Seems to me if the hammer stops the thickness of a cap away from the nipple, it will likely fail to ignite the cap.
I'm happy with .005 or less. One problem is the nipple holes are not always the same depth in all six chambers. You can take a little material off the nose of the nipple, but then it needs to go in that same hole, pita if you pull all six when cleaning. I have had to spot face the nipple seats on some cylinders. You can use a cleaning regiment of only removing one nipple at a time or not remove them at all. What ever works best for you. Maybe be my luck but it seems Remington clones are always the most work.