First- you need to get a headspace gauge (I like the Hornady) so you know what you're dealing with.
Then, do what PAJoe suggested.
I had the identical problem when I first got my Hornady LNL. I could not get the shoulder bumped back .002 from the fire-formed dimension. Everyone else was suggesting to send the die back to Hornady and have them grind the base (and even Hornady said that).
Then someone else suggested going past "contact" with the shellplate- so that the press cams over hard- and that took all the "slack" out of the press and solved the problem. No grinding required...
Remember, we're only talking about a few thou here, and it doesn't take much.