Jerry,
The Eco Tungsten (manufacturer of Nice Shot) website states to add 1500 PSI when replacing lead. One does however need to search for it.
My own experiance is that I encountered "flattened primers" on some early loads which caused me to investigate. I discovered this on the Eco Tungsten Reinventing Lead blog:
"Big Dan said...
Nice Shot is 10.2g/cc a little lighter than magnum lead shot as I stated in earlier posts. What is happening is Nice Shot being a bit harder 14~16 Brinell ( lead 11~13 ) when fired it does not absorb the energy of the acceleration like lead does. Thus causing a slight increase in pressure. This is why we recommend staying 1500 psi lower than the maximum allowable for the gauge you are loading for. And yes, other harder shot alloys will do the same.
June 9, 2009 8:23 PM"
Source:
http://www.blogger.com/comment.g?blogID=4889462393037924104&postID=2282709322412111922Also, from:
http://www.niceshotinc.com/ " "Nice Shot"
has a slightly higher chamber
pressure than an equal lead load.
Precision Reloading's Technical Support will help you with your
loading questions and data. They can be contacted at 605-996-9984
to speak with a technician 8:00 AM – 5:00 PM CST.
Some of their loading data is at Shotgun World."