I use between 45 and 50 pounds of pressure on my gun. That does a good job for me. Not all guns are regulated so you do have to be careful. Mine is the type that you buy from Harbor Freight or Northern Tools -- mine came from Northern.
Dave and Karen -- '02 Ultimate Advantage 36 C, 350 HP Cummins, Allison 3060 Tranny, 2013 Ford Edge, InvisiBrake