a 1/4 turn and size another case. Clean and run it into your chamber. Repeat untill the bolt will litterally fall 1/2 way down, and you need to just lightly touch the bolt to close it. Perfect. Never use the same piece of brass twice...start with a fresh piece of brass.
Now, if your brass is still to long after you have bottomed out the die on the shellholder, then you need to take your die to a machine shop, have them turn .020 off of the die, which should allow you to get to the "sholder bump" part of the process. It,s a 5 min job. Or they can take some off of your shell holder. Either way is fine. I have seen this problem a bunch, and it is a simple fix.
Now, repete the process!!
When you find that perfect setting, lock that die tight and never change it...it will be perfect for that barrel forever. I have more than one gun or barrel in the same caliber, I simply buy another die for that gun (uless it was chambered with the same die by a top smith).
You can always check your work with some scotch tape...just put one layer on the brass where the brass contacts the bolt face...trim it real good and insert the brass.....you should feel a noticeable difference in what it takes to close the bolt. Scotch tape is about .001 - .0015 inches thick.
You are now headspacing off of the sholder, not the belt.
Good luck,
Tod