When everyone is talking about Nitro's they are not talking about Remington Nitro's.....they are talking about the Nitro ammunition company. Here is their link http://www.nitrocompany.com/
On the website just look up what gun you have and find their suggested load for it.

As for Hevi Shot I would take a look at Hevi-13 3" 2oz #6's, or Hevi-13 3.5" 2.25oz #6's using an Indian Creek .675
Hope that helps.